ALBERT

Description: Recent evidence suggests that a portion of the Canary plume travelled northeastwards below the lithosphere of the Atlas Mountains in North Africa towards the Alboran domain and was captured ~10 Ma ago by the Gibraltar subduction system in the Western Mediterranean. The capture would have been associated with the mantle return flow induced by the westward-retreating slab that would have dragged and trapped a portion of the plume material in the mantle wedge of the Gibraltar subduction zone. Such material eventually contaminated the subduction related volcanism in the Alboran region. In this work, we use scaled analogue models of slab–plume interaction to investigate the plausibility of the plume capture. An upper-mantle-scaled model combines a narrow (400 km) edge-fixed subduction plate with a laterally offset compositional plume. The subduction dominated by slab rollback and toroidal mantle flow is seen to increasingly impact on the plume dynamics as the area of influence of the toroidal flow cells at the surface is up to 500 x 1350 km 2 . While the plume head initially spreads axisymmetrically, it starts being distorted parallel to the plate in the direction of the trench as the slab trench approaches the plume edge at a separation distance of about 500 km, before getting dragged towards mantle wedge. When applied to the Canary plume–Gibraltar subduction system, our model supports the observationally based conceptual model that mantle plume material may have been dragged towards the mantle wedge by slab rollback-induced toroidal mantle flow. Using a scaling argument for the spreading of a gravity current within a channel, we also show that more than 1500 km of plume propagation in the sublithospheric Atlas corridor is dynamically plausible.

Description: We present a list of T dwarf candidates in the dark cloud L 1688 in the  Oph star-forming region. These candidates are selected with infrared colours sensitive to T dwarf characteristics of methane absorptions and of cool atmospheres. The 1.6-μm methane feature is diagnosed by on–off imaging using an H -band and an intermediate-band methane filter, calibrated to a set of known brown dwarfs of M, L, and T types in the field. Another methane feature at 3.3 μm is traced with the Spitzer /Infrared Array Camera (IRAC) [3.6] – [4.5] colour. For cool atmospheres, the H  – [4.5] and K  – [4.5] colours are utilized. With an additional criterion of mid-infrared brightness to eliminate extragalactic interlopers, a total of 28 T dwarf candidates have been identified. A comprehensive assessment was conducted to estimate the level of contamination of our sample by young stellar variability, by extragalactic sources sharing the same colour behaviour, or by foreground T dwarfs. Though extragalactic sources may contribute up to about half of the false positives, our candidates show close spatial association with the dark cloud, rather than randomly distributed as a background population would have been. Furthermore, even though our candidates are not selected a priori by a colour–magnitude relation, they mostly follow the 1 Myr isochrones, ascertaining their youth. Our selection methodology provides guidance to search for T dwarfs in other star-forming regions. Our candidate list, when comparing with those in the literature, which often rely on a single criterion on cool temperature or methane, is more conservative but should be more secure for follow-up spectroscopic confirmation of a T dwarf sample at the early evolutionary stage.

Description: How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours. In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source containing a black hole of nine solar masses (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought. This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion--not the actual rate--would then be the critical factor causing large-amplitude oscillations in long-period systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kimura, Mariko -- Isogai, Keisuke -- Kato, Taichi -- Ueda, Yoshihiro -- Nakahira, Satoshi -- Shidatsu, Megumi -- Enoto, Teruaki -- Hori, Takafumi -- Nogami, Daisaku -- Littlefield, Colin -- Ishioka, Ryoko -- Chen, Ying-Tung -- King, Sun-Kun -- Wen, Chih-Yi -- Wang, Shiang-Yu -- Lehner, Matthew J -- Schwamb, Megan E -- Wang, Jen-Hung -- Zhang, Zhi-Wei -- Alcock, Charles -- Axelrod, Tim -- Bianco, Federica B -- Byun, Yong-Ik -- Chen, Wen-Ping -- Cook, Kem H -- Kim, Dae-Won -- Lee, Typhoon -- Marshall, Stuart L -- Pavlenko, Elena P -- Antonyuk, Oksana I -- Antonyuk, Kirill A -- Pit, Nikolai V -- Sosnovskij, Aleksei A -- Babina, Julia V -- Baklanov, Aleksei V -- Pozanenko, Alexei S -- Mazaeva, Elena D -- Schmalz, Sergei E -- Reva, Inna V -- Belan, Sergei P -- Inasaridze, Raguli Ya -- Tungalag, Namkhai -- Volnova, Alina A -- Molotov, Igor E -- de Miguel, Enrique -- Kasai, Kiyoshi -- Stein, William L -- Dubovsky, Pavol A -- Kiyota, Seiichiro -- Miller, Ian -- Richmond, Michael -- Goff, William -- Andreev, Maksim V -- Takahashi, Hiromitsu -- Kojiguchi, Naoto -- Sugiura, Yuki -- Takeda, Nao -- Yamada, Eiji -- Matsumoto, Katsura -- James, Nick -- Pickard, Roger D -- Tordai, Tamas -- Maeda, Yutaka -- Ruiz, Javier -- Miyashita, Atsushi -- Cook, Lewis M -- Imada, Akira -- Uemura, Makoto -- England -- Nature. 2016 Jan 7;529(7584):54-8. doi: 10.1038/nature16452.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Graduate School of Science, Kyoto University, Oiwakecho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan. ; JEM Mission Operations and Integration Center, Human Spaceflight Technology Directorate, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan. ; MAXI team, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. ; The Hakubi Center for Advanced Research, Kyoto University, Kyoto 606-8302, Japan. ; Astronomy Department, Wesleyan University, Middletown, Connecticut 06459, USA. ; Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan. ; Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19125, USA. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. ; Steward Observatory, University of Arizona, Tucson, Arizona 85721, USA. ; Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, New York 10003, USA. ; Department of Astronomy and University Observatory, Yonsei University, Seoul 120-749, South Korea. ; Institute of Astronomy and Department of Physics, National Central University, Chung-Li 32054, Taiwan. ; Max Planck Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany. ; Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University, 452 Lomita Mall, Stanford, California 94309, USA. ; Crimean Astrophysical Observatory, 298409 Nauchny, Crimea. ; Space Research Institute, Russian Academy of Sciences, 117997 Moscow, Russia. ; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia. ; Leibniz Institute for Astrophysics, Potsdam, Germany. ; Fesenkov Astrophysical Institute, Almaty, Kazakhstan. ; Kharadze Abastumani Astrophysical Observatory, Ilia State University, Tbilisi, Georgia. ; Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulaanbaatar 13343, Mongolia. ; Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Moscow, Russia. ; Departamento de Fisica Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva, Spain. ; Center for Backyard Astrophysics, Observatorio del CIECEM, Parque Dunar, Matalascanas, 21760 Almonte, Huelva, Spain. ; Baselstrasse 133D, CH-4132 Muttenz, Switzerland. ; 6025 Calle Paraiso, Las Cruces, New Mexico 88012, USA. ; Vihorlat Observatory, Mierova 4, Humenne, Slovakia. ; Variable Star Observers League in Japan (VSOLJ), 7-1 Kitahatsutomi, Kamagaya, Chiba 273-0126, Japan. ; Furzehill House, Ilston, Swansea SA2 7LE, UK. ; Physics Department, Rochester Institute of Technology, Rochester, New York 14623, USA. ; American Association of Variable Star Observers (AAVSO), 13508 Monitor Lane, Sutter Creek, California 95685, USA. ; Institute of Astronomy, Russian Academy of Sciences, 361605 Peak Terskol, Kabardino-Balkaria, Russia. ; International Center for Astronomical, Medical and Ecological Research of National Academy of Sciences of Ukraine (NASU), 27 Akademika Zabolotnoho street, 03680 Kiev, Ukraine. ; Department of Physical Science, School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan. ; Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582, Japan. ; 1 Tavistock Road, Chelmsford, Essex CM1 6JL, UK. ; The British Astronomical Association, Variable Star Section (BAA VSS), Burlington House, Piccadilly, London W1J 0DU, UK. ; 3 The Birches, Shobdon, Leominster, Herefordshire HR6 9NG, UK. ; Polaris Observatory, Hungarian Astronomical Association, Laborc utca 2/c, 1037 Budapest, Hungary. ; 112-14 Kaminishiyama-machi, Nagasaki, Nagasaki 850-0006, Japan. ; Observatorio de Cantabria, Carretera de Rocamundo sin numero, Valderredible, Cantabria, Spain. ; Instituto de Fisica de Cantabria (CSIC-UC), Avenida Los Castros sin numero, E-39005 Santander, Cantabria, Spain. ; Agrupacion Astronomica Cantabra, Apartado 573, 39080 Santander, Spain. ; Seikei Meteorological Observatory, Seikei High School, Kichijoji-kitamachi 3-10-13, Musashino, Tokyo 180-8633, Japan. ; Center for Backyard Astrophysics (Concord), 1730 Helix Court, Concord, California 94518, USA. ; Kwasan and Hida Observatories, Kyoto University, Kitakazan-Ohmine-cho, Yamashina-ku, Kyoto 607-8471, Japan. ; Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima, Hiroshima 739-8526, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26738590" target="_blank"〉PubMed〈/a〉

Description: After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September–October. The flare was tracked from -ray to near-infrared (NIR) frequencies, including Fermi and Swift data as well as photometric and polarimetric data from several observatories. An intensive Glast-Agile support programme of the Whole Earth Blazar Telescope (GASP–WEBT) collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004–2005. We find remarkable similarity between the optical and -ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of 1 h, indicative of cospatiality of the optical and -ray emission regions. The relation between the -ray and optical fluxes is consistent with the synchrotron self-Compton (SSC) mechanism, with a quadratic dependence of the SSC -ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the -ray/optical relationship is linear during the outburst; we attribute this to changes in the Doppler factor. A strong harder-when-brighter spectral dependence is seen both the in -ray and optical non-thermal emission. This hardening can be explained by convexity of the UV–NIR spectrum that moves to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. The overall pattern of Stokes parameter variations agrees with a model of a radiating blob or shock wave that moves along a helical path down the jet.

Description: We present an analysis of the multiwavelength behaviour of the blazar OJ 248 at z  = 0.939 in the period 2006–2013. We use low-energy data (optical, near-infrared, and radio) obtained by 21 observatories participating in the Gamma-Ray Large Area Space Telescope (GLAST)- AGILE Support Program of the Whole Earth Blazar Telescope, as well as data from the Swift (optical–UV and X-rays) and Fermi (-rays) satellites, to study flux and spectral variability and correlations among emissions in different bands. We take into account the effect of absorption by the Damped Lyman α intervening system at z  = 0.525. Two major outbursts were observed in 2006–2007 and in 2012–2013 at optical and near-IR wavelengths, while in the high-frequency radio light curves prominent radio outbursts are visible peaking at the end of 2010 and beginning of 2013, revealing a complex radio–optical correlation. Cross-correlation analysis suggests a delay of the optical variations after the -ray ones of about a month, which is a peculiar behaviour in blazars. We also analyse optical polarimetric and spectroscopic data. The average polarization percentage P is less than 3 per cent, but it reaches ~19 per cent during the early stage of the 2012–2013 outburst. A vague correlation of P with brightness is observed. There is no preferred electric vector polarization angle and during the outburst the linear polarization vector shows wide rotations in both directions, suggesting a complex behaviour/structure of the jet and possible turbulence. The analysis of 140 optical spectra acquired at the Steward Observatory reveals a strong Mg  ii broad emission line with an essentially stable flux of 6.2 x 10 – 15 erg cm – 2 s – 1 and a full width at half-maximum of 2053 km s – 1 .

Description: Nature Geoscience 9, 319 (2016). doi:10.1038/ngeo2657 Authors: J. Yu, L. Menviel, Z. D. Jin, D. J. R. Thornalley, S. Barker, G. Marino, E. J. Rohling, Y. Cai, F. Zhang, X. Wang, Y. Dai, P. Chen & W. S. Broecker

Description: We present long-term photometric observations of the young open cluster IC 348 with a baseline time-scale of 2.4 yr. Our study was conducted with several telescopes from the Young Exoplanet Transit Initiative (YETI) network in the Bessel R band to find periodic variability of young stars. We identified 87 stars in IC 348 to be periodically variable; 33 of them were unreported before. Additionally, we detected 61 periodic non-members of which 41 are new discoveries. Our wide field of view was the key to those numerous newly found variable stars. The distribution of rotation periods in IC 348 has always been of special interest. We investigate it further with our newly detected periods but we cannot find a statistically significant bimodality. We also report the detection of a close eclipsing binary in IC 348 composed of a low-mass stellar component ( M 0.09 M ) and a K0 pre-main-sequence star ( M 2.7 M ). Furthermore, we discovered three detached binaries among the background stars in our field of view and confirmed the period of a fourth one.

Description: The method of virtual deep seismic sounding (VDSS) uses the large amplitude, postcritical reflection off the Moho, the SsPmp phase, to probe the Moho. In this study, we augment VDSS using the change in differential travel times between phases SsPmp and Ss ( T ) as a function of distance (moveout) to determine simultaneously both the thickness ( H ) and overall P wavespeed ( V P ) of the crust. Tests using synthetic data show that for typical uncertainties in measuring T (1 standard deviation of ±0.2 s), a minimum uncertainty of ~±1.1 km and ±0.06 km/s can be reached for nominal values of H and V P , respectively. We then demonstrate its utility with field data recorded by two permanent stations in Australia.

Description: The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO 2 in the FT unit. Decreasing the CO 2 release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure (')-Fe 2 C catalysts exhibiting low CO 2 selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO 2 . These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure (')-Fe 2 C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.

Description: 〈p〉The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO〈sub〉2〈/sub〉 in the FT unit. Decreasing the CO〈sub〉2〈/sub〉 release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure (')-Fe〈sub〉2〈/sub〉C catalysts exhibiting low CO〈sub〉2〈/sub〉 selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO〈sub〉2〈/sub〉. These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure (')-Fe〈sub〉2〈/sub〉C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.〈/p〉