检索结果-内蒙古大学图书馆

arXiv 2019年

作者： Mauro, Mattia Di Hou, Xian Eckner, Christopher Zaharijas, Gabrijela Charles, Eric NASA Goddard Space Flight Center GreenbeltMD20771 United States Catholic University of America Department of Physics WashingtonDC20064 United States Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Center for Astrophysics and Cosmology University of Nova Gorica Vipavska 13 Nova GoricaSI-5000 Slovenia SLAC National Accelerator Laboratory Stanford University StanfordCA94305 United States

The Andromeda (M31) and Triangulum (M33) galaxies are the closest Local Group galaxies to the Milky Way, being only 785 and 870 kpc away. These two galaxies provide an independent view of high-energy processes that are often obscured in our own Galaxy, including possible signals of dark matter (DM) particle interactions. The Fermi Large Area Telescope (Fermi-LAT) preliminary eight year list of sources includes both M31, which is detected as extended with a size of about 0.4◦, and M33, which is detected as a point-like source. The spatial morphology of M31 γ-ray emission could trace a population of unresolved sources and energetic particles originating in sources not related to massive star formation. Alternatively, the γ-ray emission could also be an indication of annihilation or decay of DM particles. We investigate these two possibilities using almost 10 years of data from the Fermi LAT. An interpretation that involves only a DM γ-ray emission is in tension with the current limits from other searches, such as those targeting Milky Way dwarf spheroidal galaxies. When we include a template of astrophysical emission, tuned on γ-ray data or from observations of these galaxies in other wavelengths, we do not find any significant evidence for a DM contribution and we set limits for the annihilation cross section that probe the thermal cross section for DM masses up to a few tens of GeV in the b¯b and τ+τ− channels. For models where the DM substructures have masses above 10−6 solar masses our limits probe the DM interpretation of the Fermi LAT Galactic center excess. We provide also the lower limit for the DM decay time assuming the same spatial models of the DM distribution in M31 and M33. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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Multi-wavelength observations of the BL Lac object Fermi J1544-0649: One year after its awakening

arXiv

引用

arXiv 2020年

作者： Tam, P.H.T. Pal, P.S. Cui, Y.D. Jiang, N. Sotnikova, Y. Yang, C.W. Wang, L.Z. Tang, B.T. Li, Y.B. Mao, J. Kong, A.K.H. Zhong, Z.H. Ding, J. Mufakharov, T. Fan, J.F. Dou, L.M. Shen, R.F. Ai, Y.L. School of Physics and Astronomy Sun Yat-sen University Guangzhou510275 China CAS Key Laboratory for Researches in Galaxies and Cosmology University of Sciences and Technology of China Hefei Anhui230026 China Special Astrophysical Observatory Russian Academy of Sciences Nizhnij Arkhyz369167 Russia Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China Chinese Academy of Sciences South America Center for Astronomy China-Chile Joint Center for Astronomy Camino El Observatorio #1515 Las Condes Santiago Chile Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Institute of Astronomy National Tsing Hua University 101 Section 2. Kuang-Fu Road Hsinchu30013 Taiwan Department of Astronomy & Astrophysics University of California Santa Cruz 1156 High Street Santa CruzCA95060 United States Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China Kazan Federal University 18 Kremlyovskaya St. Kazan420008 Russia Center for Astrophysics Guangzhou University Guangzhou510006 China

We report observations of a transient source Fermi J1544-0649 from radio to γrays. Fermi J1544-0649 was discovered by the Fermi-LAT in May 2017. Followup Swift-XRT observations revealed three flaring episodes through March 2018, and the peak X-ray flux is about 103 higher than the ROSAT all-sky survey (RASS) flux upper limit. Optical spectral measurements taken by the Magellan 6.5-m telescope and the Lick-Shane telescope both show a largely featureless spectrum, strengthening the BL Lac interpretation first proposed by Bruni et al. (2018). The optical and mid-infrared (MIR) emission goes to a higher state in 2018, when the flux in high energies goes down to a lower level. Our RATAN-600m measurements at 4.8 GHz and 8.2 GHz do not indicate any significant radio flux variation over the monitoring seasons in 2017 and 2018, nor deviate from the archival NVSS flux level. During GeV flaring times, the spectrum is very hard (Γγ ∼1.7) in the GeV band and at times also very hard ((ΓX 2) in the X-rays, similar to a high-synchrotron-peak (or even an extreme) BL Lac object, making Fermi J1544-0649 a good target for ground-based Cherenkov telescopes. Copyright © 2020, The Authors. All rights reserved.

关键词： Surveys

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Formation of Extremely Low-Mass WDs in Double Degenerates

arXiv

引用

arXiv 2018年

作者： Li, Zhenwei Chen, Xuefei Chen, Hai-Liang Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science University of the Chinese Academy of Science Yuquan Road 19 Shijingshan Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China

Extremely low-mass white dwarfs (ELM WDs) are helium WDs with a mass less than ∼0.3 Mo. Most ELM WDs are found in double degenerates (DDs) in the ELM Survey led by Brown and Kilic. These systems are supposed to be significant gravitational-wave sources in the mHz frequency. In this paper, we firstly analyzed the observational characteristics of ELM WDs and found that there are two distinct groups in the ELM WD mass and orbital period plane, indicating two different formation scenarios of such objects, i.e. a stable Roche lobe overflow channel (RL channel) and common envelope ejection channel (CE channel). We then systematically investigated the formation of ELM WDs in DDs by a combination of detailed binary evolution calculation and binary population synthesis. Our study shows that the majority of ELM WDs with mass less than 0.22 Mo are formed from the RL channel. The most common progenitor mass in this way is in the range of 1.15 − 1.45 Mo and the resulting ELM WDs have a peak around 0.18 Mo when selection effects are taken into account, consistent with observations. The ELM WDs with a mass larger than 0.22 Mo are more likely to be from the CE channel and have a peak of ELM WD mass around 0.25 Mo which needs to be confirmed by future observations. By assuming a constant star formation rate of 2 Moyr−1 for a Milky Way-like galaxy, the birth rate and local density are 5 × 10−4 yr−1 and 1500 kpc−3, respectively, for DDs with an ELM WD mass less than 0.25 Mo. Copyright © 2018, The Authors. All rights reserved.

关键词： White dwarfs

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SN 2020pvb: a Type IIn-P supernova with a precursor outburst

arXiv

引用

arXiv 2024年

作者： Elias-Rosa, Nancy Brennan, Seán J. Benetti, Stefano Cappellaro, Enrico Pastorello, Andrea Kozyreva, Alexandra Lundqvist, Peter Fraser, Morgan Anderso, Joseph P. Cai, Yong-Zhi Chen, Ting-Wan Dennefeld, Michel Gromadzki, Mariusz Gutiérrez, Claudia P. Ihanec, Nada Inserra, Cosimo Kankare, Erkki Kotak, Rubina Mattila, Seppo Moran, Shane Müller-Bravo, Tomás E. Pessi, Priscila J. Pignata, Giuliano Reguitti, Andrea Reynolds, Thomas M. Smartt, Stephen J. Smith, Ken Tartaglia, Leonardo Valerin, Giorgio de Boer, Thomas Chambers, Kenneth Gal-Yam, Avishay Gao, Hua Geier, Stefan Mazzali, Paolo A. Nicholl, Matt Ragosta, Fabio Rest, Armin Yaron, Ofer Young, David R. INAF – Osservatorio Astronomico di Padova vicolo dell’Osservatorio 5 PadovaI-35122 Italy Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain The Oskar Klein Centre Department of Astronomy Stockholm University AlbaNova StockholmSE-10691 Sweden School of Physics O’Brien Centre for Science North University College Dublin Belfield Dublin 4 Ireland Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg69118 Germany European Southern Observatory Alonso de Córdova 3107 Casilla 19 Santiago Chile Nuncio Monseñor Sótero Sanz 100 Off. 104 Providencia Santiago Chile Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Graduate Institute of Astronomy National Central University 300 Jhongda Road Jhongli32001 Taiwan 98bis Boulevard Arago ParisF-75014 France Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland BarcelonaE-08034 Spain Cardiff Hub for Astrophysics Research and Technology School of Physics & Astronomy Cardiff University Queens Buildings The Parade CardiffCF24 3AA United Kingdom Tuorla Observatory Department of Physics and Astronomy University of Turku FI-20014 Finland Turku Collegium for Science Medicine and Technology University of Turku TurkuFI-20014 Finland School of Sciences European University Cyprus Diogenes street Engomi Nicosia1516 Cyprus Instituto de Alta Investigación Universidad de Tarapacá Casilla 7D Arica Chile MerateI-23807 Italy Cosmic DAWN centre Niels Bohr Institute University of Copenhagen Jagtvej 128 København N2200 Denmark Department of Physics University of Oxford Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Astrophysics Research Centre School of Mathematics and Physics Queen’s University Be

We present photometric and spectroscopic data sets for SN 2020pvb, a Type IIn-P supernova (SN) similar to SNe 1994W, 2005cl, 2009kn and 2011ht, with a precursor outburst detected (PS1 w-band ∼ -13.8 mag) around four months before the B-band maximum light. SN 2020pvb presents a relatively bright light curve peaking at MB = -17.95 ± 0.30 mag and a plateau lasting at least 40 days before it went in solar conjunction. After this, the object is no longer visible at phases > 150 days above -12.5 mag in the B-band, suggesting that the SN 2020pvb ejecta interacts with a dense spatially confined circumstellar envelope. SN 2020pvb shows in its spectra strong Balmer lines and a forest of Fe ii lines with narrow P Cygni profiles. Using archival images from the Hubble Space Telescope, we constrain the progenitor of SN 2020pvb to have a luminosity of log(L/L☉) 5.4, ruling out any single star progenitor over 50 M☉. All in all, SN 2020pvb is a Type IIn-P whose progenitor star had an outburst ∼ 0.5 yr before the final explosion, the material lost during this outburst is probably playing a role in shaping the physical properties of the supernova. Copyright © 2024, The Authors. All rights reserved.

关键词： Supernovae

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ROTATING BLACK HOLE SHADOW IN PERFECT FLUID DARK MATTER

arXiv

引用

arXiv 2018年

作者： Hou, Xian Xu, Zhaoyi Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We study analytically the shadow cast by the rotating black hole in the perfect fluid dark matter. The apparent shape of the shadow depends upon the black hole spin a and the perfect fluid dark matter intensity parameter k (k > 0). In general, the shadow is a perfect circle in the non-rotating case (a = 0) and a deformed one in the rotating case (a 6= 0). The deformation gets more and more significant with the increasing a, similar to the Schwarzschild and Kerr black holes. In addition, there exists a reflection point k0. When k 0, the size of the shadow decreases with the increasing k and the distortion increases with the increasing k. When k > k0, the size of the shadow increases with the increasing k and the distortion decreases with the increasing k. Furthermore, the energy emission rate of the black hole in the perfect fluid dark matter increases with the increasing k and the peak of the emission shifts to higher frequencies. Finally, we propose that to observe the effect of the black hole spin a and the perfect fluid dark matter intensity k on the shadow of the black hole Sgr A∗ at the center of the Milky Way, highly improved techniques would be necessary for the development of future astronomical instruments. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

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Massive stars exploding in a He-rich circumstellar medium − X. Flash spectral features in the Type Ibn SN 2019cj and observations of SN 2018jmt

arXiv

引用

arXiv 2024年

作者： Wang, Z.-Y. Pastorello, A. Maeda, K. Reguitti, A. Cai, Y.-Z. Howell, D. Andrew Benetti, S. Buckley, D. Cappellaro, E. Carini, R. Cartier, R. Chen, T.-W. Elias-Rosa, N. Fang, Q.-L. Gal-Yam, A. Gangopadhyay, A. Gromadzki, M. Gan, W.-P. Hiramatsu, D. Hu, M.-K. Inserra, C. McCully, C. Nicholl, M. Olivares, F.E. Pignata, G. Pineda-García, J. Pursiainen, M. Ragosta, F. Rau, A. Roy, R. Sollerman, J. Tartaglia, L. Terreran, G. Valerin, G. Wang, Q. Wang, S.-Q. Young, D.R. Aryan, A. Bronikowski, M. Concepcion, E. Galbany, L. Lin, H. Melandri, A. Petrushevska, T. Ramirez, M. Shi, D.-D. Warwick, B. Zhang, J.-J. Wang, B. Wang, X.-F. Zhu, X.-J. School of Physics and Astronomy Beijing Normal University Beijing100875 China Department of Physics Faculty of Arts and Sciences Beijing Normal University Zhuhai519087 China INAF - Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 Padova35122 Italy Department of Astronomy Kyoto University Kitashirakawa-Oiwake-cho Sakyo-ku Kyoto606-8502 Japan Merate23807 Italy Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States South African Astronomical Observatory PO Box 9 Observatory Cape Town7935 South Africa INAF - Osservatorio Astronomico di Roma via Frascati 33 Monte Porzio CatoneI-00078 Italy Instituto de Estudios Astrofísicos Facultad de Ingeniería y Ciencias Universidad Diego Portales Av. Ejército Libertador 441 Santiago Chile Graduate Institute of Astronomy National Central University 300 Jhongda Road Jhongli32001 Taiwan Campus UAB Carrer de Can Magrans s/n BarcelonaE-08193 Spain Department of Particle Physics and Astrophysics Weizmann Institute of Science Rehovot76100 Israel The Oskar Klein Centre Department of Astronomy Stockholm University AlbaNova StockholmSE-10691 Sweden Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China Center for Astrophysics Harvard & Smithsonian 60 Garden Street CambridgeMA02138-1516 United States The NSF AI Institute for Artificial Intelligence and Fundamental Interactions United States Department of Physics Tsinghua University Beijing10008

We present optical and near-infrared observations of two Type Ibn supernovae (SNe), SN 2018jmt and SN 2019cj. Their light curves have rise times of about 10 days, reaching an absolute peak magnitude of Mg(SN 2018jmt) = −19.07 ± 0.37 and MV(SN 2019cj) = −18.94 ± 0.19 mag, respectively. The early-time spectra of SN 2018jmt are dominated by a blue continuum, accompanied by narrow (600−1000 km s−1) He i lines with P-Cygni profile. At later epochs, the spectra become more similar to those of the prototypical SN Ibn 2006jc. At early phases, the spectra of SN 2019cj show flash ionisation emission lines of C iii, N iii and He ii superposed on a blue continuum. These features disappear after a few days, and then the spectra of SN 2019cj evolve similarly to those of SN 2018jmt. The spectra indicate that the two SNe exploded within a He-rich circumstellar medium (CSM) lost by the progenitors a short time before the explosion. We model the light curves of the two SNe Ibn to constrain the progenitor and the explosion parameters. The ejecta masses are consistent with either that expected for a canonical SN Ib (~ 2 M☉) or those from a massive WR star (> ~ 4 M☉), with the kinetic energy on the order of 1051 erg. The lower limit on the ejecta mass (> ~ 2 M☉) argues against a scenario involving a relatively low-mass progenitor (e.g., MZAMS ~ 10 M☉). We set a conservative upper limit of ~ 0.1 M☉ for the 56Ni masses in both SNe. From the light curve modelling, we determine a two-zone CSM distribution, with an inner, flat CSM component, and an outer CSM with a steeper density profile. The physical properties of SN 2018jmt and SN 2019cj are consistent with those expected from the core collapse of relatively massive, stripped-envelope (SE) stars. © 2024, CC BY.

关键词： Kinetic energy

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ALMA REVEALS A GAS-RICH, MAXIMUM-STARBURST IN THE HYPERLUMINOUS, DUST-OBSCURED QUASAR W0533−3401 AT z ∼ 2.9

arXiv

引用

arXiv 2019年

作者： Fan, Lulu Knudsen, Kirsten K. Han, Yunkun Tan, Qing-hua CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China HefeiAnhui230026 China Shandong Provincial Key Lab of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Science Shandong University Weihai264209 China Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-439 92 Sweden Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Purple Mountain Observatory & Key Laboratory for Radio Astronomy Chinese Academy of Sciences 8 Yuanhua Road Nanjing210034 China

We present ALMA observations and multiwavelength spectral energy distribution (SED) analysis in a WISE-selected, hyperluminous dust-obscured quasar W0533−3401 at z = 2.9. We derive its physical properties of each component, such as molecular gas, stars, dust and the central supermassive black hole (SMBH). Both the dust continuum at 3 mm and the CO(3 − 2) line are detected. The derived molecular gas mass Mgas = 8.4 × 1010 M☉ and its fraction fgas = 0.7 suggest that W0533−3401 is gas-rich. The star formation rate (SFR) has been estimated to be ∼ 3000 − 7000 M☉ yr−1 by using different methods. The high values of SFR and specific SFR suggest that W0533−3401 is a maximum-starburst. The corresponding gas depletion timescales are very short (tdepl ∼ 12 − 28 Myr). The CO(3 − 2) emission line is marginally resolved and has a velocity gradient, which is possibly due to a rotating gas disk, gas outflow or merger. Finally, we infer the black hole mass growth rate of W0533−3401 (Ṁ BH = 49 M☉ yr−1), which suggests a rapid growth of the central SMBH. The observed black hole to stellar mass ratio MBH/M* of W0533−3401, which is dependent on the adopted Eddington ratio, is over one order of magnitude higher than the local value, and is evolving towards the evolutionary trend of unobscured quasars. Our results are consistent with the scenario that W0533−3401, with both a gas-rich maximum-starburst and a rapid black hole growth, is experiencing a short transition phase towards an unobscured quasar. Copyright © 2019, The Authors. All rights reserved.

关键词： Galaxies

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Photometric and spectroscopic studies of superoutbursts of three dwarf novae independently identified by the SVOM/GWAC system in 2018

arXiv

引用

arXiv 2019年

作者： Wang, J. Li, H.L. Xin, L.P. Han, X.H. Meng, X.M. Brink, T.G. Cai, H.B. Dai, Z.G. Filippenko, A.V. Hsia, C.-H. Huang, L. Jia, L. Li, G.W. Li, Y.B. Liang, E.W. Lu, X.M. Mao, J. Qiu, P. Qiu, Y.L. Ren, J.J. Turpin, D. Wang, H.J. Wang, X.G. Wang, X.Y. Wu, C. Xu, Y. Yan, J.Z. Zhang, J.B. Zheng, W. Wei, J.Y. Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Department of Astronomy University of California BerkeleyCA94720-3411 United States School of Astronomy and Space Science Nanjing University Nanjing210000 China State Key Laboratory of Lunar and Planetary Sciences Macau University of Science and Technology Taipa999078 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210034 China

We report our photometric and spectroscopic follow-up observations of the superoutbursts of three dwarf novae (GWAC 180415A, GWAC 181017A and GWAC 181211A) identified independently by the Ground Wide-angle Cameras system, one of the ground-based instruments of the China-France SVOM mission. Based on a combination of our photometry and that taken from the AAVSO, our period analysis of the superhumps enables us to determine the mass ratios to be 0.0967-0.1163, 0.1879-0.1883 and 0.0981-0.1173 for GWAC 180415A, GWAC 181017A and GWAC 181211A, respectively. GWAC 180415A can be firmly identified as a WZ sge-type dwarf novae due to its long duration (∼ 2 weeks) multiple rebrightenings with amplitudes of 3-4 magnitudes, the early superhump associated with a double-wave modulation and the low mass ratio. The inferred low mass ratio and location in the Ε − Porb diagram suggest that GWAC 181211A is a WZ sge-type dwarf novae candidate. The measured Balmer decrements suggest the Balmer line emission is produced from an optical thick region in GWAC 180415A and GWAC 181017A, and from an optical thin region in GWAC 181211A. Copyright © 2019, The Authors. All rights reserved.

关键词： Photometry

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Star-formation rates of two GRB host galaxies at z ∼ 2 and a [C ii] deficit observed with ALMA

arXiv

引用

arXiv 2019年

作者： Hashimoto, Tetsuya Hatsukade, Bunyo Goto, Tomotsugu Kim, Seong Jin Ohta, Kouji Nagao, Tohru Kong, Albert K.H. Nakanishi, Kouichiro Mao, Jirong Institute of Astronomy National Tsing Hua University 101 Section 2. Kuang-Fu Road Hsinchu30013 Taiwan Institute of Astronomy Graduate School of Science University of Tokyo 2-21-1 Osawa Mitaka Tokyo181-0015 Japan Department of Astronomy Kyoto University Kitashirakawa-Oiwake-cho Sakyo-ku Kyoto Kyoto606-8502 Japan Research Center for Space and Cosmic Evolution Ehime University MatsuyamaEhime790-8577 Japan National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

Event rate of long Gamma-Ray Bursts (GRBs) is expected to be an useful tracer of the cosmic star-formation history. For this purpose, it is necessary to understand what kind of star formations/galaxies are traced by GRBs. Here we report rest-frame far-infrared (FIR) continuum detections of GRB 070521 and 080207 host galaxies at z ∼ 2 with ALMA band 8 and 9. The FIR photometries provide the reliable star-formation rates (SFRs), because FIR emission is free from dust extinction and possible radio contamination from long-lived afterglows of GRBs. The spectral energy distribution fittings indicate 49.85+−722.86.33 and 123.4+−2521..1978 M yr−1 for the 070521 and 080207 hosts, respectively. The derived SFRs place them on the "main sequence" of normal star-forming galaxies at z ∼ 2. The derived SFRs are significantly lower than that of radio observations. It is inferred that the observed radio fluxes in a previous study are contaminated by the afterglows. ALMA marginally detected [C ii] 158 µm emission line from the GRB 080207 host galaxy with S/N ∼ 4. This is the first detection of [C ii] 158 µm of a GRB host at z > 2, and the second detection among known GRBs. The luminosity ratio of [C ii] 158µm to FIR is 7.5×10−4, which is one of the smallest values among galaxies at z ∼ 1 − 2 with the same FIR luminosity. The "[C ii] deficit" could be a new physical property to characterise GRB hosts at z ∼ 1 − 2. Possible parameters controlling the deficit include the metallicity, initial mass function, and gas density. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

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A Close-in Substellar Object Orbiting the sdOB-type Eclipsing-Binary System NSVS14256825

arXiv

引用

arXiv 2019年

作者： Zhu, L.-Y. Qian, S.-B. Lajús, Fernández E. Wang, Z.-H. Li, L.-J. P. O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Facultad de Ciencias AstronómicasyGeofísicas Universidad Nacional de La Plata La PlataBuenos Aires1900 Argentina La Plata BA Paseo del Bosque s/n B1900FWA Argentina

NSVS 14256825 is the second sdOB + dM eclipsing binary systems with an orbital period of 2.65 hours. The special binary was reported to contain circumbinary planets or brown dwarfs by using the timing method. However, different results were derived by different authors because of the insufficient coverage of eclipse timings. Since 2008, we have monitored this binary for about 10 years by using several telescopes and 84 new times of light minimum in high precision were obtained. It is found that the O-C curve is increasing recently and it shows a cyclic variation with a period of 8.83 years and amplitude of 46.31 seconds. The cyclic change cannot be explained by magnetic activity cycles of the red-dwarf component because the required energy is much larger than that radiated by this component in one whole period. This cyclic change detected in NSVS1425 could be explained by the light-travel time effect via the presence of a third body. The lowest mass of the third body is determined as 14.15 Mjup that is in the transition between planets and brown dwarfs. The substellar object is orbiting around this evolved binary at an orbital separation around 3 AU with an eccentricity of 0.12. These results indicate that NSVS 14256825 is the first sdOB-type eclipsing binary consisting of a hierarchical substellar object. The detection of a close-in substellar companion to NSVS 14256825 will provide some insights on the formation and evolution of sdOB-type binaries and their companions. Copyright © 2019, The Authors. All rights reserved.

关键词： Systems (metallurgical)

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