ALBERT

Description: In previous, very deep, optical images of NGC 7293, both a feature that has the morphology of a bow-shock and one with that of a jet, were discovered in the faint 40 arcmin diameter halo of the nebula. Spatially resolved longslit profiles of the Hα and [N ii ] 6548, 6584 Å nebular emission lines from both features have now been obtained. The bow-shaped feature has been found to have Hα radial velocities close to the systemic heliocentric radial velocity, –27 km s –1 , of NGC 7293 and is faint in the [N ii ] 6548, 6584 Å emission lines. Furthermore, the full width of these profiles matches the relative motion of NGC 7293 with its ambient interstellar medium consequently it is deduced that the feature is a real bow-shock caused by the motion of NGC 7293 as it ploughs through this medium. The proper motion of the central star also points towards this halo feature which substantiates this interpretation of its origin. Similarly [N ii ] 6584 Å line profiles reveal that the jet-like filament is indeed a collimated outflow, as suggested by its morphology, at around 300 km s –1 with turbulent widths of around 50 km s –1 . Its low Hα/[N ii ] 6548, 6584 Å brightness ratio suggests collisional ionization as expected in a high-speed jet.

Description: We present 3D hydrodynamical simulations of an isotropic fast wind interacting with a previously ejected toroidally shaped slow wind in order to model both the observed morphology and the kinematics of the planetary nebula (PN) NGC 6302. This source, also known as the Butterfly nebula, presents one of the most complex morphologies ever observed in PNe. From our numerical simulations, we have obtained an intensity map for the Hα emission to make a comparison with the Hubble Space Telescope ( HST ) observations of this object. We have also carried out a proper motion (PM) study from our numerical results, in order to compare with previous observational studies. We have found that the two interacting stellar wind model reproduce well the morphology of NGC 6302, and while the PMs in the models are similar to the observations, our results suggest that an acceleration mechanism is needed to explain the Hubble-type expansion found in HST observations.

Description: In this Letter, we explore the hypothesis that the smooth appearance of bow shocks around some red supergiants (RSGs) might be caused by the ionization of their winds by external sources of radiation. Our numerical simulations of the bow shock generated by IRC –10414 (the first-ever RSG with an optically detected bow shock) show that the ionization of the wind results in its acceleration by a factor of 2, which reduces the difference between the wind and space velocities of the star and makes the contact discontinuity of the bow shock stable for a range of stellar space velocities and mass-loss rates. Our best-fitting model reproduces the overall shape and surface brightness of the observed bow shock and suggests that the space velocity and mass-loss rate of IRC –10414 are 50 km s –1 and 10 –6 M yr –1 , respectively, and that the number density of the local interstellar medium is 3 cm –3 . It also shows that the bow shock emission comes mainly from the shocked stellar wind. This naturally explains the enhanced nitrogen abundance in the line-emitting material, derived from the spectroscopy of the bow shock. We found that photoionized bow shocks are 15–50 times brighter in optical line emission than their neutral counterparts, from which we conclude that the bow shock of IRC –10414 must be photoionized.

Description: We present simultaneous observations of H 2 O maser emission and radio continuum at 1.3 cm carried out with the Australia Telescope Compact Array towards two sources, IRAS 16333–4807 and IRAS 12405–6219, catalogued as planetary nebula (PN) candidates, and where single-dish detections of H 2 O masers have been previously reported. Our goal was to unambiguously confirm the spatial association of the H 2 O masers with these two PN candidates. We detected and mapped H 2 O maser emission in both fields, but only in IRAS 16333–4807 the maser emission is spatially associated with the radio continuum emission. The properties of IRAS 16333–4807 provide strong support for the PN nature of the object, hereby confirming it as the fifth known case of an H 2 O maser-emitting PN. This source is bipolar, like the other four known H 2 O maser-emitting PNe, indicating that these sources might pertain to a usual, but short phase in the evolution of bipolar PNe. In IRAS 12405–6219, the H 2 O maser and radio continuum emission are not associated with each other and, in addition, the available data indicate that this source is an H  ii region rather than a PN.

Description: LoTr 1 is a planetary nebula thought to contain an intermediate-period binary central star system (that is, a system with an orbital period, P , between 100 and, say, 1500 d). The system shows the signature of a K type, rapidly rotating giant and most likely constitutes an accretion-induced post-mass-transfer system similar to other PNe, such as LoTr 5, WeBo 1 and A70. Such systems represent rare opportunities to further the investigation into the formation of barium stars and intermediate-period post-asymptotic giant branch systems – a formation process still far from being understood. Here, we present the first detailed analyses of both the central star system and the surrounding nebula of LoTr 1 using a combination of spectra obtained with Very Large Telescope-Focal Reducer and low dispersion Spectrograph, Anglo-Australian Telescope-UCL Coudé Echelle Spectrograph and New Technology Telescope-European Southern Observatory Multi-Mode Instrument, as well as SuperWASP (Wide Angle Search for Planets) photometry. We confirm the binary nature of the central star of LoTr 1 that consists of a K1 III giant and a hot white dwarf. The cool giant does not present any sign of s-process enhancement but is shown to have a rotation period of 6.4 d, which is a possible sign of mass accretion. LoTr 1 also presents broad double-peaked Hα emission lines, whose origin is still unclear. The nebula of LoTr 1 consists in two slightly elongated shells, with ages of 17 000 and 35 000 yr, respectively, and with different orientations. As such, LoTr 1 present a very different nebular morphology than A70 and WeBo 1, which may be an indication of difference in the mass-transfer episodes.

Description: The primary aim is to establish a firm value for the distance to the extraordinary planetary nebula KjPn 8. Secondary aims are to measure the ages of the three giant lobes of this object as well as estimate the energy in the eruption, that caused the most energetic outflow, for comparison with that of an intermediate-luminosity optical transient (ILOT). For these purposes a mosaic of images in the Hα + [N ii ] optical emission lines has been obtained with the new Aristarchos telescope in 2011 for comparison with the images of the KjPn 8 giant lobes present on the Palomar Observatory Sky Survey (POSSI-R) 1954 and POSSII-R 1991 plates. Expansion proper motions of features over this 57 yr baseline in the outflows are present. Using these, a firm distance to KjPn 8 of 1.8 ± 0.3 kpc has been derived for now the angle of the latest outflow to the sky has been established from Hubble Space Telescope imagery of the nebular core. Previously, the uncertain predictions of a bow-shock model were used for this purpose. The dynamical ages of the three separate outflows that form the giant lobes of KjPn 8 are also directly measured as 3200, 7200 and ≥5  x 10 4  yr, respectively, which confirms their sequential ejection. Moreover, the kinetic energy of the youngest and most energetic of these is measured as 10 47 erg which is compatible with an ILOT origin.

Description: Context. This paper contains results from the first 30 months of the NELIOTA project for near-Earth objects and meteoroids impacting the lunar surface. We present our analysis of the statistics concerning the efficiency of the campaign and the parameters of the projectiles and those of their impacts. Aims. The parameters of the lunar impact flashes are based on simultaneous observations in two wavelength bands. They are used to estimate the distributions of the masses, sizes, and frequency of the impactors. These statistics can have applications in both space engineering and science. Methods. The photometric fluxes of the flashes are measured using aperture photometry and their apparent magnitudes are calculated using standard stars. Assuming that the flashes follow a black body law of irradiation, the temperatures can be derived analytically, while the parameters of the projectiles are estimated using fair assumptions on their velocity and luminous efficiency of the impacts. Results. There have been 79 lunar impact flashes observed with the 1.2 m Kryoneri telescope in Greece. The masses of the meteoroids range between 0.7 g and 8 kg, and their respective sizes between 1 and 20 cm, depending on their assumed density, impact velocity, and luminous efficiency. We find a strong correlation between the observed magnitudes of the flashes and the masses of the meteoroids. Moreover, an empirical relation between the emitted energies of each band has been derived, allowing for an estimation of the physical parameters of the meteoroids that produce low energy impact flashes. Conclusions. The NELIOTA project has so far the highest detection rate and the faintest limiting magnitude for lunar impacts compared to other ongoing programs. Based on the impact frequency distribution on the Moon, we estimate that sporadic meteoroids with typical masses less than 100 g and sizes less than 5 cm enter the mesosphere of the Earth with a rate of ~108 meteoroids h−1 and also impact Moon with a rate of ~8 meteoroids h−1.

Description: One of the key methods for determining the unknown nature of Type Ia supernovae (SNe Ia) is the search for traces of interaction between the SN ejecta and the circumstellar structures at the resulting supernova remnants (SNRs Ia). So far, the observables that we receive from well-studied SNRs Ia cannot be explained self-consistently by any model presented in the literature. In this study, we suggest that the circumstellar medium (CSM) being observed to surround several SNRs Ia was mainly shaped by planetary nebulae (PNe) that originated from one or both progenitor stars. Performing two-dimensional hydrodynamic simulations, we show that the ambient medium shaped by PNe can account for several properties of the CSM that have been found to surround SNe Ia and their remnants. Finally, we model Kepler’s SNR considering that the SN explosion occurred inside a bipolar PN. Our simulations show good agreement with the observed morphological and kinematic properties of Kepler’s SNR. In particular, our model reproduces the current expansion parameter of Kepler’s SNR, the partial interaction of the remnant with a dense CSM at its northern region and finally the existence of two opposite protrusions (‘ears’) at the equatorial plane of the SNR.

Description: We present the discovery and characterization of WASP-148, a new extrasolar system that includes at least two giant planets. The host star is a slowly rotating inactive late-G dwarf with a V = 12 magnitude. The planet WASP-148b is a hot Jupiter of 0.72 RJup and 0.29 MJup that transits its host with an orbital period of 8.80 days. We found the planetary candidate with the SuperWASP photometric survey, then characterized it with the SOPHIE spectrograph. Our radial velocity measurements subsequently revealed a second planet in the system, WASP-148c, with an orbital period of 34.5 days and a minimum mass of 0.40 MJup. No transits of this outer planet were detected. The orbits of both planets are eccentric and fall near the 4:1 mean-motion resonances. This configuration is stable on long timescales, but induces dynamical interactions so that the orbits differ slightly from purely Keplerian orbits. In particular, WASP-148b shows transit-timing variations of typically 15 min, making it the first interacting system with transit-timing variations that is detected on ground-based light curves. We establish that the mutual inclination of the orbital plane of the two planets cannot be higher than 35°, and the true mass of WASP-148c is below 0.60 MJup. We present photometric and spectroscopic observations of this system that cover a time span of ten years. We also provide their Keplerian and Newtonian analyses; these analyses should be significantly improved through future TESS observations.