ALBERT

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: We combine spatial variations of P- and S-wave speeds, 1000 fault plane solutions, and 6600 well-determined hypocenters to investigate the nature of subducted lithosphere and deep earthquakes beneath the Tonga back-arc. We show that perplexing patterns in seismicity and fault plane solutions can be accounted for by the juxtaposition of a steep-dipping Wadati-Benioff zone and a subhorizontal remnant of slab that is no longer attached to the actively subducting lithosphere. The detached slab may be from a previous episode of subduction along the fossil Vitiaz trench about 5 to 8 million years ago. The juxtaposition of slabs retains a large amount of subducted material in the transition zone of the mantle. Such a configuration, if common in the past, would allow the preservation of a primordial component in the lower mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chen, W P -- Brudzinski, M R -- New York, N.Y. -- Science. 2001 Jun 29;292(5526):2475-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology, University of Illinois, Urbana, IL 61801, USA. w-chen@uiuc.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11431564" target="_blank"〉PubMed〈/a〉

Description: We combined precise focal depths and fault plane solutions of more than 40 events from the 20 September 1999 Chi-Chi earthquake sequence with a synthesis of subsurface geology to show that the dominant structure for generating earthquakes in central Taiwan is a moderately dipping (20 degrees to 30 degrees ) thrust fault away from the deformation front. A second, subparallel seismic zone lies about 15 kilometers below the main thrust. These seismic zones differ from previous models, indicating that both the basal decollement and relic normal faults are aseismic.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kao -- Chen -- New York, N.Y. -- Science. 2000 Jun 30;288(5475):2346-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Earth Sciences, Academia Sinica, Nankang, Taipei, Taiwan 115, Republic of China. Department of Geology and Mid-America Earthquake (MAE) Center, University of Illinois, Urbana, IL 61801, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10875915" target="_blank"〉PubMed〈/a〉

Description: Strong evidence exists that water is carried from the surface into the upper mantle by hydrous minerals in the uppermost 10-12 km of subducting lithosphere, and more water may be added as the lithosphere bends and goes downwards. Significant amounts of that water are released as the lithosphere heats up, triggering earthquakes and fluxing arc volcanism. In addition, there is experimental evidence for high solubility of water in olivine, the most abundant mineral in the upper mantle, for even higher solubility in olivine's high-pressure polymorphs, wadsleyite and ringwoodite, and for the existence of dense hydrous magnesium silicates that potentially could carry water well into the lower mantle (deeper than 1,000 km). Here we compare experimental and seismic evidence to test whether patterns of seismicity and the stabilities of these potentially relevant hydrous phases are consistent with a wet lithosphere. We show that there is nearly a one-to-one correlation between dehydration of minerals and seismicity at depths less than about 250 km, and conclude that the dehydration of minerals is the trigger of instability that leads to seismicity. At greater depths, however, we find no correlation between occurrences of earthquakes and depths where breakdown of hydrous phases is expected. Lastly, we note that there is compelling evidence for the existence of metastable olivine (which, if present, can explain the distribution of deep-focus earthquakes) west of and within the subducting Tonga slab and also in three other subduction zones, despite metastable olivine being incompatible with even extremely small amounts of water (of the order of 100 p.p.m. by weight). We conclude that subducting slabs are essentially dry at depths below 400 km and thus do not provide a pathway for significant amounts of water to enter the mantle transition zone or the lower mantle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Green, Harry W 2nd -- Chen, Wang-Ping -- Brudzinski, Michael R -- England -- Nature. 2010 Oct 14;467(7317):828-31. doi: 10.1038/nature09401. Epub 2010 Oct 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Geophysics and Planetary Physics and Department of Earth Sciences, University of California, Riverside, California 92521, USA. harry.green@ucr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20927105" target="_blank"〉PubMed〈/a〉

Description: Eleven intracontinental earthquakes, with magnitudes ranging from 4.9 to 6, occurred in the mantle beneath the western Himalayan syntaxis, the western Kunlun Mountains, and southern Tibet (near Xigaze) between 1963 and 1999. High-resolution seismic waveforms show that some focal depths exceeded 100 kilometers, indicating that these earthquakes occurred in the mantle portion of the lithosphere, even though the crust has been thickened there. The occurrence of earthquakes in the mantle beneath continental regions where the subduction of oceanic lithosphere ceased tens of millions years ago indicates that the mantle lithosphere is sufficiently strong to accumulate elastic strain.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chen, Wang-Ping -- Yang, Zhaohui -- New York, N.Y. -- Science. 2004 Jun 25;304(5679):1949-52.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15218145" target="_blank"〉PubMed〈/a〉

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〉