ALBERT

Description: The origin of the population of very massive stars observed within ∼0.4 pc of the supermassive black hole in the Galactic Centre is a mystery. Tidal forces from the black hole would likely inhibit in situ star formation whilst the youth of the massive stars would seem to exclude formation elsewhere followed by transportation (somehow) into the Galactic Centre. Here, we consider a third way to produce these massive stars from the lower mass stars contained in the nuclear stellar cluster which surrounds the supermassive black hole. A passing gas cloud can be tidally shredded by the supermassive black hole forming an accretion disc around the black hole. Stars embedded within this accretion disc will accrete gas from the disc via Bondi–Hoyle accretion, where the accretion rate on to a star, $dot{M}_star propto M_star ^2$. This super-exponential growth of accretion can lead to a steep increase in stellar masses, reaching the required 40–50 M⊙ in some cases. The mass growth rate depends sensitively on the stellar orbital eccentricities and their inclinations. The evolution of the orbital inclinations and/or their eccentricities as stars are trapped by the disc, and their orbits are circularized, will increase the number of massive stars produced. Thus accretion on to low-mass stars can lead to a top heavy stellar mass function in the Galactic Centre and other galactic nuclei. The massive stars produced will pollute the environment via supernova explosions and potentially produce compact binaries whose mergers may be detectable by the LIGO–VIRGO gravitational waves observatories.

Description: We present a 3D semi-analytical model of self-gravitating discs, and include a prescription for dust trapping in the disc spiral arms. Using Monte Carlo radiative transfer, we produce synthetic ALMA (Atacama Large Millimeter/submillimeter Array) observations of these discs. In doing so, we demonstrate that our model is capable of producing observational predictions, and able to model real image data of potentially self-gravitating discs. For a disc to generate spiral structure that would be observable with ALMA requires that the disc’s dust mass budget is dominated by millimetre- and centimetre-sized grains. Discs in which grains have grown to the grain fragmentation threshold may satisfy this criterion; thus, we predict that signatures of gravitational instability may be detectable in discs of lower mass than has previously been suggested. For example, we find that discs with disc-to-star mass ratios as low as 0.10 are capable of driving observable spiral arms. Substructure becomes challenging to detect in discs where no grain growth has occurred or in which grain growth has proceeded well beyond the grain fragmentation threshold. We demonstrate how we can use our model to retrieve information about dust trapping and grain growth through multiwavelength observations of discs, and using estimates of the opacity spectral index. Applying our disc model to the Elias 27, WaOph 6, and IM Lup systems, we find gravitational instability to be a plausible explanation for the observed substructure in all three discs, if sufficient grain growth has indeed occurred.

Description: The star formation in molecular clouds is inefficient. The ionizing extreme-ultraviolet radiation (hν ≥ 13.6 eV) from young clusters has been considered as a primary feedback effect to limit the star formation efficiency (SFE). Here, we focus on the effects of stellar far-ultraviolet (FUV) radiation (6 eV ≤ hν ≤ 13.6 eV) during the cloud disruption stage. The FUV radiation may further reduce the SFE via photoelectric heating, and it also affects the chemical states of the gas that is not converted to stars (‘cloud remnants’) via photodissociation of molecules. We have developed a one-dimensional semi-analytical model that follows the evolution of both the thermal and chemical structure of a photodissociation region (PDR) during the dynamical expansion of an H ii region. We investigate how the FUV feedback limits the SFE, supposing that the star formation is quenched in the PDR where the temperature is above a threshold value (e.g. 100 K). Our model predicts that the FUV feedback contributes to reduce the SFEs for massive (Mcl ≳ 105 M⊙) clouds with low surface densities ($Sigma _{ m cl}lesssim 100~{ m M}_odot , { m pc}^{-2}$). Moreover, we show that a large part of the H2 molecular gas contained in the cloud remnants should be ‘CO-dark’ under the FUV feedback for a wide range of cloud properties. Therefore, the dispersed molecular clouds are potential factories of CO-dark gas, which returns into the cycle of the interstellar medium.

Description: The Pan-STARRS1 (PS1) 3π survey is a comprehensive optical imaging survey of three quarters of the sky in the grizy broad-band photometric filters. We present the methodology used in assembling the source classification and photometric redshift (photo-z) catalogue for PS1 3π Data Release 1, titled Pan-STARRS1 Source Types and Redshifts with Machine learning (PS1-STRM). For both main data products, we use neural network architectures, trained on a compilation of public spectroscopic measurements that has been cross-matched with PS1 sources. We quantify the parameter space coverage of our training data set, and flag extrapolation using self-organizing maps. We perform a Monte-Carlo sampling of the photometry to estimate photo-z uncertainty. The final catalogue contains 2,902,054,648 objects. On our validation data set, for non-extrapolated sources, we achieve an overall classification accuracy of $98.1\%$ for galaxies, $97.8\%$ for stars, and $96.6\%$ for quasars. Regarding the galaxy photo-z estimation, we attain an overall bias of =0.0005, a standard deviation of σ(Δznorm) = 0.0322, a median absolute deviation of MAD(Δznorm) = 0.0161, and an outlier fraction of $Pleft(|Delta z_{mathrm{norm}}|〉0.15 ight)=1.89\%$. The catalogue will be made available as a high-level science product via the Mikulski Archive for Space Telescopes.

Description: We present CO observations towards a sample of six H i-rich Ultradiffuse galaxies (UDGs) as well as one UDG (VLSB-A) in the Virgo Cluster with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m telescope. CO J = 1–0 is marginally detected at 4σ level in AGC 122966, as the first detection of CO emission in UDGs. We estimate upper limits of molecular mass in other galaxies from the non-detection of CO lines. These upper limits and the marginal CO detection in AGC 122966 indicate low mass ratios between molecular and atomic gas masses. With the star formation efficiency derived from the molecular gas, we suggest that the inefficiency of star formation in such H i-rich UDGs is likely caused by the low efficiency in converting molecules from atomic gas, instead of low efficiency in forming stars from molecular gas.

Description: Diffuse nutrient pollution from agriculture has been the concern of policymakers for several decades, and yet it remains a persistent environmental issue. The current approach to mitigating the problem is predominantly via command and control regulation within the Nitrates Directive and the Water Framework Directive. This article will set out how diffuse pollution can be considered a wicked policy problem which acts as an explanation of how it has eluded the current regulatory regime. It will further establish that the traditional planning process overlooked the complexity of the problem. Finally, it will illustrate the ineffectiveness of the current regulatory framework to mitigate the problem. This will be exemplified through the legal framework of Northern Ireland.

Description: Supermassive black holes (SMBHs) that reside at the centres of galaxies can inject vast amounts of energy into the surrounding gas and are thought to be a viable mechanism to quench star formation in massive galaxies. Here, we study the $10^{9-12.5}, mathrm{M_odot }$ stellar mass central galaxy population of the IllustrisTNG simulation, specifically the TNG100 and TNG300 volumes at z = 0, and show how the three components – SMBH, galaxy, and circumgalactic medium (CGM) – are interconnected in their evolution. We find that gas entropy is a sensitive diagnostic of feedback injection. In particular, we demonstrate how the onset of the low-accretion black hole (BH) feedback mode, realized in the IllustrisTNG model as a kinetic, BH-driven wind, leads not only to star formation quenching at stellar masses $gtrsim 10^{10.5}, mathrm{M_odot }$ but also to a change in thermodynamic properties of the (non-star-forming) gas, both within the galaxy and beyond. The IllustrisTNG kinetic feedback from SMBHs increases the average gas entropy, within the galaxy and in the CGM, lengthening typical gas cooling times from $10!-!100, mathrm{Myr}$ to $1!-!10, mathrm{Gyr}$, effectively ceasing ongoing star formation and inhibiting radiative cooling and future gas accretion. In practice, the same active galactic nucleus (AGN) feedback channel is simultaneously ‘ejective’ and ‘preventative’ and leaves an imprint on the temperature, density, entropy, and cooling times also in the outer reaches of the gas halo, up to distances of several hundred kiloparsecs. In the IllustrisTNG model, a long-lasting quenching state can occur for a heterogeneous CGM, whereby the hot and dilute CGM gas of quiescent galaxies contains regions of low-entropy gas with short cooling times.

Description: We study the stationary points of the hierarchical three body problem in the planetary limit (m1, m2 ≪ m0) at both the quadrupole and octupole orders. We demonstrate that the extension to octupole order preserves the principal stationary points of the quadrupole solution in the limit of small outer eccentricity e2 but that new families of stable fixed points occur in both prograde and retrograde cases. The most important new equilibria are those that branch off from the quadrupolar solutions and extend to large e2. The apsidal alignment of these families is a function of mass and inner planet eccentricity, and is determined by the relative directions of precession of ω1 and ω2 at the quadrupole level. These new equilibria are also the most resilient to the destabilizing effects of relativistic precession. We find additional equilibria that enable libration of the inner planet argument of pericentre in the limit of radial orbits and recover the non-linear analogue of the Laplace–Lagrange solutions in the coplanar limit. Finally, we show that the chaotic diffusion and orbital flips identified with the eccentric Kozai–Lidov mechanism and its variants can be understood in terms of the stationary points discussed here.

Description: Summary On 24th August 2016 at 01:36 UTC a ML6.0 earthquake struck several villages in central Italy, among which Accumoli, Amatrice and Arquata del Tronto. The earthquake was recorded by about 350 seismic stations, causing 299 fatalities and damage with macroseismic intensities up to 11. The maximum acceleration was observed at Amatrice station (AMT) reaching 916 cm/s2 on E-W component, with epicentral distance of 15 km and Joyner and Boore distance to the fault surface (RJB) of less than a kilometre. Motivated by the high levels of observed ground motion and damage, we generate broadband seismograms for engineering purposes by adopting a hybrid method. To infer the low frequency seismograms, we considered the kinematic slip model by Tinti et al. (2016). The high frequency seismograms were produced using a stochastic finite-fault model approach based on dynamic corner-frequency. Broadband synthetic time series were therefore obtained by merging the low and high frequency seismograms. Simulated hybrid ground motions were compared both with the observed ground motions and the ground-motion prediction equations (GMPEs), to explore their performance and to retrieve the region-specific parameters endorsed for the simulations. In the near-fault area we observed that hybrid simulations have a higher capability to detect near source effects and to reproduce the source complexity than the use of GMPEs. Indeed, the general good consistency found between synthetic and observed ground motion (both in the time and frequency domain), suggests that the use of regional-specific source scaling and attenuation parameters together with the source complexity in hybrid simulations improves ground motion estimations. To include the site effect in stochastic simulations at selected stations, we tested the use of amplification curves derived from HVRSs (horizontal-to-vertical response spectra) and from HVSRs (horizontal-to-vertical spectral ratios) rather than the use of generic curves according to NTC-18 Italian seismic design code. We generally found a further reduction of residuals between observed and simulated both in terms of time histories and spectra.

Description: Despite its likely importance in astrochemistry, pure rotational spectra are not observable for gas phase N2 since this molecule has no permanent dipole moment. Complexation of monomeric N2 with a cationic metal (MN2+) may be kinetically and thermodynamically favorable, and the detection of such MN2+ molecules could be useful tracers of N2 in order to probe its abundance and kinetics. Highly accurate quartic force field methods have been applied here to compute rotational and vibrational spectroscopic properties of the NaN2+ and MgN2+ molecules via a coupled cluster-based composite approach with additional corrections for post-CCSD(T) electron correlation and relativistic effects. The relative energies of various isomers have also been computed and show that both NaN2+ and MgN2+ have linear ground electronic states. At the highest level of theory, rotational constants (B0) of 4086.9 and 4106.0 MHz are predicted for NaN2+ and MgN2+, respectively, with dipole moments of 6.92 D and 4.34 D, respectively making them rotationally observable even at low concentrations. Post-CCSD(T) electron correlation corrections lower the N-N stretching frequency while relativistic corrections have a much smaller effect putting the fundamental frequencies at 2333.7 cm−1 and 2313.6 cm−1, respective of NaN2+ and MgN2+ slightly above that in N2H+. Additive corrections do not significantly change the other two vibrational modes. An anharmonic, zero-point corrected N2 dissociation energy of 7.3 and 7.0 kcal mol−1 is, respectively, reported for NaN2+ and MgN2+ suggesting possible formation of these molecules in protoplanetary disks or planetary nebulae that are metal- and nitrogen-rich.

Description: Simulations of galaxy formation tend to place star particles in orbits seriously different from circular in numbers far larger than seem reasonable for the bulges and stellar haloes of the nearby L ∼ L* galaxies that can be examined in particularly close detail. I offer an example of how the situation might be improved: a prescription for non-Gaussian initial conditions on the scale of galaxies.

Description: We present results from six epochs of quasi-simultaneous radio, (sub-)millimetre, infrared, optical, and X-ray observations of the black hole X-ray binary MAXI J1535−571. These observations show that as the source transitioned through the hard–intermediate X-ray state towards the soft–intermediate X-ray state, the jet underwent dramatic and rapid changes. We observed the frequency of the jet spectral break, which corresponds to the most compact region in the jet where particle acceleration begins (higher frequencies indicate closer to the black hole), evolves from the infrared band into the radio band (decreasing by ≈3 orders of magnitude) in less than a day. During one observational epoch, we found evidence of the jet spectral break evolving in frequency through the radio band. Estimating the magnetic field and size of the particle acceleration region shows that the rapid fading of the high-energy jet emission was not consistent with radiative cooling; instead, the particle acceleration region seems to be moving away from the black hole on approximately dynamical time-scales. This result suggests that the compact jet quenching is not caused by local changes to the particle acceleration, rather we are observing the acceleration region of the jet travelling away from the black hole with the jet flow. Spectral analysis of the X-ray emission shows a gradual softening in the few days before the dramatic jet changes, followed by a more rapid softening ∼1–2 d after the onset of the jet quenching.

Description: Summary We explore here the benefits of using constraints from seismic tomography in gravity data inversion and how inverted density distributions can be improved by doing so. The methodology is applied to a real field case in which we reconstruct the density structure of the Pyrenees along a southwest-northeast transect going from the Ebro basin in Spain to the Arzacq basin in France. We recover the distribution of densities by inverting gravity anomalies under constraints coming from seismic tomography. We initiate the inversion from a prior density model obtained by scaling a pre-existing compressional seismic velocity Vp model using a Nafe-Drake relationship : the Vp model resulting from a full-waveform inversion of teleseismic data. Gravity data inversions enforce structural similarities between Vp and density by minimizing the norm of the cross-gradient between the density and Vp models. We also compare models obtained from 2.5D and 3D inversions. Our results demonstrate that structural constraints allow us to better recover the density contrasts close to the surface and at depth, without degrading the gravity data misfit. The final density model provides valuable information on the geological structures and on the thermal state and composition of the western region of the Pyrenean lithosphere.

Description: Summary The relatively short duration of the early stages of subduction results in a poor geological record, limiting our understanding of this critical stage. Here, we utilize a 2D numerical model of incipient subduction, that is the stage after a plate margin has formed with a slab tip that extends to a shallow depth and address the conditions under which subduction continues or fails. We assess energy budgets during the evolution from incipient subduction to either a failed or successful state, showing how the growth of potential energy, and slab pull, is resisted by the viscous dissipation within the lithosphere and the mantle. The role of rheology is also investigated, as deformation mechanisms operating in the crust and mantle facilitate subduction. In all models, the onset of subduction is characterized by high lithospheric viscous dissipation and low convergence velocities, whilst successful subduction sees the mantle become the main area of viscous dissipation. In contrast, failed subduction is defined by the lithospheric viscous dissipation exceeding the lithospheric potential energy release rate and velocities tend towards zero. We show that development of a subduction zone depends on the convergence rate, required to overcome thermal diffusion and to localise deformation along the margin. The results propose a minimum convergence rate of ∼ 0.5 cm yr−1 is required to reach a successful state, with 100 km of convergence over 20 Myr, emphasizing the critical role of the incipient stage.

Description: Summary Although many studies have revealed that the atmospheric effects of electromagnetic wave propagation (including ionospheric and tropospheric water vapor) have serious impacts on Interferometric Synthetic Aperture Radar (InSAR) measurement results, atmospheric corrections have not been thoroughly and comprehensively investigated in many well-known cases of InSAR focal mechanism solutions, which means there is no consensus on whether atmospheric effects will affect the InSAR focal mechanism solution. Moreover, there is a lack of quantitative assessment on how much the atmospheric effect affects the InSAR focal mechanism solution. In this paper, we emphasized that it was particularly important to assess the impact of InSAR ionospheric and tropospheric corrections on the underground nuclear explosion modeling quantitatively. Therefore, we investigated the 4th North Korea (NKT-4) underground nuclear test using ALOS-2 liters-band SAR images. Because the process of the underground nuclear explosion was similar to the volcanic magma source activity, we modeled the ground displacement using the Mogi model. Both the ionospheric and tropospheric phase delays in the interferograms were investigated. Furthermore, we studied how the ionosphere and troposphere phase delays could bias the estimation of Mogi source parameters. The following conclusions were drawn from our case study: The ionospheric delay correction effectively mitigated the long-scale phase ramp in the full-frame interferogram, the standard deviation decreased from 1.83 cm to 0.85 cm compared to the uncorrected interferogram. The uncorrected estimations of yield and depth were 8.44 kt and 370.33 m, respectively. Compared to the uncorrected estimations, the ionospheric correction increased the estimation of yield and depth to 9.43 kt and 385.48 m while the tropospheric correction slightly raised them to 8.78 kt and 377.24 m. There were no obvious differences in the location estimations among the four interferograms. When both corrections were applied, the overall standard deviation was 1.16 cm, which was even larger than the ionospheric corrected interferogram. We reported the source characteristics of NKT-4 based on the modeling results derived from the ionospheric corrected interferogram. The preferred estimation of NKT-4 was a Mogi source located at 129°04′22.35‘E, 41°17′54.57″N buried at 385.48 m depth. The cavity radius caused by the underground explosion was 22.02 m. We reported the yield estimation to be 9.43 kt. This study showed that for large-scale natural deformation sources such as volcanoes and earthquakes, atmospheric corrections would be more significant, but even if the atmospheric signal did not have much complexity, the corrections should not be ignored.

Description: SUMMARY Self-consistent modelling of magmatic systems is challenging as the melt continuously changes its chemical composition upon crystallization, which may affect the mechanical behaviour of the system. Melt extraction and subsequent crystallization create new rocks while depleting the source region. As the chemistry of the source rocks changes locally due to melt extraction, new calculations of the stable phase assemblages are required to track the rock evolution and the accompanied change in density. As a consequence, a large number of isochemical sections of stable phase assemblages are required to study the evolution of magmatic systems in detail. As the state-of-the-art melting diagrams may depend on nine oxides as well as pressure and temperature, this is a 10-D computational problem. Since computing a single isochemical section (as a function of pressure and temperature) may take several hours, computing new sections of stable phase assemblages during an ongoing geodynamic simulation is currently computationally intractable. One strategy to avoid this problem is to pre-compute these stable phase assemblages and to create a comprehensive database as a hyperdimensional phase diagram, which contains all bulk compositions that may emerge during petro-thermomechanical simulations. Establishing such a database would require repeating geodynamic simulations many times while collecting all requested compositions that may occur during a typical simulation and continuously updating the database until no additional compositions are required. Here, we describe an alternative method that is better suited for implementation on large-scale parallel computers. Our method uses the entries of an existing preliminary database to estimate future required chemical compositions. Bulk compositions are determined within boundaries that are defined manually or through principal component analysis in a parameter space consisting of clustered database entries. We have implemented both methods within a massively parallel computational framework while utilizing the Gibbs free energy minimization program Perple_X. Results show that our autonomous approach increases the resolution of the thermodynamic database in compositional regions that are most likely required for geodynamic models of magmatic systems.

Description: The solid material of protoplanetary discs forms an asymmetric pattern around a low-mass planet ($M_mathrm{p}le 10, mathrm{ M}_oplus$) due to the combined effect of dust–gas interaction and the gravitational attraction of the planet. Recently, it has been shown that although the total solid mass is negligible compared to that of gas in protoplanetary discs, a positive torque can be emerged by a certain size solid species. The torque magnitude can overcome that of gas which may result in outward planetary migration. In this study, we show that the accretion of solid species by the planet strengthens the magnitude of solid torque being either positive or negative. We run two-dimensional, high-resolution ($1.5, m {K}imes 3, m {K}$) global hydrodynamic simulations of an embedded low-mass planet in a protoplanetary disc. The solid material is handled as a pressureless fluid. Strong accretion of well-coupled solid species by an $M_mathrm{p}lesssim 0.3, mathrm{ M}_oplus$ protoplanet results in the formation of such a strongly asymmetric solid pattern close to the planet that the positive solid torque can overcome that of gas by two times. However, the accretion of solids in the pebble regime results in increased magnitude negative torque felt by protoplanets and strengthened positive torque for Earth-mass planets. For $M_mathrm{p}ge 3, mathrm{ M}_oplus$ planets, the magnitude of the solid torque is positive, however, independent of the accretion strength investigated. We conclude that the migration of solid accreting planets can be substantially departed from the canonical type-I prediction.

Description: The coma of comet 67P/Churyumov–Gerasimenko has been probed by the Rosetta spacecraft and shows a variety of different molecules. The ROSINA COmet Pressure Sensor and the Double Focusing Mass Spectrometer provide in situ densities for many volatile compounds including the 14 gas species H2O, CO2, CO, H2S, O2, C2H6, CH3OH, H2CO, CH4, NH3, HCN, C2H5OH, OCS, and CS2. We fit the observed densities during the entire comet mission between 2014 August and 2016 September to an inverse coma model. We retrieve surface emissions on a cometary shape with 3996 triangular elements for 50 separated time intervals. For each gas, we derive systematic error bounds and report the temporal evolution of the production, peak production, and the time-integrated total production. We discuss the production for the two lobes of the nucleus and for the Northern and Southern hemispheres. Moreover, we provide a comparison of the gas production with the seasonal illumination.

Description: We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range [M* ∼ (2–5) × 1010 M⊙]. This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that both size and Sérsic index are better predictors of halo mass than either colour or SSFR, with the data showing a slight preference for Sérsic index. In other words, we find that mean halo mass is more tightly correlated with galaxy structure than either past star formation history or current star formation rate. Our results lead to an approximate lower bound on the dispersion in halo masses among log M* ≈ 10.5 galaxies: We find that the dispersion is ≳0.3 dex. This would imply either that offsets from the mean SHMR are closely coupled to size/structure or that the dispersion in the SHMR is larger than what past results have suggested. Our results thus provide new empirical constraints on the relationship between stellar and halo mass assembly at this particularly interesting mass range.

Description: We perform a comparative study between the only radio-detected Type I superluminous supernova (SLSN) PTF10hgi, and the most active repeating fast radio burst FRB121102. This study has its root in the hypothesized FRB-SLSN connection that states that magnetars born in SLSN can power FRBs. The wide-band spectrum (0.6–15 GHz) of PTF10hgi presented here, provides strong evidence for the magnetar wind nebular origin of the radio emission. The same spectrum also enables us to make robust estimates of the radius and the magnetic field of the radio-emitting region and demonstrates that the nebula is powered by the rotational energy of the magnetar. This spectrum is then compared with that of FRB121102 which we extend down to 400 MHz using archival data. The newly added measurements put very tight constraint on the emission models of the compact persistent source associated with FRB121102. We find that while both sources can be powered by the rotational energy of the underlying magnetar, the average energy injection rate is much higher in FRB121102. Hence, we hypothesize that, if PTF10hgi is indeed emitting fast radio bursts, those will be much weaker energetically than those from FRB121102.

Description: We propose a new intuitive metric for evaluating the tension between two experiments, and apply it to several data sets. While our metric is non-optimal, if evidence of tension is detected, this evidence is robust and easy to interpret. Assuming a flat ΛCDM cosmological model, we find that there is a modest 2.2σ tension between the DES Year 1 results and the Planck measurements of the Cosmic Microwave Background (CMB). This tension is driven by the difference between the amount of structure observed in the late-time Universe and that predicted from fitting the Planck data, and appears to be unrelated to the tension between Planck and local estimates of the Hubble rate. In particular, combining DES, Baryon Acoustic Oscillations (BAO), Big-Bang Nucleosynthesis (BBN), and supernovae (SNe) measurements recovers a Hubble constant and sound horizon consistent with Planck, and in tension with local distance-ladder measurements. If the tension between these various data sets persists, it is likely that reconciling all current data will require breaking the flat ΛCDM model in at least two different ways: one involving new physics in the early Universe, and one involving new late-time Universe physics.

Description: Transformation of refractory cratonic mantle into more fertile lithologies is the key to the fate of cratonic lithosphere. This process has been extensively studied in the eastern North China Craton (NCC) while that of its western part is still poorly constrained. A comprehensive study of newly-found pyroxenite xenoliths from the Langshan area, in the northwestern part of this craton is integrated with a regional synthesis of pyroxenite and peridotite xenoliths to constrain the petrogenesis of the pyroxenites and provide an overview of the processes involved in the modification of the deep lithosphere. The Langshan pyroxenites are of two types, high-Mg# [Mg2+/(Mg2++Fe2+)*100 = ∼ 90, atomic ratios] olivine-bearing websterites with high equilibration temperatures (880 ∼ 970 oC), and low-Mg# (70 ∼ 80) plagioclase-bearing websterites with low equilibration temperatures (550 ∼ 835 oC). The high-Mg# pyroxenites show trade-off abundances of olivine and orthopyroxene, highly depleted bulk Sr-Nd (ƐNd = +11.41, 87Sr/86Sr = ∼0.7034) and low clinopyroxene Sr isotopic ratios (mean 87Sr/86Sr = ∼0.703). They are considered to reflect the reaction of mantle peridotites with silica-rich silicate melts derived from the convective mantle. Their depletion in fusible components (e.g., FeO, TiO2 and Na2O) and progressive exhaustion of incompatible elements suggest melt extraction after their formation. The low-Mg# pyroxenites display layered structures, convex-upward rare earth element patterns, moderately enriched bulk Sr-Nd isotopic ratios (ƐNd = -14.20 ∼ -16.74, 87Sr/86Sr = 0.7070 ∼ 0.7078) and variable clinopyroxene Sr-isotope ratios (87Sr/86Sr = 0.706-0.711). They are interpreted to be crustal cumulates from hypersthene-normative melts generated by interaction between the asthenosphere and heterogeneous lithospheric mantle. Combined with studies on regional peridotite xenoliths, it is shown that the thinning and refertilization of the lithospheric mantle was accompanied by crustal rejuvenation and that such processes occurred ubiquitously in the northwestern part of the NCC. A geodynamic model is proposed for the evolution of the deep lithosphere, which includes long-term mass transfer through a mantle wedge into the deep crust from the Paleozoic to the Cenozoic, triggered by subduction of the Paleo-Asian ocean and the Late Mesozoic lithospheric extension of eastern Asia.

Description: Fishermen are known to try to avoid fishing in stormy weather, as storms pose a physical threat to fishers, their vessels, and their gear. In this article, a dataset and methods are developed to investigate the degree to which fishers avoid storms, estimate storm aversion parameters, and explore how this response varies across vessel characteristics and across regions of the United States. The data consist of vessel-level trip-taking decisions from six federal fisheries across the United States combined with marine storm warning data from the National Weather Service. The estimates of storm aversion can be used to parameterize predictive models. Fishers’ aversion to storms decreases with increasing vessel size and increases with the severity of the storm warning. This information contributes to our understanding of the risk-to-revenue trade-off that fishers evaluate every time they consider going to sea, and of the propensity of fishers to take adaptive actions to avoid facing additional physical risk.

Description: There is currently a severe discrepancy between theoretical models of dust formation in core-collapse supernovae (CCSNe), which predict $gtrsim 0.01 , { m M}_odot$ of ejecta dust forming within ∼1000 d, and observations at these epochs, which infer much lower masses. We demonstrate that, in the optically thin case, these low dust masses are robust despite significant observational and model uncertainties. For a sample of 11 well-observed CCSNe, no plausible model reaches carbon dust masses above $10^{-4} , { m M}_odot$, or silicate masses above $sim 10^{-3} , { m M}_odot$. Optically thick models can accommodate larger dust masses, but the dust must be clumped and have a low (

Description: Sardine Sardinops sagax is an ecologically and economically important Clupeid found off the entire South African coast that includes both coastal upwelling and western boundary current systems. Although the management of the sardine fisheries historically assumed a single, panmictic population, the existence of three, semi-discrete subpopulations has recently been hypothesized. We conducted otolith δ18O and microstructure analyses to investigate nursery habitat temperatures and early life growth rates, respectively, of sardine collected from three biogeographic regions around South Africa’s coast to test that hypothesis. Analyses indicated that for both summer- and winter-captured adults and summer-captured juveniles, fishes from the west coast grew significantly slower in water that was several degrees cooler than those from the south and east coasts. This suggests that mixing of sardines between regions, particularly the west and other coasts, is relatively limited and supports the hypothesis of semi-discrete subpopulations. However, the west-south differences disappeared in the results for winter-captured juveniles, suggesting that differences in early life conditions between regions may change seasonally, and/or that all or most winter-captured juveniles originated from the west coast. Further elucidating the interactions between South African sardine subpopulations and the mechanisms thereof is important for sustainable harvesting of this species.

Description: We study the relation between the UV slope, β, and the ratio between the infrared- and UV luminosities (IRX) of galaxies from TNG50, the latest installment of the IllustrisTNG galaxy formation simulations. We select 7280 star-forming main-sequence (SFMS) galaxies with stellar mass ≥109 M⊙ at redshifts 0 ≤ z ≤ 4 and perform radiative transfer with skirt to model effects of interstellar medium dust on the emitted stellar light. Assuming a Milky Way dust type and a dust-to-metal ratio of 0.3, we find that TNG50 SFMS galaxies generally agree with observationally derived IRX–β relations at z ≲ 1. However, we find a redshift-dependent systematic offset with respect to empirically derived local relations, with the TNG50 IRX–β relation shifting towards lower β and steepening at higher redshifts. This is partially driven by variations in the dust-uncorrected UV slope of galaxies, due to different star formation histories of galaxies selected at different cosmic epochs; we suggest the remainder of the effect is caused by differences in the effective dust attenuation curves of galaxies as a function of redshift. We find a typical galaxy-to-galaxy variation of 0.3 dex in infrared excess (IRX) at fixed β, correlated with intrinsic galaxy properties: galaxies with higher star formation rates, star formation efficiencies, gas metallicities and stellar masses exhibit larger IRX values. We demonstrate a degeneracy between stellar age, dust geometry, and dust composition: z = 4 galaxies with a Small Magellanic Cloud dust type follow the same IRX–β relation as low-redshift galaxies with MW dust. We provide a redshift-dependent fitting function for the IRX–β relation for MW dust based on our models.

Description: There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.

Description: Tilted and warped discs inside tilted dark matter haloes are predicted from numerical and semi-analytical studies. In this paper, we use deep imaging to demonstrate the likely existence of tilted outer structures in real galaxies. We consider two SB0 edge-on galaxies, NGC 4469 and NGC 4452, which exhibit apparent tilted outer discs with respect to the inner structure. In NGC 4469, this structure has a boxy shape, inclined by ΔPA ≈ 3° with respect to the inner disc, whereas NGC 4452 harbours a discy outer structure with ΔPA ≈ 6°. In spite of the different shapes, both structures have surface brightness profiles close to exponential and make a large contribution (∼30 per cent) to the total galaxy luminosity. In the case of NGC 4452, we propose that its tilted disc likely originates from a former fast tidal encounter (probably with IC 3381). For NGC 4469, a plausible explanation may also be galaxy harassment, which resulted in a tilted or even a tumbling dark matter halo. A less likely possibility is accretion of gas-rich satellites several Gyr ago. New deep observations may potentially reveal more such galaxies with tilted outer structures, especially in clusters. We also consider galaxies, mentioned in the literature, where a central component (a bar or a bulge) is tilted with respect to the stellar disc. According to our numerical simulations, one of the plausible explanations of such observed ‘tilts’ of the bulge/bar is a projection effect due to a not exactly edge-on orientation of the galaxy coupled with a skew angle of the triaxial bulge/bar.

Description: We report the discovery of a bar, a pseudo-bulge, and unresolved point source in the archetype collisional ring galaxy Cartwheel using careful morphological analysis of a near-infrared (NIR) Ks-band image of excellent quality (seeing = 0.42″) at the ESO archive. The bar is oval-shaped with a semi-major axis length of 3.23″ (∼2.09 kpc), with almost a flat light distribution along it. The bulge is almost round (ellipticity = 0.21) with an effective radius of 1.62″ (∼1.05 kpc) and a Sersic index of 0.99, parameters typical of pseudo-bulges in late-type galaxies. The newly discovered bar is not recognizable as such in the optical images even with more than a factor of 2 higher spatial resolution of the Hubble Space Telescope, due to a combination of its red colour and the presence of dusty features. The observed bar and pseudo-bulge most likely belonged to the pre-collisional progenitor of the Cartwheel. The discovery of a bar in an archetype collisional ring galaxy Cartwheel is the first observational evidence to confirm the prediction that bars can survive a drop-through collision along with the morphological structures like a central bulge (pseudo).

Description: We report the results of optical follow-up observations of 29 gravitational-wave (GW) triggers during the first half of the LIGO–Virgo Collaboration (LVC) O3 run with the Gravitational-wave Optical Transient Observer (GOTO) in its prototype 4-telescope configuration (GOTO-4). While no viable electromagnetic (EM) counterpart candidate was identified, we estimate our 3D (volumetric) coverage using test light curves of on- and off-axis gamma-ray bursts and kilonovae. In cases where the source region was observable immediately, GOTO-4 was able to respond to a GW alert in less than a minute. The average time of first observation was 8.79 h after receiving an alert (9.90 h after trigger). A mean of 732.3 square degrees were tiled per event, representing on average 45.3 per cent of the LVC probability map, or 70.3 per cent of the observable probability. This coverage will further improve as the facility scales up alongside the localization performance of the evolving GW detector network. Even in its 4-telescope prototype configuration, GOTO is capable of detecting AT2017gfo-like kilonovae beyond 200 Mpc in favourable observing conditions. We cannot currently place meaningful EM limits on the population of distant ($hat{D}_L = 1.3$ Gpc) binary black hole mergers because our test models are too faint to recover at this distance. However, as GOTO is upgraded towards its full 32-telescope, 2 node (La Palma & Australia) configuration, it is expected to be sufficiently sensitive to cover the predicted O4 binary neutron star merger volume, and will be able to respond to both northern and southern triggers.

Description: The orogenic development after the continental collision between Laurussia and Gondwana, led to two contrasting associations of mantle-derived magmatic rocks on the territory of the Bohemian Massif: (i) a 340–310 Ma lamprophyre-lamproite orogenic association and (ii) a 300–275 Ma lamprophyre association of anorogenic affinity. Major types of potassic mantle-derived magmatic rocks recognised in the orogenic and anorogenic associations include: (i) calc-alkaline to alkaline lamprophyres, (ii) alkaline “orthopyroxene minettes” (and geochemically related rocks), and (iii) peralkaline lamproites. These three types significantly differ with respect to mineral, whole-rock and Sr–Nd–Pb–Li isotope composition, and spatial distribution. The calc-alkaline lamprophyres occur throughout the entire Saxo-Thuringian and Moldanubian zones, whereas the different types of malte-derived potassic rocks are spatially restricted to particular zones. Rocks of the Carboniferous lamprophyre-lamproite orogenic association are characterised by variable negative εNd(i) and variably radiogenic Sr(i), whereas the rocks of the Permian lamprophyre association of anorogenic affinity are characterised by positive εNd(i) and relatively young depleted-mantle Nd-model ages reflecting increasing input from upwelling asthenospheric mantle. The small variation in the Pb isotopic composition of post-collisional potassic mantle-derived magmatic rocks (of both the orogenic and anorogenic series) implies that the Pb budget of the mantle beneath the Bohemian Massif is dominated by the same crust-derived material, which itself may include material derived from several sources. The source rocks of “orthopyroxene minettes” are characterised by isotopically light (“eclogitic”) Li and strongly radiogenic (crustal) Sr and may have been metasomatised by high-pressure fluids along the edge of a subduction zone. In contrast, the strongly Al2O3 and CaO depleted mantle source of the lamproites is characterised by isotopically heavy Li and high SiO2 and extreme K2O contents. This mantle source may have been metasomatised predominantly by melts. The mantle source of the lamprophyres may have undergone metasomatism by both fluids and melts.

Description: In this work, we investigate configuration formation of two inner terrestrial planets near mean motion resonance (MMR) induced by the perturbation of a distant gas giant for the Kepler-68 system, by conducting thousands of numerical simulations. The results show that the formation of terrestrial planets is relevant to the speed of type I migration, the mass of planets, and the existence of giant planet. The mass and eccentricity of the giant planet may play a crucial role in shaping the final configuration of the system. The inner planet pair can be trapped in 5:3 or 7:4 MMRs if the giant planet revolves the central star with an eccentric orbit, which is similar to the observed configuration of Kepler-68. Moreover, we find that the eccentricity of the middle planet can be excited to roughly 0.2 if the giant planet is more massive than 5 MJ; otherwise, the terrestrial planets are inclined to remain in near-circular orbits. Our study may provide a likely formation scenario for the planetary systems that harbour several terrestrial planets near MMRs inside and one gas giant exterior to them.

Description: The recent emergence of Olive Quick Decline Syndrome in Italy, caused by Xylella fastidiosa, has drawn attention to the risks posed by this vector-borne bacterium to important crops in Europe (especially fruit trees and grapevine). Comparatively very little is known on actual and potential impacts of this pathogen in forests, in the native (North American) and introduced (European) regions, respectively. The present review aims to address important questions related to the threat posed by X. fastidiosa to European forests, such as the following: What are the symptoms, hosts and impact of bacterial leaf scorch caused by X. fastidiosa on trees in North America? Which forest tree species have been found infected in the introduction area in Europe? How does X. fastidiosa cause disease in susceptible hosts? Are there any X. fastidiosa genotypes (subspecies and sequence types) specifically associated with forest trees? How is X. fastidiosa transmitted? What are the known and potential vectors for forest trees? How does vector ecology affect disease? Is the distribution of X. fastidiosa, especially the strains associated with trees, restricted by climatic factors? Is disease risk for trees different in forest ecosystems as compared with urban settings? We conclude by pointing to important knowledge gaps related to all these questions and strongly advocate for more research about the Xylella-forest pathosystems, in both North America and Europe.

Description: In recent years, a new window on galaxy evolution opened, thanks to the increasing discovery of galaxies with a low-surface brightness, such as Ultra Diffuse Galaxies (UDGs). The formation mechanism of these systems is still a much debated question and so are their kinematical properties. In this work, we address this topic by analysing the stellar kinematics of isolated UDGs formed in the hydrodynamical simulation suite Numerical Investigation of a Hundred Astrophysical Objects (NIHAO). We construct projected line-of-sight velocity and velocity dispersion maps to compute the projected specific angular momentum, λR, to characterize the kinematical support of the stars in these galaxies. We found that UDGs cover a broad distribution, ranging from dispersion to rotation-supported galaxies, with similar abundances in both regimes. The degree of rotation support of simulated UDGs correlates with several properties such as galaxy morphology, higher H i fractions, and larger effective radii with respect to the dispersion-supported group, while the dark matter halo spin and mass accretion history are similar among the two populations. We demonstrate that the alignment of the infalling baryons into the protogalaxy at early z is the principal driver of the z = 0 stellar kinematic state: pressure-supported isolated UDGs form via misaligned gas accretion while rotation-supported ones build up their baryons in an ordered manner. Accounting for random inclination effects, we predict that a comprehensive survey will find nearly half of field UDGs to have rotationally supported stellar discs, when selecting UDGs with effective radius larger than 1 kpc.

Description: SUMMARY We present a statistical rock physics inversion of the elastic and electrical properties to estimate the petrophysical properties and quantify the associated uncertainty. The inversion method combines statistical rock physics modeling with Bayesian inverse theory. The model variables of interest are porosity and fluid saturations. The rock physics model includes the elastic and electrical components and can be applied to the results of seismic and electromagnetic inversion. To describe the non-Gaussian behaviour of the model properties, we adopt non-parametric probability density functions to sample multimodal and skewed distributions of the model variables. Different from machine learning approach, the proposed method is not completely data-driven but is based on a statistical rock physics model to link the model parameters to the data. The proposed method provides pointwise posterior distributions of the porosity and CO2 saturation along with the most-likely models and the associated uncertainty. The method is validated using synthetic and real data acquired for CO2 sequestration studies in different formations: the Rock Springs Uplift in Southwestern Wyoming and the Johansen formation in the North Sea, offshore Norway. The proposed approach is validated under different noise conditions and compared to traditional parametric approaches based on Gaussian assumptions. The results show that the proposed method provides an accurate inversion framework where instead of fitting the relationship between the model and the data, we account for the uncertainty in the rock physics model.

Description: The Be X-ray binary GRO J2058+42 recently went through a Type-II outburst during 2019 March–April lasting for about 50 d. This outburst was detected with the operating all sky X-ray monitors like the Fermi-GBM, Swift-BAT, and MAXI-GSC. Two Nuclear Spectroscopic Telescope Array(NuSTAR) observations were also made, one during the rise and other during the decay of the outburst. It gave us the unique opportunity to analyse the broad-band characteristics of the pulsar for the first time and accretion torque characteristics of the pulsar over a range of X-ray luminosity. The pulse profiles are strongly energy-dependent, with at least four different pulse components at low energy (〈 20 keV), which evolves to a single-peaked profile at high energy (〉 30 keV). In each of the narrow energy bands, the pulse profiles are nearly identical in the two NuSTAR observations. The spectra from both the observations are fitted well to a power-law with a Fermi–Dirac-type high-energy cutoff. We ruled out presence of a cyclotron line in the pulse phase averaged X-ray spectrum in the NuSTAR band with an optical depth greater than 0.15. An iron emission line is detected in both the NuSTAR spectra with an equivalent width of about 125 eV. We looked at the dependence of the spin-up rate on the luminosity and estimated the magnetic field strength from that, which came out to be much higher compared to other known BeXRB pulsars. Lastly, we discussed the inadequacy of the torque–luminosity relation for determination of magnetic field strength of neutron stars.

Description: SUMMARY The horizontal-to-vertical spectral ratio (HVSR) of ambient noise is commonly used to infer a site's resonance frequency (${f_{0,site}}$). HVSR calculations are performed most commonly using the Fourier amplitude spectrum obtained from a single merged horizontal component (e.g. the geometric mean component) from a three-component sensor. However, the use of a single merged horizontal component implicitly relies on the assumptions of azimuthally isotropic seismic noise and 1-D surface and subsurface conditions. These assumptions may not be justified at many sites, leading to azimuthal variability in HVSR measurements that cannot be accounted for using a single merged component. This paper proposes a new statistical method to account for azimuthal variability in the peak frequency of HVSR curves (${f_{0,HVSR}}$). The method uses rotated horizontal components at evenly distributed azimuthal intervals to investigate and quantify azimuthal variability. To ensure unbiased statistics for ${f_{0,HVSR}}$ are obtained, a frequency-domain window-rejection algorithm is applied at each azimuth to automatically remove contaminated time windows in which the ${f_{0,HVSR}}$ values are statistical outliers relative to those obtained from the majority of windows at that azimuth. Then, a weighting scheme is used to account for different numbers of accepted time windows at each azimuth. The new method is applied to a data set of 114 HVSR measurements with significant azimuthal variability in ${f_{0,HVSR}}$, and is shown to reliably account for this variability. The methodology is also extended to the estimation of a complete lognormal-median HVSR curve that accounts for azimuthal variability. To encourage the adoption of this statistical approach to accounting for azimuthal variability in single-station HVSR measurements, the methods presented in this paper have been incorporated into hvsrpy, an open-source Python package for HVSR processing.

Description: We find that the minor axes of the ultra-diffuse galaxies (UDGs) in Abell 2634 tend to be aligned with the major axis of the central dominant galaxy, at a $gtrsim 95{{ m per cent}}$ confidence level. This alignment is produced by the bright UDGs with the absolute magnitudes Mr 〈 −15.3 mag, and outer-region UDGs with R 〉 0.5R200. The alignment signal implies that these bright, outer-region UDGs are very likely to acquire their angular momenta from the vortices around the large-scale filament before they were accreted into A2634, and form their extended stellar bodies outside of the cluster; in this scenario, the orientations of their primordial angular momenta, which are roughly shown by their minor axes on the images, should tend to be parallel to the elongation of the large-scale filament. When these UDGs fell into the unrelaxed cluster A2634 along the filament, they could still preserve their primordial alignment signal before violent relaxation and encounters. These bright, outer-region UDGs in A2634 are very unlikely to be the descendants of the high-surface-brightness dwarf progenitors under tidal interactions with the central dominant galaxy in the cluster environment. Our results indicate that the primordial alignment could be a useful probe of the origin of UDGs in large-scale structures.

Description: The Milky Way is one of the very few spiral galaxies known to host large-scale magnetic field reversals. The existence of the field reversal in the first Galactic quadrant near the Sagittarius spiral arm has been well established, yet poorly characterized due to the insufficient number of reliable Faraday depths (FDs) from extragalactic radio sources (EGSs) through this reversal region. We have therefore performed broad-band (1–$2, { m GHz}$) spectropolarimetric observations with the Karl G. Jansky Very Large Array (VLA) to determine the FD values of 194 EGSs in the Galactic longitude range of 20°–52° within ±5° from the Galactic mid-plane, covering the Sagittarius arm tangent. This factor of five increase in the EGS FD density has led to the discovery of a disparity in FD values across the Galactic mid-plane in the Galactic longitude range of 40°–52°. Combined with existing pulsar FD measurements, we suggest that the Sagittarius arm can host an odd-parity disc field. We further compared our newly derived EGS FDs with the predictions of three major Galactic magnetic field models, and concluded that none of them can adequately reproduce our observational results. This has led to our development of new, improved models of the Milky Way disc magnetic field that will serve as an important step towards major future improvements in Galactic magnetic field models.

Description: We use the astrometric and photometric data from Gaia Data Release 2 and line-of-sight velocities from various other surveys to study the 3D structure and kinematics of the Sagittarius dwarf galaxy. The combination of photometric and astrometric data makes it possible to obtain a very clean separation of Sgr member stars from the Milky Way foreground; our final catalogue contains 2.6 × 105 candidate members with magnitudes G 〈 18, more than half of them being red clump stars. We construct and analyse maps of the mean proper motion and its dispersion over the region ∼30 × 12 deg, which show a number of interesting features. The intrinsic 3D density distribution (orientation, thickness) is strongly constrained by kinematics; we find that the remnant is a prolate structure with the major axis pointing at ∼45° from the orbital velocity and extending up to ∼5 kpc, where it transitions into the stream. We perform a large suite of N-body simulations of a disrupting Sgr galaxy as it orbits the Milky Way over the past 2.5 Gyr, which are tailored to reproduce the observed properties of the remnant (not the stream). The richness of available constraints means that only a narrow range of parameters produce a final state consistent with observations. The total mass of the remnant is $sim !4imes 10^8, mathrm{M}_odot$, of which roughly a quarter resides in stars. The galaxy is significantly out of equilibrium, and even its central density is below the limit required to withstand tidal forces. We conclude that the Sgr galaxy will likely be disrupted over the next Gyr.

Description: SUMMARY This study focuses in the analysis of the internal structure of the upper 3 km of Los Humeros (LH) caldera and the relation of electrical and hydrothermal anomalies. For this purpose, we measured, processed and interpreted 78 broad-band magnetotelluric (MT) soundings. We performed a 3-D inversion of the data set (ModEM) using all MT soundings, although only half of the available frequencies per sounding due to limited computed power. We also carried out the 2-D inversions (NLCG) of the invariant determinant along two orthogonal profiles (EW and NS) crossing the caldera structure; their comparison yields similar resistivity and structural models results. The resistivity modelling is complemented with the results of a joint 3-D inversion of an accurate gravity database of 720 stations, and total field aeromagnetic data (SGM) from the caldera crater. The combined results provide novel details about the structure of the shallow geothermal reservoir of the resurgence caldera complex hosting the active hydrothermal system. Density and resistivity models show the existence of a composed crater basin structure separated by an EW high-density structure; the northern basin is associated to the LH crater, whereas the southern basin associates to the emergent Los Potreros (LP) caldera basin. The magnetization model indicates that there is a common source for the magnetic volcanic products observed at the caldera surface, and that the LP fault is the more magnetized fault of the geothermal system. The propylic zoning under the geothermal field, which according to the MT model results has resistivities above ∼100 Ω-m, was extrapolated using this and additional criteria to obtain the distribution of other hypothetical propylitic zones of hydrothermal potential.

Description: Data Challenge 1 (DC1) is the first synthetic data set produced by the Rubin Observatory Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC). DC1 is designed to develop and validate data reduction and analysis and to study the impact of systematic effects that will affect the LSST data set. DC1 is comprised of r-band observations of 40 deg2 to 10 yr LSST depth. We present each stage of the simulation and analysis process: (a) generation, by synthesizing sources from cosmological N-body simulations in individual sensor-visit images with different observing conditions; (b) reduction using a development version of the LSST Science Pipelines; and (c) matching to the input cosmological catalogue for validation and testing. We verify that testable LSST requirements pass within the fidelity of DC1. We establish a selection procedure that produces a sufficiently clean extragalactic sample for clustering analyses and we discuss residual sample contamination, including contributions from inefficiency in star–galaxy separation and imperfect deblending. We compute the galaxy power spectrum on the simulated field and conclude that: (i) survey properties have an impact of 50 per cent of the statistical uncertainty for the scales and models used in DC1; (ii) a selection to eliminate artefacts in the catalogues is necessary to avoid biases in the measured clustering; and (iii) the presence of bright objects has a significant impact (2σ–6σ) in the estimated power spectra at small scales (ℓ 〉 1200), highlighting the impact of blending in studies at small angular scales in LSST.

Description: The advent of a new generation of large-scale galaxy surveys is pushing cosmological numerical simulations in an uncharted territory. The simultaneous requirements of high resolution and very large volume pose serious technical challenges, due to their computational and data storage demand. In this paper, we present a novel approach dubbed dynamic zoom simulations – or dzs – developed to tackle these issues. Our method is tailored to the production of light-cone outputs from N-body numerical simulations, which allow for a more efficient storage and post-processing compared to standard comoving snapshots, and more directly mimic the format of survey data. In dzs, the resolution of the simulation is dynamically decreased outside the light-cone surface, reducing the computational work load, while simultaneously preserving the accuracy inside the light-cone and the large-scale gravitational field. We show that our approach can achieve virtually identical results to traditional simulations at half of the computational cost for our largest box. We also forecast this speedup to increase up to a factor of 5 for larger and/or higher resolution simulations. We assess the accuracy of the numerical integration by comparing pairs of identical simulations run with and without dzs. Deviations in the light-cone halo mass function, in the sky-projected light-cone, and in the 3D matter light-cone always remain below 0.1 per cent. In summary, our results indicate that the dzs technique may provide a highly valuable tool to address the technical challenges that will characterize the next generation of large-scale cosmological simulations.

Description: Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy density evolving as $widetilde{Omega }_{ m {DE}}(z) = Omega _{ m {DE,0}}[ 1 - { m {tanh}}({log }_{10}(1+z))]$, i.e. with no degree of freedom. Later on, a generalized model was proposed by adding one degree of freedom to the PEDE model, encoded in the parameter Δ. Motivated by these proposals, we constrain the parameter space ($h,Omega _m^{(0)}$) and ($h,Omega _m^{(0)}, Delta$) for PEDE and generalized emergent dark energy (GEDE), respectively, by employing the most recent observational (non-)homogeneous and differential age Hubble data. Additionally, we reconstruct the deceleration and jerk parameters and estimate yield values at z = 0 of $q_0 = -0.784^{+0.028}_{-0.027}$ and $j_0 = 1.241^{+0.164}_{-0.149}$ for PEDE and $q_0 = -0.730^{+0.059}_{-0.067}$ and $j_0 = 1.293^{+0.194}_{-0.187}$ for GEDE using the homogeneous sample. We report values on the deceleration–acceleration transition redshift with those reported in the literature within 2σ CL. Furthermore, we perform a stability analysis of the PEDE and GEDE models to study the global evolution of the Universe around their critical points. Although the PEDE and GEDE dynamics are similar to the standard model, our stability analysis indicates that in both models there is an accelerated phase at early epochs of the Universe evolution.

Description: We present an overview of, and first science results from, the Magellanic Edges Survey (MagES), an ongoing spectroscopic survey mapping the kinematics of red clump and red giant branch stars in the highly substructured periphery of the Magellanic Clouds. In conjunction with Gaia astrometry, MagES yields a sample of ~7000 stars with individual 3D velocities that probes larger galactocentric radii than most previous studies. We outline our target selection, observation strategy, data reduction, and analysis procedures, and present results for two fields in the northern outskirts (〉10° on-sky from the centre) of the Large Magellanic Cloud (LMC). One field, located in the vicinity of an arm-like overdensity, displays apparent signatures of perturbation away from an equilibrium disc model. This includes a large radial velocity dispersion in the LMC disc plane, and an asymmetric line-of-sight velocity distribution indicative of motions vertically out of the disc plane for some stars. The second field reveals 3D kinematics consistent with an equilibrium disc, and yields Vcirc = 87.7 ± 8.0 km s−1 at a radial distance of ~10.5 kpc from the LMC centre. This leads to an enclosed mass estimate for the LMC at this radius of (1.8 ± 0.3) × 1010 M⊙.

Description: We present a novel method of robust probabilistic cosmic web particle classification in three dimensions using a supervised machine learning algorithm. Training data were generated using a simplified ΛCDM toy model with pre-determined algorithms for generating haloes, filaments, and voids. While this framework is not constrained by physical modelling, it can be generated substantially more quickly than an N-body simulation without loss in classification accuracy. For each particle in this data set, measurements were taken of the local density field magnitude and directionality. These measurements were used to train a random forest algorithm, which was used to assign class probabilities to each particle in a ΛCDM, dark matter-only N-body simulation with 2563 particles, as well as on another toy model data set. By comparing the trends in the ROC curves and other statistical metrics of the classes assigned to particles in each data set using different feature sets, we demonstrate that the combination of measurements of the local density field magnitude and directionality enables accurate and consistent classification of halo, filament, and void particles in varied environments. We also show that this combination of training features ensures that the construction of our toy model does not affect classification. The use of a fully supervised algorithm allows greater control over the information deemed important for classification, preventing issues arising from arbitrary hyperparameters and mode collapse in deep learning models. Due to the speed of training data generation, our method is highly scalable, making it particularly suited for classifying large data sets, including observed data.

Description: We investigate observational constraints on cosmological parameters combining 15 measurements of the transversal BAO scale (obtained free of any fiducial cosmology) with Planck–CMB data to explore the parametric space of some cosmological models. We investigate how much Planck + transversal BAO data can constraint the minimum Lambda cold dark matter (ΛCDM) model, and extensions, including neutrinos mass scale Mν, and the possibility for a dynamical dark energy (DE) scenario. Assuming the ΛCDM cosmology, we find H0 = 69.23 ± 0.50 km s−1 Mpc−1, Mν 〈 0.11 eV, and rdrag = 147.59 ± 0.26 Mpc (the sound horizon at drag epoch) from Planck + transversal BAO data. When assuming a dynamical DE cosmology, we find that the inclusion of the BAO data can indeed break the degeneracy of the DE free parameters, improving the constraints on the full parameter space significantly. We note that the model is compatible with local measurements of H0 and there is no tension on H0 estimates in this dynamical DE context. Also, we discuss constraints and consequences from a joint analysis with the local H0 measurement from SH0ES. Finally, we perform a model-independent analysis for the deceleration parameter, q(z), using only information from transversal BAO data.

Description: SUMMARY For the time stationary global geomagnetic field, a new modelling concept is presented. A Bayesian non-parametric approach provides realistic location dependent uncertainty estimates. Modelling related variabilities are dealt with systematically by making little subjective a priori assumptions. Rather than parametrizing the model by Gauss coefficients, a functional analytic approach is applied. The geomagnetic potential is assumed a Gaussian process to describe a distribution over functions. A priori correlations are given by an explicit kernel function with non-informative dipole contribution. A refined modelling strategy is proposed that accommodates non-linearities of archeomagnetic observables: First, a rough field estimate is obtained considering only sites that provide full field vector records. Subsequently, this estimate supports the linearization that incorporates the remaining incomplete records. The comparison of results for the archeomagnetic field over the past 1000 yr is in general agreement with previous models while improved model uncertainty estimates are provided.

Description: The spectral energy distributions of some nearby stars show mid-infrared (IR) excesses from warm habitable zone dust, known as exozodiacal dust. This dust may originate in collisions in a planetesimal belt before being dragged inwards. This paper presents an analytical model for the size distribution of particles at different radial locations in such a scenario, considering evolution due to destructive collisions and Poynting–Robertson (P–R) drag. Results from more accurate but computationally expensive numerical simulations of this process are used to validate the model and fit its free parameters. The model predicts 11 μm excesses (R11) for discs with a range of dust masses and planetesimal belt radii using realistic grain properties. We show that P–R drag should produce exozodiacal dust levels detectable with the Large Binocular Telescope Interferometer (LBTI) ($R_{11} gt 0.1{{ m per cent}}$) in systems with known outer belts; non-detection may indicate dust depletion, e.g. by an intervening planet. We also find that LBTI could detect exozodiacal dust dragged in from a belt too faint to detect at far-IR wavelengths, with fractional luminosity f ∼ 10−7 and radius ∼10–80 au. Application to systems observed with LBTI shows that P–R drag can likely explain most (5/9) of the exozodiacal dust detections in systems with known outer belts; two systems (β Uma and η Corvi) with bright exozodi may be due to exocomets. We suggest that the three systems with exozodiacal dust detections but no known belt may have cold planetesimal belts too faint to be detectable in the far-IR. Even systems without outer belt detections could have exozodiacal dust levels $R_{11} gt 0.04{{ m per cent}}$ which are problematic for exo-Earth imaging.

Description: SUMMARY Rapid development of time-lapse seismic monitoring instrumentations has made it possible to collect dense time-lapse data for tomographically retrieving time-lapse (even continuous) images of subsurface changes. While traditional time-lapse full waveform inversion (TLFWI) algorithms are designed for sparse time-lapse surveys, they lack of effective temporal constraint on time-lapse data, and, more importantly, lack of the uncertainty estimation of the TLFWI results that is critical for further interpretation. Here, we propose a new data assimilation TLFWI method, using hierarchical matrix powered extended Kalman filter (HiEKF) to quantify the image uncertainty. Compared to existing Kalman filter algorithms, HiEKF allows to store and update a data-sparse representation of the cross-covariance matrices and propagate model errors without expensive operations involving covariance matrices. Hence, HiEKF is computationally efficient and applicable to 3-D TLFWI problems. Then, we reformulate TLFWI in the framework of HiEKF (termed hereafter as TLFWI-HiEKF) to predict time-lapse images of subsurface spatiotemporal velocity changes and simultaneously quantify the uncertainty of the inverted velocity changes over time. We demonstrate the validity and applicability of TLFWI–HiEKF with two realistic CO2 monitoring models derived from Frio-II and Cranfield CO2 injection sites, respectively. In both 2-D and 3-D examples, the inverted high-resolution time-lapse velocity results clearly reveal a continuous velocity reduction due to the injection of CO2. Moreover, the accuracy of the model is increasing over time by assimilating more time-lapse data while the standard deviation is decreasing over lapsed time. We expect TLFWI-HiEKF to be equipped with real-time seismic monitoring systems for continuously imaging the distribution of subsurface gas and fluids in the future large-scale CO2 sequestration experiments and reservoir management.

Description: We have measured the Stark widths and shifts of V II spectral lines in the wavelength range 2000–4200 Å belonging to 75 multiplets. The spectra are emitted by laser-induced plasmas generated from fused glass discs prepared by borate fusion. The electron density and temperature are in the ranges (0.72–6.5) × 1017 cm−3 and (11 000–14 900) K, respectively. To avoid self-absorption, we have used seven samples with vanadium concentrations selected by the CSigma graph methodology. This has allowed to include strong and weak lines in the study, including resonance and forbidden lines. The experimental widths and shifts are compared with theoretical values available in the literature.

Description: We report on the detection of extreme giant pulses (GPs) from one of the oldest known pulsars, the highly variable PSR B0950+08, with the Amsterdam-ASTRON Radio Transient Facility And Analysis Centre (AARTFAAC), a parallel transient detection instrument operating as a subsystem of the LOw Frequency ARray (LOFAR). During processing of our Northern Hemisphere survey for low-frequency radio transients, a sample of 275 pulses with fluences ranging from 42 to 177 kJy ms were detected in one-second snapshot images. The brightest pulses are an order of magnitude brighter than those previously reported at 42 and 74 MHz, on par with the levels observed in a previous long-term study at 103 MHz. Both their rate and fluence distribution differ between and within the various studies done to date. The GP rate is highly variable, from 0 to 30 per hour, with only two 3-h observations accounting for nearly half of the pulses detected in the 96 h surveyed. It does not vary significantly within a few-hour observation, but can vary strongly one from day to the next. The spectra appear strongly and variably structured, with emission sometimes confined to a single 195.3 kHz subband, and the pulse spectra changing on a time-scale of order 10 min.

Description: The structured winds of single massive stars can be classified into two broad groups: stochastic structure and organized structure. While the former is typically identified with clumping, the latter is typically associated with rotational modulations, particularly the paradigm of corotating interaction regions (CIRs). While CIRs have been explored extensively in the ultraviolet band, and moderately in the X-ray and optical, here we evaluate radio variability from CIR structures assuming free–free opacity in a dense wind. Our goal is to conduct a broad parameter study to assess the observational feasibility, and to this end, we adopt a phenomenological model for a CIR that threads an otherwise spherical wind. We find that under reasonable assumptions, it is possible to obtain radio variability at the 10 per cent level. The detailed structure of the folded light curve depends not only on the curvature of the CIR, the density contrast of the CIR relative to the wind, and viewing inclination, but also on wavelength. Comparing light curves at different wavelengths, we find that the amplitude can change, that there can be phase shifts in the waveform, and the entire waveform itself can change. These characterstics could be exploited to detect the presence of CIRs in dense, hot winds.

Description: The ion populations most frequently adopted for diagnostics in collisional plasmas are derived from the density independent coronal approximation. In higher density, lower temperature conditions, ionization rates are enhanced once metastable levels become populated, and recombination rates are suppressed if ions recombine into Rydberg levels. As a result, the formation temperatures of ions shift, altering the diagnostics of the plasma. To accurately model the effect of ionization from metastable levels, new electron impact ionization cross-sections have been calculated for oxygen, both for direct ionization and excitation–auto-ionization of the ground and metastable levels. The results have been incorporated into collisional radiative modelling to show how the ionization equilibrium of oxygen changes once metastable levels become populated. Suppression of dielectronic recombination has been estimated and also included in the modelling, demonstrating the shifts with density in comparison to the coronal approximation. The final results for the ionization equilibrium are used in differential emission measure modelling to predict line intensities for many lines emitted by O ii–O vi in the solar transition region. The predictions show improved agreement by 15–40 per cent for O ii, O vi, and the intercombination lines of O iii–O v, when compared to results from coronal approximation modelling. While there are still discrepancies with observations of these lines, this could, to a large part, be explained by variability in the observations.

Description: Using an idealized set-up, we investigate the dynamical role of cosmic rays (CRs) in the early stages of galactic outflows for galaxies of halo masses 108, 1011, and 1012 M⊙. The outflow is launched from a central region in the galactic disc where we consider three different constant star formation rates (0.1, 1, and 10 $mathrm{M}_odot , mathrm{yr}^{-1}$) over a dynamical time-scale of 50 Myr. We determine the temperature distribution of the gas and find that CRs can reduce the temperature of the shocked gas, which is consistent with previous results. However, we show that CRs do not have any noticeable effect on the mass loading by the outflow. We find that CRs can reduce the size of the outflow, which contradicts previous claims of efficient dynamical impact of CRs; however, it is consistent with earlier theoretical models of CR-driven blastwave as well as stellar wind. We discuss the dependence of our results on CR injection prescriptions and compare them with earlier studies. We conclude that in the early stages of galactic outflows the dynamical role of CRs is not important.

Description: We present observations of the H α, H β, [S ii] λλ6716, 6731 and [N ii] λ6583 emission lines in the galactic H ii region Sh2-235 with the Mapper of Narrow Galaxy Lines (MaNGaL), a tunable filter at the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We show that the H ii region is obscured by neutral material with AV ≈ 2−4 mag. The area with the highest AV is situated to the south-west from the ionizing star and coincides with a maximum detected electron density of ≳300 cm−3. The combination of these results with archive AKARI far-infrared data allows us to estimate the contribution of the front and rear walls to the total column density of neutral material in S235 and explain the 3D structure of the region. The H ii region consist of a denser, more compact portion deeply embedded in the neutral medium and the less dense and obscured gas. The front and rear walls of the H ii region are inhomogeneous, with the material in the rear wall having a higher column density. We find a two-sided photodissociation region in the dense clump S235 East 1, illuminated by a UV field with G0 = 50−70 and 200 Habing units in the western and eastern parts, respectively.

Description: CONSERT, a bistatic radar onboard the Rosetta spacecraft and its Philae lander, was designed to probe the nucleus of comet 67P/Churyumov–Gerasimenko with radio waves at 90 MHz frequency. In 2016 September, the exact position of Philae was retrieved, within the region previously identified by CONSERT. This allowed us to revisit the measurements and improve our analysis of the properties of the interior, the results of which we present here. The relative permittivity of the materials is found to range from about 1.7 to 1.95 in the shallow subsurface (

Description: SUMMARY Seven years after the beginning of a massive wastewater injection project in eastern Colombia, local earthquake activity increased significantly. The field operator and the Colombian Geological Survey immediately reinforced the monitoring of the area. Our analysis of the temporal evolution of the seismic and injection data together with our knowledge of the geological parameters of the region indicate that the surge of seismicity is being induced by the re-injection of produced water into the same three producing reservoirs. Earthquake activity began on known faults once disposal rates had reached a threshold of ∼2 × 106 m3 of water per month. The average reservoir pressure had remained constant at 7.6 MPa after several years of production, sustained by a large, active aquifer. Surface injection pressures in the seismically active areas remain below 8.3 MPa, a value large enough to activate some of the faults. Since faults are mapped throughout the region and many do not have seismicity on them, we conclude that the existence of known faults is not the only control on whether earthquakes are generated. Stress conditions of these faults are open to future studies. Earthquakes are primarily found in four clusters, located near faults mapped by the operator. The hypocentres reveal vertical planes with orientations consistent with focal mechanisms of these events. Stress inversion of the focal mechanisms gives a maximum compression in the direction ENE-WSW, which is in agreement with borehole breakout measurements. Since the focal mechanisms of the earthquakes are consistent with the tectonic stress regime, we can conclude that the seismicity is resulting from the activation of critically stressed faults. Slip was progressive and seismic activity reached a peak before declining to few events per month. The decline in seismicity suggests that most of the stress has been relieved on the main faults. The magnitude of a large majority of the recorded earthquakes was lower than 4, as the pore pressure disturbance did not reach the mapped large faults whose activation might have resulted in larger magnitude earthquakes. Our study shows that a good knowledge of the local fault network and conditions of stress is of paramount importance when planning a massive water disposal program. These earthquakes indicate that while faults provide an opportunity to dispose produced water at an economically attractive volume–pressure ratio, the possibility of induced seismicity must also be considered.

Description: We present a technique to fit the stellar components of the Galaxy by comparing Hess Diagrams (HDs) generated from trilegal models to real data. We apply this technique, which we call mwfitting, to photometric data from the first 3 yr of the Dark Energy Survey (DES). After removing regions containing known resolved stellar systems such as globular clusters, dwarf galaxies, nearby galaxies, the Large Magellanic Cloud, and the Sagittarius Stream, our main sample spans a total area of ∼2300 deg2. We further explore a smaller subset (∼1300 deg2) that excludes all regions with known stellar streams and stellar overdensities. Validation tests on synthetic data possessing similar properties to the DES data show that the method is able to recover input parameters with a precision better than 3 per cent. We fit the DES data with an exponential thick disc model and an oblate double power-law halo model. We find that the best-fitting thick disc model has radial and vertical scale heights of 2.67 ± 0.09 kpc and 925 ± 40 pc, respectively. The stellar halo is fit with a broken power-law density profile with an oblateness of 0.75 ± 0.01, an inner index of 1.82 ± 0.08, an outer index of 4.14 ± 0.05, and a break at 18.52 ± 0.27 kpc from the Galactic centre. Several previously discovered stellar overdensities are recovered in the residual stellar density map, showing the reliability of mwfitting in determining the Galactic components. Simulations made with the best-fitting parameters are a promising way to predict Milky Way star counts for surveys such as the LSST and Euclid.

Description: Studying the ultraviolet dust attenuation, as well as its relation to other galaxy parameters such as the stellar mass, plays an important role in multiwavelength research. This work relates the dust attenuation to the stellar mass of star-forming galaxies, and its evolution with redshift. A sample of galaxies with an estimate of the dust attenuation computed from the infrared excess was used. The dust attenuation versus stellar mass data, separated in redshift bins, was modelled by a single parameter linear function, assuming a non-zero constant apparent dust attenuation for low-mass galaxies. But the origin of this effect is still to be determined and several possibilities are explored (actual high dust content, variation of the dust-to-metal ratio, variation of the stars–dust geometry). The best-fitting parameter of this model is then used to study the redshift evolution of the cosmic dust attenuation and is found to be in agreement with results from the literature. This work also gives evidence to a redshift evolution of the dust attenuation–stellar mass relationship, as is suggested by recent works in the highest redshift range.

Description: Recent detections of thermal inversions in the dayside atmospheres of some hot Jupiters are motivating new avenues to understand the interplay between their temperature structures and other atmospheric conditions. In particular, TiO has long been proposed to cause thermal inversions in hot Jupiters, depending on other factors such as stellar irradiation, C/O, and vertical mixing. TiO also has spectral features in the optical and near-infrared that have been detected. However, interpretations of TiO signatures rely on the accuracy of TiO opacity used in the models. The recently reported toto TiO line list provides a new opportunity to investigate these dependences, which is the goal of this work. First, we investigate how the toto line list affects observable transmission and emission spectra of hot Jupiters at low and high resolutions. The improvement in the toto line list compared to a previous line list results in observable differences in the model spectra, particularly in the optical at high resolution. Secondly, we explore the interplay between temperature structure, irradiation, and composition with TiO as the primary source of optical opacity, using 1D self-consistent atmospheric models. Among other trends, we find that the propensity for thermal inversions due to TiO peaks at C/O ∼ 0.9, consistent with recent studies. Using these models, we further assess metrics to quantify thermal inversions due to TiO, compared to frequently used Spitzer photometry, over a range in C/O, irradiation, metallicity, gravity, and stellar type.

Description: To get the best result for seismic imaging using primary reflections, data with densely-spaced sources and receivers are ideally preferred. However, dense acquisition can sometimes be hindered by various obstacles, like platforms or complex topography. Such areas with large data gaps may deter exploration or monitoring, as conventional imaging strategies would either provide poor seismic images or turn out to be very expensive. Surface-related multiples travel along different paths compared to primaries, illuminating a wider subsurface area and hence making them valuable in case of data with large gaps. We propose different strategies of using surface-related multiples to get around the problem of imaging in the case of a large data gap. Conventional least-squares imaging methods that incorporate surface-related multiples do so by re-injecting the measured wavefield in the forward-modelling process, which makes it still sensitive to missing data. We introduce a ‘non-linear’ inversion approach in which the surface multiples are modelled from the original source field. This makes the method less dependent on the receiver geometry, therefore, effectively exploiting the information from surface multiples in cases of limited illumination. However, such an approach is sensitive to the knowledge of the source properties. Therefore, we propose a ‘hybrid’ method that combines the non-linear imaging method with the conventional ‘linear’ multiple imaging method, which further improves our imaging result. We test the methods on numerical as well as field data. The results indicate substantial removal of artefacts in the image derived from linear imaging methods due to incomplete data, by exploiting the surface multiples to a maximum extent.

Description: To study the nature of magnetohydrodynamic (MHD) kink waves, the temporal behaviour of an initial kink perturbation of a typical coronal flux tube has been investigated in this paper. The flux tube has a transitional layer that separates the core region of the tube from the surrounding environment. In the transitional layer, the background density and magnetic field varies continuously from the internal to the external values. The magnetic field is straight and aligned with the tube axis in the internal and external regions of the flux tube, but is assumed to be twisted in the transitional layer. Hence, in the transitional layer the background Alfvén speed is inhomogeneous and perturbations become out of phase due to the process of phase mixing. Our result shows that as the energy of the wave transfers to the local Alfvén waves in the inhomogeneous region, the magnetic tension force becomes the dominant restoring force of the wave. The numerical results show that the nature of the small-scale oscillations in the transitional layer is determined by the ratio of the azimuthal components of the restoring forces.

Description: We constrain and update the bounds on the lifetime of a decaying dark matter model with a warm massive daughter particle using the most recent low-redshift probes. We use Supernovae Type-Ia, Baryon Acoustic Oscillations and the time delay measurements of gravitationally lensed quasars. These data sets are complemented by the early universe priors taken from the Cosmic Microwave background. For the maximum allowed fraction of the relativistic daughter particle, the updated bounds on the lifetime are found to be $au gt 9, m {Gyr}$ and $au gt 11, m {Gyr}$ at $95{{ m per cent}}$ C.L., for the two-body and many-body decay scenarios, respectively. We also comment on the recent proposal that the current two-body decaying dark matter model can provide resolution for the H0-tension, by contrasting against the standard ΛCDM model. We infer that the current dark matter decaying scenario is unlikely to alleviate the H0-tension. We find that the decaying dark matter is able to reduce the trend of the decreasing H0 values with increasing lens redshifts observed in the strong lensing data set.

Description: The relative abundance of cyanide and isocyanide molecules is a sensitive tracer of the physical conditions in the interstellar and circumstellar media. Accurate modelling of collisional and radiative processes implying these species opens the way for accurate estimation of their abundances. The present paper focuses on the computation of collisional rate coefficients for fine and hyperfine (de-)excitation of the CCN molecule (one of the C2N isomers) in collision with He, for temperatures up to 150 K. Using a time independent coupled-channel approach, scattering calculations were performed for transitions implying the lowest 56 fine structure levels and the corresponding 166 hyperfine structure levels belonging to both 2Π1/2 and 2Π3/2 spin-orbit manifolds. We provided, for the first time, realistic collisional data for the CCN radical. Propensity rules for fine and hyperfine transitions are discussed. As a first application, we evaluated the impact of these new data on the astrophysical modelling through radiative transfer calculations. We obtained the brightness and excitation temperatures of selected lines observed towards circumstellar envelopes and we found that local thermodynamic equilibrium conditions are not fulfilled for this species. As a consequence, our results indicate that the abundance of the CCN derived from the observations has to be revised since the observation modelling strongly depends on the collisional data used.

Description: It has been claimed that the standard model of cosmology (ΛCDM) cannot easily account for a number of observations on relatively small scales, motivating extensions to the standard model. Here, we introduce a new suite of cosmological simulations that systematically explores three plausible extensions: warm dark matter, self-interacting dark matter, and a running of the scalar spectral index of density fluctuations. Current observational constraints are used to specify the additional parameters that come with these extensions. We examine a large range of observable metrics on small scales, including the halo mass function, density, and circular velocity profiles, the abundance of satellite subhaloes, and halo concentrations. For any given metric, significant degeneracies can be present between the extensions. In detail, however, the different extensions have quantitatively distinct mass and radial dependencies, suggesting that a multiprobe approach over a range of scales can be used to break the degeneracies. We also demonstrate that the relative effects on the radial density profiles in the different extensions (compared to the standard model) are converged down to significantly smaller radii than are the absolute profiles. We compare the derived cosmological trends with the impact of baryonic physics using the EAGLE and ARTEMIS simulations. Significant degeneracies are also present between baryonic physics and cosmological variations (with both having similar magnitude effects on some observables). Given the inherent uncertainties both in the modelling of galaxy formation physics and extensions to ΛCDM, a systematic and simultaneous exploration of both is strongly warranted.

Description: The Gaia space mission is crafting revolutionary astrometric, photometric, and spectroscopic catalogues that will allow us to map our Galaxy, but only if we know the completeness of this Gaia-verse of catalogues: what stars does it contain and what stars is it missing? We argue that the completeness is driven by Gaia’s spinning-and-precessing scanning law and will apply this principle to the Gaia-verse over this series. We take a first step by identifying the periods in time that did not contribute any measurements to Gaia DR2; these gaps create ribbons of incompleteness across the sky that will bias any study that ignores them, although some of these gaps may be filled in future data releases. Our first approach was to use the variable star photometry to identify the 94 gaps longer than 1 per cent of a day. Our second approach was to predict the number of observations of every point on the sky, which in comparison to the reported number of detections revealed additional gaps in the astrometry and spectroscopy. Making these predictions required us to make the most precise, publicly available determination of the Gaia scanning law. Using this scanning law, we further identified that most stars fainter than G = 22 in DR2 have spurious magnitudes due to a miscalibration resulting from a thunderstorm over Madrid. Our list of gaps and precision scanning law will allow astronomers to know when Gaia’s eye was truly on their binary star, exoplanet, or microlensing event during the time period of the second data release.

Description: We present a detailed analysis of the gaseous component of the Si K edge using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the spectra with a modified version of the ISMabs model, including new photoabsorption cross-sections computed for all Si ionic species. We estimate column densities for Si i, Si ii, Si iii, Si xii, and Si xiii, which trace the warm, intermediate temperature, and hot phases of the Galactic interstellar medium. We find that the ionic fractions of the first two phases are similar. This may be due to the physical state of the plasma determined by the temperature or due to the presence of absorber material in the close vicinity of the sources. Our findings highlight the need for accurate modelling of the gaseous component before attempting to address the solid component.

Description: The 2175 Å ultraviolet (UV) extinction bump in interstellar medium (ISM) of the Milky Way was discovered in 1965. After intensive exploration of more than a half century, however, its exact origin still remains a big conundrum that is being debated. Here, we propose a mixture model by which the extinction bump in ISM is argued possibly relevant to the clusters of hydrogenated T-carbon (HTC) molecules (C40H16) that have intrinsically a sharp absorption peak at the wavelength 2175 Å. By linearly combining the calculated absorption spectra of HTC mixtures, graphite, MgSiO3, and Fe2SiO4, we show that the UV extinction curves of optional six stars can be nicely fitted. This work poses an alternative explanation towards understanding the physical origin of the 2175 Å extinction bump in ISM of the Milky Way.

Description: Due to differing gravitational potentials and path lengths, gravitational lensing induces time delays between multiple images of a source that, for solar mass objects, are of the order of ∼10−5 s. If an astrophysically compact source, such as a fast radio burst (FRB), is observed through a region with a high optical depth of such microlensing masses, this gravitational lensing time delay can be imprinted on short time-scale transient signals. In this paper, we consider the impact of the parity of the macroimage on the resultant microlensing time delays. It is found that this parity is directly imprinted on the microlensing signal, with macroimages formed at minima of the time arrival surface beginning with the most highly magnified microimages and then progressing to the fainter microimages. For macroimages at the maxima of the time arrival surface, this situation is reversed, with fainter images observed first and finishing with the brightest microimages. For macroimages at saddle points, the signal again begins with fainter images, followed by brighter images before again fading through the fainter microimages. The growing populations of cosmologically distant bursty transient sources will undoubtedly result in the discovery of strong lensed, multiply imaged FRBs, which will be susceptible to microlensing by compact masses. With the temporal resolution being offered by modern and future facilities, the detection of microlensing-induced time delays will reveal the parities of the gravitational lens macroimages, providing additional constraints on macrolensing mass models and improving the efficacy of these transient sources as cosmological probes.

Description: Mixing of 56Ni, whose nuclear decay energy is a major luminosity source in stripped-envelope supernovae, is known to affect the observational properties of stripped-envelope supernovae such as light-curve and colour evolution. Here we systematically investigate the effect of 56Ni mixing on the photospheric velocity evolution in stripped-envelope supernovae. We show that 56Ni mixing significantly affects the early photospheric velocity evolution. The photospheric velocity, which is often used to constrain the ejecta mass and explosion energy, significantly varies by just changing the degree of 56Ni mixing. In addition, the models with a small degree of 56Ni mixing show a flattening in the early photospheric velocity evolution, while the fully mixed models show a monotonic decrease. The velocity flattening appears in both helium and carbon+oxygen progenitor explosions with a variety of ejecta mass, explosion energy, and 56Ni mass. Some stripped-envelope supernovae with early photospheric velocity information do show such a flattening. We find that Type Ib SN 2007Y, which has early photospheric velocity information, has a signature of a moderate degree of 56Ni mixing in the photospheric velocity evolution and about half of the ejecta is mixed in it. The immediate spectroscopic follow-up observations of stripped-envelope supernovae shortly after the explosion providing the early photospheric evolution give an important clue to constrain 56Ni mixing in the ejecta.

Description: We study star cluster formation in various environments with different metallicities and column densities by performing a suite of 3D radiation hydrodynamics simulations. We find that the photoionization feedback from massive stars controls the star formation efficiency (SFE) in a star-forming cloud, and its impact sensitively depends on the gas metallicity Z and initial cloud surface density Σ. At Z = 1 Z⊙, SFE increases as a power law from 0.03 at Σ = 10 M⊙ pc−2 to 0.3 at $Sigma = 300,mathrm{M}_{odot }, { m pc^{-2}}$. In low-metallicity cases $10^{-2}!-!10^{-1}, mathrm{Z}_{odot }$, star clusters form from atomic warm gases because the molecule formation time is not short enough with respect to the cooling or dynamical time. In addition, the whole cloud is disrupted more easily by expanding H ii bubbles that have higher temperature owing to less efficient cooling. With smaller dust attenuation, the ionizing radiation feedback from nearby massive stars is stronger and terminate star formation in dense clumps. These effects result in inefficient star formation in low-metallicity environments: the SFE drops by a factor of ∼3 at Z = 10−2 Z⊙ compared to the results for Z = 1 Z⊙, regardless of Σ. Newborn star clusters are also gravitationally less bound. We further develop a new semi-analytical model that can reproduce the simulation results well, particularly the observed dependencies of the SFEs on the cloud surface densities and metallicities.

Description: We report the detection of phase-locked polarization in the bright (mV = 2.98−3.24) semidetached eclipsing binary μ1 Sco (HD 151890). The phenomenon was observed in multiple photometric bands using two different HIPPI-class (HIgh Precision Polarimetric Instrument) polarimeters with telescopes ranging in size from 35 cm to 3.9 m. The peak-to-trough amplitude of the polarization is wavelength dependent and large, ∼700 ppm in green light, and is easily seen with even the smallest telescope. We fit the polarization phase curve with a synspec/vlidort polarized radiative transfer model and a Wilson–Devinney geometric formalism, which we describe in detail. Light from each star reflected by the photosphere of the other, together with a much smaller contribution from tidal distortion and eclipse effects, wholly accounts for the polarization amplitude. In the past, polarization in semidetached binaries has been attributed mostly to scattering from extra-stellar gas. Our new interpretation facilitates determining masses of such stars in non-eclipsing systems.

Description: Low-ionization broad absorption line quasars (LoBALs) mark an important, yet poorly understood, population of quasars showing direct evidence for energetic mass outflows. We outline a sample of 12 luminous (Lbol 〉 1046 ergs−1) LoBALs at 2.0 〈 z 〈 2.5 – a key epoch in both star formation and black hole accretion, which have been imaged as part of a targeted program with the Herschel Spectral and Photometric Imaging REceiver (SPIRE). We present K-band NOTCam spectra for three of these targets, calculating their spectroscopic redshifts, black hole masses, and bolometric luminosities, and increasing the total number of LoBAL targets in our sample with spectral information from five to eight. Based on FIR observations from Herschel SPIRE, we derive prolific star formation rates (SFRs) ranging 740–2380 M⊙ yr−1 for the detected targets, consistent with LoBALs existing in an evolutionary phase associated with starburst activity. Furthermore, an upper limit of

Description: We study whether polycyclic aromatic hydrocarbons (PAHs) can be a weighty source of small hydrocarbons in photodissociation regions (PDRs). We modelled the evolution of 20 specific PAH molecules in terms of dehydrogenation and destruction of the carbon skeleton under the physical conditions of two well-studied PDRs, the Orion Bar, and the Horsehead nebula that represent prototypical examples of PDRs irradiated by ‘high’ and ‘low’ ultraviolet radiation field. PAHs are described as microcanonical systems. The acetylene molecule is considered as the main carbonaceous fragment of the PAH dissociation, as it follows from laboratory experiments and theory. We estimated the rates of acetylene production in gas phase chemical reactions and compared them with the rates of the acetylene production through the PAH dissociation. It is found that the latter rates can be higher than the former rates in the Orion Bar at AV 〈 1 and also at AV 〉 3.5. In the Horsehead nebula, the chemical reactions provide more acetylene than the PAH dissociation. The produced acetylene participate in the reactions of the formation of small hydrocarbons (C2H, C3H, C3H+, C3H2, C4H). Acetylene production via the PAH destruction may increase the abundances of small hydrocarbons produced in gas phase chemical reactions in the Orion Bar only at AV 〉 3.5. In the Horsehead nebula, the contribution of PAHs to the abundances of the small hydrocarbons is negligible. We conclude that the PAHs are not a major source of small hydrocarbons in both PDRs except some locations in the Orion Bar.

Description: The high-fidelity modelling of optical turbulence is critical to the design and operation of a new class of emerging highly sophisticated astronomical telescopes and adaptive optics instrumentation. In this study, we perform retrospective simulations of optical turbulence over the Hawaiian islands using a mesoscale model. The simulated results are validated against thermosonde data. We focus on turbulence in the free atmosphere, above the atmospheric boundary layer. The free atmosphere is particularly important for adaptive optics performance and for sky coverage calculations and hence has significant impact on performance optimization and scheduling of observations. We demonstrate that a vertical grid spacing of 100 m or finer is needed to faithfully capture the intrinsic variabilities of observed clear air turbulence. This is a particularly timely study because the next generation of extremely large telescopes are currently under construction and their associated suite of instruments are in the design phase. Knowledge of the expected accuracy of optical turbulence simulations and real-time forecasts will enable the design teams to (i) test and develop instrument designs and (ii) formulate operational procedure.

Description: We present an overview of the sample of Northern hemisphere white dwarfs within 40 pc of the Sun detected from Gaia Data Release 2 (DR2). We find that 521 sources are spectroscopically confirmed degenerate stars, 111 of which were first identified as white dwarf candidates from Gaia DR2 and followed up recently with the William Herschel Telescope and Gran Telescopio Canarias. Three additional white dwarf candidates remain spectroscopically unobserved and six unresolved binaries are known to include a white dwarf but were not in our initial selection in the Gaia DR2 Hertzsprung–Russell diagram. Atmospheric parameters are calculated from Gaia and Pan-STARRS photometry for all objects in the sample, confirming most of the trends previously observed in the much smaller 20 pc sample. Local white dwarfs are overwhelmingly consistent with Galactic disc kinematics, with only four halo candidates. We find that DAZ white dwarfs are significantly less massive than the overall DA population ($overline{M}_mathrm{DAZ} =$ 0.59 M⊙, $overline{M}_mathrm{DA} =$ 0.66 M⊙). It may suggest that planet formation is less efficient at higher mass stars, producing more massive white dwarfs. We detect a sequence of crystallized white dwarfs in the mass range from 0.6 $lesssim M/mbox{$mathrm{M}_odot $} lesssim$ 1.0 and find that the vast majority of objects on the sequence have standard kinematic properties that correspond to the average of the sample, suggesting that their nature can be explained by crystallization alone. We also detect 26 double degenerates and white dwarf components in 56 wide binary systems.

Description: We present an analysis of the evolution of the Lyman-series forest into the epoch of reionization using cosmological radiative transfer simulations in a scenario where reionization ends late. We explore models with different mid-points of reionization and gas temperatures. We find that once the simulations have been calibrated to match the mean flux of the observed Lyman-α (Ly α) forest at 4 〈 z 〈 6, they also naturally reproduce the distribution of effective optical depths of the Lyman-β (Ly β) forest in this redshift range. We note that the tail of the largest optical depths that is most challenging to match corresponds to the long absorption trough of ULAS J0148+0600, which we have previously shown to be rare in our simulations. We consider the evolution of the Lyman-series forest out to higher redshifts, and show that future observations of the Ly β forest at z 〉 6 will discriminate between different reionization histories. The evolution of the Ly α and Ly γ forests are less promising as a tool for pushing studies of reionization to higher redshifts due to the stronger saturation and foreground contamination, respectively.

Description: CerealsDB (www.cerealsdb.uk.net) is an online repository of mainly hexaploid wheat (Triticum aestivum) single nucleotide polymorphisms (SNPs) and genotyping data. The CerealsDB website has been designed to enable wheat breeders and scientists to select the appropriate markers for research breeding tasks, such as marker-assisted selection. We report a large update of genotyping information for over 6000 wheat accessions and describe new webtools for exploring and visualizing the data. We also describe a new database of quantitative trait loci that links phenotypic traits to CerealsDB SNP markers and allelic scores for each of those markers. CerealsDB is an open-access website that hosts information on wheat SNPs considered useful for both plant breeders and research scientists. The latest CerealsDB database is available at https://www.cerealsdb.uk.net/cerealgenomics/CerealsDB/indexNEW.php.

Description: This paper uses a dataset from Tanzania with information on consumption, income, and income shocks within and across family networks. Crucially and uniquely, it also contains data on the degree of information existing between each pair of households within family networks. We use these data to construct a novel measure of the quality of information both at the level of household pairs and at the level of the network. We also note that the individual level measures can be interpreted as measures of network centrality. We study risk sharing within these networks and explore whether the rejection of perfect risk sharing that we observe can be related to our measures of information quality. We show that households within family networks with better information are less vulnerable to idiosyncratic shocks. Furthermore, we show that more central households within networks are less vulnerable to idiosyncratic shocks. These results have important implications for the characterisation of the empirical failure of the perfect risk-sharing hypothesis and point to the importance of information frictions.

Description: We show that correlations between the phases of the galaxy density field in redshift space provide additional information about the growth rate of large-scale structure that is complementary to the power-spectrum multipoles. In particular, we consider the multipoles of the line correlation function (LCF), which correlates phases between three collinear points, and use the Fisher forecasting method to show that the LCF multipoles can break the degeneracy between the measurement of the growth rate of structure f and the amplitude of perturbations σ8 that is present in the power-spectrum multipoles at large scales. This leads to an improvement in the measurement of f and σ8 by up to 220 per cent for $k_{ m max} = 0.15 , h, mathrm{Mpc}^{-1}$ and up to 50 per cent for $k_{ m max} = 0.30 , h, mathrm{Mpc}^{-1}$ at redshift z = 0.25, with respect to power-spectrum measurements alone for the upcoming generation of galaxy surveys like DESI and Euclid. The average improvements in the constraints on f and σ8 for $k_{ m max} = 0.15 , h, mathrm{Mpc}^{-1}$ are ∼90 per cent for the DESI BGS sample with mean redshift $overline{z}=0.25$, ∼40 per cent for the DESI ELG sample with $overline{z}=1.25$, and ∼40 per cent for the Euclid Hα galaxies with $overline{z}=1.3$. For $k_{ m max} = 0.30 , h, mathrm{Mpc}^{-1}$, the average improvements are ∼40 per cent for the DESI BGS sample and ∼20 per cent for both the DESI ELG and Euclid Hα galaxies.

Description: The Lu–Hf isotope system and Sr–Nd–Hf–Os isotope systematics of mantle rocks are capable of unravelling the early processes in collision belts, especially in a hot subduction context where the Sm–Nd and U–Pb systems in crustal rocks are prone to resetting owing to high temperatures and interaction with melts during exhumation. To improve models of the Devonian–Carboniferous evolution of the Bohemian Massif, we investigated in detail mafic and ultramafic rocks (eclogite, pyroxenite, and peridotite) from the ultrahigh-pressure and ultrahigh-temperature Kutná Hora Crystalline Complex (KHCC: Úhrov, Bečváry, Doubrava, and Spačice localities). Petrography, multiphase solid inclusions, major and trace element compositions of rocks and minerals, and radiogenic isotopic data document contrasting sources and protoliths as well as effects of subduction-related processes for these rocks. The Úhrov peridotite has a depleted composition corresponding to the suboceanic asthenospheric mantle, whereas Bečváry and Doubrava peridotites represent lithospheric mantle that underwent melt refertilization by basaltic and SiO2-undersaturated melts, respectively. Multiphase solid inclusions enclosed in garnet from Úhrov and Bečváry peridotites represent trapped H2O ± CO2-bearing metasomatizing agents and Fe–Ti-rich melts. The KHCC eclogites either formed by high-pressure crystal accumulation from mantle-derived basaltic melts (Úhrov) or represent a fragment of mid-ocean ridge basalt-like gabbroic cumulate (Spačice) and crustal-derived material (Doubrava) both metamorphosed at high P–T conditions. The Lu–Hf age of 395 ± 23 Ma obtained for the Úhrov peridotite reflects garnet growth related to burial of the asthenospheric mantle during subduction of the oceanic slab. By contrast, Spačice and Doubrava eclogites yield younger Lu–Hf ages of ∼350 and 330 Ma, respectively, representing mixed ages as demonstrated by the strong granulite-facies overprint and trace element zoning in garnet grains. We propose a refined model for the Early Variscan evolution of the Bohemian Massif starting with the subduction of the oceanic crust (Saxothuringian ocean) and associated oceanic asthenospheric mantle (Úhrov) beneath the Teplá–Barrandian at ≥380 Ma, which was responsible for melt refertilization of the associated mantle wedge (Bečváry, Doubrava). This was followed by continental subduction (∼370–360 Ma?) accompanied by the oceanic slab break-off and incorporation of the upwelling asthenospheric mantle into the Moldanubian lithospheric mantle and subsequent coeval exhumation of mantle and crustal rocks at ∼350–330 Ma.

Description: Recently, many gravitational wave events from compact binary mergers have been detected by LIGO. Determining the final mass and spin of the remnant black holes (RBHs) is a fundamental issue and is also important in astrophysics. In this paper, unified models for predicting the final mass and spin of the RBHs from compact binary mergers is proposed. The models achieve a good accuracy within the parameter range of interest. In addition, the rotational energy of the RBHs is also studied that relevant to the electromagnetic counterparts of the mergers. It is found the distribution of the rotational energy of the RBHs from different types of mergers of compact binary has its own characteristics, which might help identify the electromagnetic counterparts associated with the mergers.

Description: We present detailed spectroscopic analysis of the extraordinarily fast-evolving transient AT2018kzr. The transient’s observed light curve showed a rapid decline rate, comparable to the kilonova AT2017gfo. We calculate a self-consistent sequence of radiative transfer models (using tardis) and determine that the ejecta material is dominated by intermediate-mass elements (O, Mg, and Si), with a photospheric velocity of ∼12 000–14 500 $ m {km}, s^{-1}$. The early spectra have the unusual combination of being blue but dominated by strong Fe ii and Fe iii absorption features. We show that this combination is only possible with a high Fe content (3.5 per cent). This implies a high Fe/(Ni+Co) ratio. Given the short time from the transient’s proposed explosion epoch, the Fe cannot be 56Fe resulting from the decay of radioactive 56Ni synthesized in the explosion. Instead, we propose that this is stable 54Fe, and that the transient is unusually rich in this isotope. We further identify an additional, high-velocity component of ejecta material at ∼20 000–26 000 $ m {km}, s^{-1}$, which is mildly asymmetric and detectable through the Ca ii near-infrared triplet. We discuss our findings with reference to a range of plausible progenitor systems and compare with published theoretical work. We conclude that AT2018kzr is most likely the result of a merger between an ONe white dwarf and a neutron star or black hole. As such, it would be the second plausible candidate with a good spectral sequence for the electromagnetic counterpart of a compact binary merger, after AT2017gfo.

Description: We present the analysis of 4 h of spectroscopic observations of NGC 6946 with the SITELLE Imaging Fourier Transform Spectrometer on the Canada–France–Hawaii Telescope, acquired to search for supernova light echoes from its 10 modern supernovae. We develop a novel spectroscopic search method: identifying negatively sloped continua in the narrow-band SN3 filter as candidate highly broadened P-Cygni profiles in the H α line, which would be characteristic of the spectra of supernova ejecta. We test our methodology by looking for light echoes from any of the 10 supernovae observed in NGC 6946 in the past 100 yr. We find no evidence of light echoes above the survey surface brightness limit of 1 × 10−15 erg s−1 cm−2arcsec−2.

Description: The space-borne missions CoRoT and Kepler have revealed numerous mixed modes in red giant stars. These modes carry a wealth of information about red giant cores, but are of limited use when constraining rapid structural variations in their envelopes. This limitation can be circumvented if we have access to the frequencies of the pure acoustic dipolar modes in red giants, i.e. the dipole modes that would exist in the absence of coupling between gravity and acoustic waves. We present a pilot study aimed at evaluating the implications of using these pure acoustic mode frequencies in seismic studies of the helium structural variation in red giants. The study is based on artificial seismic data for a red giant branch stellar model, bracketing seven acoustic dipole radial orders around νmax. The pure acoustic dipole-mode frequencies are derived from a fit to the mixed-mode period spacings and then used to compute the pure acoustic dipole-mode second differences. The pure acoustic dipole-mode second differences inferred through this procedure follow the same oscillatory function as the radial-mode second differences. The additional constraints brought by the dipolar modes allow us to adopt a more complete description of the glitch signature when performing the fit to the second differences. The amplitude of the glitch retrieved from this fit is 15${{ m per cent}}$ smaller than that from the fit based on the radial modes alone. Also, we find that thanks to the additional constraints, a bias in the inferred glitch location, found when adopting the simpler description of the glitch, is avoided.

Description: IGR J17091–3624 is a low-mass X-ray binary (LMXB), which received wide attention from the community thanks to its similarities with the bright black hole system GRS 1915+105. Both systems exhibit a wide range of highly structured X-ray variability during outburst, with time-scales from few seconds to tens of minutes, which make them unique in the study of mass accretion in LMXBs. In this work, we present a general overview into the long-term evolution of IGR J17091–3624, using Swift/XRT observations from the onset of the 2011–2013 outburst in 2011 February till the end of the last bright outburst in 2016 November. We found four re-flares during the decay of the 2011 outburst, but no similar re-flares appear to be present in the latter one. We studied, in detail, the period with the lowest flux observed in the last 10 yr, just at the tail end of the 2011–2013 outburst, using Chandra and XMM-Newton observations. We observed changes in flux as high as a factor of 10 during this period of relative quiescence, without strong evidence of softening in the spectra. This result suggests that the source has not been observed at its true quiescence so far. By comparing the spectral properties at low luminosities of IGR J17091–3624 and those observed for a well-studied population of LMXBs, we concluded that IGR J17091–3624 is most likely to host a black hole as a compact companion rather than a neutron star.

Description: The cyclotron line feature in the X-ray spectrum of the accretion-powered pulsar Her X-1 has been observed and monitored for over three decades. The line energy exhibited a slow secular decline over the period 1995–2014, with a possible (not confirmed) indication of a reversal thereafter. Recent works have shown that the temporal evolution of the line energy may be modelled as a flattening after an earlier decrease until MJD 55400 (±200). In this work, we present the results of AstroSat observations in the context of earlier data and offer a common interpretation through a detailed study of temporal and flux dependence. We find that the variation of the line energy does not support an upward trend but is consistent with the reported flattening after an earlier decrease until MJD $54487^{+515}_{-469}$.

Description: We report time-resolved, high-resolution optical spectropolarimetric observations of the young double-lined spectroscopic binary V1878 Ori. Our observations were collected with the ESPaDOnS spectropolarimeter at the Canada–France–Hawaii Telescope through the BinaMIcS large programme. V1878 Ori A and B are partially convective intermediate mass weak-line T Tauri stars on an eccentric and asynchronous orbit. We also acquired X-ray observations at periastron and outside periastron. Using the least-squares deconvolution technique (LSD) to combine information from many spectral lines, we clearly detected circular polarization signals in both components throughout the orbit. We refined the orbital solution for the system and obtained disentangled spectra for the primary and secondary components. The disentangled spectra were then employed to determine atmospheric parameters of the two components using spectrum synthesis. Applying our Zeeman Doppler imaging code to composite Stokes IV LSD profiles, we reconstructed brightness maps and the global magnetic field topologies of the two components. We find that V1878 Ori A and B have strikingly different global magnetic field topologies and mean field strengths. The global magnetic field of the primary is predominantly poloidal and non-axisymmetric (with a mean field strength of 180 G). While the secondary has a mostly toroidal and axisymmetric global field (mean strength of 310 G). These findings confirm that stars with very similar parameters can exhibit radically different global magnetic field characteristics. The analysis of the X-ray data shows no sign of enhanced activity at periastron, suggesting the lack of strong magnetospheric interaction at this epoch.

Description: We present new spectra obtained using Keck/KCWI and perform kinematics and stellar population analyses of the shell galaxy NGC 474, from both the galaxy centre and a region from the outer shell. We show that both regions have similarly extended star formation histories although with different stellar population properties. The central region of NGC 474 is dominated by intermediate-aged stars (8.3 ± 0.3 Gyr) with subsolar metallicity ([Z/H] = −0.24 ± 0.07 dex) while the observed shell region, which hosts a substantial population of younger stars, has a mean luminosity-weighted age of 4.0 ± 0.5 Gyr with solar metallicities ([Z/H] = −0.03 ± 0.09 dex). Our results are consistent with a scenario in which NGC 474 experienced a major to intermediate merger with a log$(M_*/ m M_odot) sim 10$ mass satellite galaxy at least ${sim}2$ Gyr ago which produced its shell system. This work shows that the direct spectroscopic study of low-surface brightness stellar features, such as shells, is now feasible and opens up a new window to understanding galaxy formation and evolution.