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BROAD ABSORPTION LINE DISAPPEARANCE/EMERGENCE IN MULTIPLE IONS IN A WEAK EMISSION-LINE QUASAR

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arXiv 2018年

作者： Yi, W. Vivek, M. Brandt, W.N. Wang, T. Timlin, J. Filiz Ak, N. Schneider, D.P. Fynbo, J.P.U. Ni, Q. Vito, F. Indahl, B.L. Sameer Department of Astronomy & Astrophysics Pennsylvania State University 525 Davey Lab University ParkPA16802 United States Yunnan Observatories Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Institute for Gravitation and the Cosmos Pennsylvania State University University ParkPA16802 United States Department of Physics Pennsylvania State University University ParkPA16802 United States CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China China Faculty of Sciences Department of Astronomy and Space Sciences Erciyes University Kayseri38039 Turkey Astronomy and Space Sciences Observatory and Research Center Erciyes University Kayseri38039 Turkey Niels Bohr Institute University of Copenhagen DTU-Space Technical University of Denmark Juliane Maries Vej 30 DK-2100 Copenhagen Ø Kgs. LyngbyDK-2800 Denmark Instituto de Astrofsica and Centro de Astroingeniera Facultad de Fsica Pontificia Universidad Catolica de Chile Casilla 306 Santiago 22 Chile Chinese Academy of Sciences South America Center for Astronomy National Astronomical Observatories CAS Beijing100012 China Department of Astronomy University of Texas AustinTX78712 United States

We report the discovery of disappearance of Mg ii, Al iii, C iv, and Si iv broad absorption lines (BALs) at the same velocity (0.07c), accompanied by a new C iv BAL emerging at a higher velocity (up to 0.11c), in the quasar J0827+4252 at z = 2.038. This is the first report of BAL disappearance (i) over Mg ii, Al iii, C iv, and Si iv ions and (ii) in a weak emission-line quasar (WLQ). The discovery is based on four spectra from the SDSS and one follow-up spectrum from HET/LRS2. The simultaneous C iv BAL disappearance and emergence at different velocities, together with no variations in the CRTS light curve, indicate that ionization changes in the absorbing material are unlikely to cause the observed BAL variability. Our analyses reveal that transverse motion is the most likely dominant driver of the BAL disappearance/emergence. Given the presence of mildly relativistic BAL outflows and an apparently large C iv emission-line blueshift that is likely associated with strong bulk outflows in this WLQ, J0827+4252 provides a notable opportunity to study extreme quasar winds and their potential in expelling material from inner to large-scale regions. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Carbon stars identified from LAMOST DR4 using machine learning

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arXiv 2017年

作者： Li, Yin-Bi Luo, A-Li Du, Chang-De Zuo, Fang Wang, Meng-Xin Zhao, Gang Jiang, Bi-Wei Zhang, Hua-Wei Liu, Chao Qin, Li Wang, Rui Du, Bing Guo, Yan-Xin Wang, Bo Han, Zhan-Wen Xiang, Mao-Sheng Huang, Yang Chen, Bing-Qiu Chen, Jian-Jun Kong, Xiao Hou, Wen Song, Yi-Han Wang, You-Fen Wu, Ke-Fei Zhang, Jian-Nan Zhang, Yong Wang, Yue-Fei Cao, Zi-Huang Hou, Yong-Hui Zhao, Yong-Heng Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Beijing100190 China Department of Astronomy Beijing Normal University Beijing100875 China Department of Astronomy School of Physics Peking University Beijing100871 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650216 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China LAMOST Fellow Nanjing Institute of Astronomical Optics & Technology National Astronomical Observatories Chinese Academy of Sciences Nanjing210042 China

In this work, we present a catalog of 2651 carbon stars from the fourth Data Release (DR4) of the Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST). Using an efficient machine-learning algorithm, we find out these stars from more than seven million spectra. As a by-product, 17 carbon-enhanced metal-poor (CEMP) turnoff star candidates are also reported in this paper, and they are preliminarily identified by their atmospheric parameters. Except for 176 stars that could not be given spectral types, we classify the other 2475 carbon stars into five subtypes including 864 C-H, 226 C-R, 400 C-J, 266 C-N, and 719 barium stars based on a series of spectral features. Furthermore, we divide the C-J stars into three subtypes of CJ(H), C-J(R), C-J(N), and about 90% of them are cool N-type stars as expected from previous literature. Beside spectroscopic classification, we also match these carbon stars to multiple broadband photometries. Using ultraviolet photometry data, we find that 25 carbon stars have FUV detections and they are likely to be in binary systems with compact white dwarf companions. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

The high frequency radio emission of the galactic center magnetar sgr j1745-29 during a transitional period

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arXiv 2017年

作者： Gelfand, Joseph D. Ransom, Scott Kouveliotou, Chryssa Granot, Jonathan Van der Horst, Alexander J. Zhang, Guobao GOGUS, Ersin Roberts, Mallory S.E. Ali, Hend Al NYU Abu Dhabi United Arab Emirates NYU Center for Cosmology and Particle Physics New YorkNY10003 United States NRAO George Washington University United States WashingtonDC20052 United States Open University of Israel 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 Sabanci University Turkey Turkey

The origin of the high-frequency radio emission detected from several magnetars is poorly understood. In this paper, we report the ∼ 40 GHz properties of SGR J1745-29 as measured using Jansky Very Large Array (JVLA) and Robert C. Byrd Green Bank Telescope (GBT) observations between 2013 October 26 and 2014 May 31. Our analysis of a Q-band (45 GHz) GBT observation on 2014 April 10 resulted in the earliest detection of pulsed radio emission at high frequencies (& 20 GHz);we found that the average pulse has a singly peaked profile with width ∼ 75 ms (∼ 2% of the 3:764 s pulse period) and an average pulsed ux density of ∼ 100 mJy. We also detected very bright, short ( Copyright © 2017, The Authors. All rights reserved.

关键词： Magnetosphere

MULTI-COLOR OPTICAL MONITORING OF THE QUASAR 3C 273 FROM 2005 TO 2016

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arXiv 2017年

作者： Xiong, Dingrong Bai, Jinming Zhang, Haojing Fan, Junhui Gu, Minfeng Yi, Tingfeng Zhang, Xiong 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 Department of Physics Yunnan Normal University Kunming650500 China Center for Astrophysics Guangzhou University Guangzhou510006 China Astronomy Science and Technology Research Laboratory Department of Education of Guangdong Province Guangzhou510006 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China

We have monitored the quasar 3C 273 in optical V, R and I bands from 2005 to 2016. Intraday variability (IDV) is detected on seven nights. The variability amplitudes for most of nights are less than 10% and four nights more than 20%. When considering the nights with time spans > 4 hours, the value of duty cycle (DC) is 14.17 per cent. Over the twelve years, the overall magnitude and color index variabilities are ΔI = 0m.67, ΔR = 0m.72, ΔV = 0m.68, and Δ(V − R) = 0m.25 respectively. The largest clear IDV has an amplitude of 42% over just 5.8 minutes and the weakest detected IDV is 5.4% over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for 3C 273 and appears at different flux levels on intraday timescales. The BWB trend exists for short-term timescales and intermediate-term timescales but different timescales have different correlations. There is no BWB trend for our whole time-series data sets. A significant anti-correlation between BWB trend and length of timescales is found. Combining with V -band data from previous works, we find a possible quasi-periodicity of P = 3918 ± 1112 days. The possible explanations for the observed variability, BWB chromatic trend and periodicity are discussed. Copyright © 2017, The Authors. All rights reserved.

关键词： Galaxies

Erratum: 'Resolved Neutral Carbon Emission in Nearby Galaxies: [C i] Lines as Total Molecular Gas Tracers' (2019, ApJ, 880, 133)

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The Astrophysical Journal 2019年第2期883卷

作者： Qian Jiao Yinghe Zhao Nanyao Lu Yu Gao Dragan Salak Ming Zhu Zhi-Yu Zhang Xue-Jian Jiang Qinghua Tan Purple Mountain Observatory & Key Lab of Radio Astronomy Chinese Academy of Sciences (CAS) Nanjing 210033 People's Republic of China Yunnan Observatories & Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650011 People's Republic of China Center for Astronomical Mega-Science CAS 20A Datun Road Chaoyang District Beijing 100012 People's Republic of China China-Chile Joint Center for Astronomy (CCJCA) Camino El Observatorio 1515 Las Condes Santiago Chile National Astronomical Observatories & Key Lab of Radio Astronomy CAS Beijing 100012 People's Republic of China Purple Mountain Observatory & Key Lab of Radio Astronomy Chinese Academy of Sciences (CAS) Nanjing 210008 People's Republic of China School of Science and Technology Kwansei Gakuin University 2-1 Gakuen Sanda Hyogo 669-1337 Japan Institute for Astronomy University of Edinburgh Royal Observatory Blackford Hill Edinburgh EH9 3HJ UK ESO Karl Schwarzschild Strasse 2 D-85748 Garching Munich Germany The current zip code is corrected from that in the published article.

GeV detection of HESS J0632+057

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arXiv 2017年

作者： Li, Jian Torres, Diego F. Cheng, K.-S. de Oña Wilhelmi, Emma Kretschmar, Peter Hou, Xian Takata, Jumpei Campus UAB Carrer de Magrans s/n Barcelona08193 Spain BarcelonaE-08010 Spain Department of Physics University of Hong Kong Pokfulam Road Hong Kong Hong Kong Spain 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 School of Physics Huazhong University of Science and Technology Wuhan430074 China

HESS J0632+057 is the only gamma-ray binary that has been detected at TeV energies, but not at GeV energies yet. Based on nearly nine years of Fermi Large Area Telescope (LAT) Pass 8 data, we report here on a deep search for the gamma-ray emission from HESS J0632+057 in the 0.1–300 GeV energy range. We find a previously unknown gamma-ray source, Fermi J0632.6+0548, spatially coincident with HESS J0632+057. The measured flux of Fermi J0632.6+0548 is consistent with the previous flux upper limit on HESS J0632+057 and shows variability that can be related to the HESS J0632+057 orbital phase. We propose that Fermi J0632.6+0548 is the GeV counterpart of HESS J0632+057. Considering the Very High Energy (VHE) spectrum of HESS J0632+057, a possible spectral turnover above 10 GeV may exist in Fermi J0632.6+0548, as appears to be common in other established gamma-ray binaries. Copyright © 2017, The Authors. All rights reserved.

关键词： Gamma rays

Long-term photometric behavior of the eclipsing cataclysmic variable V729 Sgr

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arXiv 2017年

作者： Zhongtao, Han Shengbang, Qian Fernández, Lajús E. Irina, Voloshina Liying, Zhu Yunnan Observatories Chinese Academy of Sciences PO Box 110 Kunming650011 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences PO Box 110 Kunming650011 China Graduate University of the Chinese Academy of Sciences Yuquan Road 19 Sijingshang Block Beijing City100049 China Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de La Plata Paseo del Bosque s/n La Plata Pcia. Bs. As1900 Argentina Argentina Sternberg Astronomical Institute Moscow State University Universitetskij prospect 13 Moscow119992 Russia

We present the analysis results of an eclipsing cataclysmic variable (CV) V729 Sgr, based on our observations and AAVSO data. Some outburst parameters were determined such as outburst amplitude (An) and recurrence time (Tn), and then the relationship between An and Tn is discussed. A cursory examination for the long-term light curves reveals that there are small-amplitude outbursts and dips present, which is similar to the behaviors seen in some nova-like CVs (NLs). More detailed inspection suggests that the outbursts in V729 Sgr may be Type A (outside-in) with a rise time ∼ 1.76 d. Further analysis also shows that V729 Sgr is an intermediate between dwarf nova and NLs, and we constrain its mass transfer rate to 1.59 × 10−9 2 −9M☉yr−1 by combining the theory for Z Cam type stars with observations. Moreover, the rapid oscillations in V729 Sgr were detected and analyzed for the first time. Our results indicate that the oscillation at ∼ 25.5 s is a true DNO, being associated with the accretion events. The classification of the oscillations at ∼ 136 and 154 s as lpDNOs is based on the relation between PlpDNOs and PDNOs. Meanwhile, the QPOs at the period of hundreds of seconds are also detected. Copyright © 2017, The Authors. All rights reserved.

关键词： Stars

A new stellar outburst associated with the magnetic activities of the k-type dwarf in a white-dwarf binary

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arXiv 2017年

作者： Qian, S.-B. Han, Z.-T. Zhang, B. Zejda, M. Michel, R. Zhu, L.-Y. Zhao, E.-G. Liao, W.-P. Tian, X.-M. Wang, Z.-H. P.O. Box 110 Kunming650011 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of the Chinese Academy of Sciences Yuquan Road 19# Sijingshang Block Beijing100049 China Department of Theoretical Physics and Astrophysics Masaryk University Kotlářská 2 BrnoCZ-611 37 Czech Republic Instituto de Astronomía Universidad Nacional Autónoma de Méexico Ensenada Baja California Mexico

1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on June 3, 2016. Although the system was latter classified as a cataclysmic variable (CV) and the event was attributed as a dwarf-nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since April 19, 2016 and many light curves were obtained before, during and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from April 19 to September 14, 2016, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L1region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion. Copyright © 2017, The Authors. All rights reserved.

关键词： White dwarfs

The young and nearby normal type ia supernova 2018gv: UV-optical observations and the earliest spectropolarimetry

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arXiv 2019年

作者： Yang, Yi Hoeflich, Peter Baade, Dietrich Maund, Justyn R. Wang, Lifan Brown, Peter J. Stevance, Heloise F. Arcavi, Iair Burke, Jamison Cikota, Aleksandar Clocchiatti, Alejandro Gal-Yam, Avishay Graham, Melissa L. Hiramatsu, Daichi Hosseinzadeh, Griffin Howell, D. Andrew Jha, Saurabh W. McCully, Curtis Patat, Ferdinando Sand, David J. Schulze, Steve Spyromilio, Jason Valenti, Stefano Vinkao, Jozsef Wang, Xiaofeng Wheeler, J. Craig Yaron, Ofer Zhang, Jujia Department of Particle Physics and Astrophysics Weizmann Institute of Science Rehovot76100 Israel Department of Physics Florida State University TallahasseeFL32306-4350 United States European Southern Observatory Karl-Schwarzschild-Str. 2 Garching b. Munchen85748 Germany Department of Physics and Astronomy University of Sheffield Hicks Building Hounsfield Road SheffieldS37RH United Kingdom George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy Texas A. & M. University 4242 TAMU College StationTX77843 United States Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Physics Division Lawrence Berkeley National Laboratory 1 Cyclotron Road BerkeleyCA94720 United States Casilla 306 Santiago 22 Department of Astronomy University of Washington Box 351580 U.W. SeattleWA98195 United States Harvard-Smithsonian Center for Astrophysics 60 Garden Street CambridgeMA02138 United States Department of Physics and Astronomy Rutgers State University of New Jersey 136 Frelinghuysen Rd. PiscatawayNJ08854 United States Center for Computational Astrophysics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Steward Observatory University of Arizona 933 North Cherry Avenue Rm. N204 TucsonAZ85721-0065 United States Department of Physics University of California DavisCA95616 United States Konkoly Observatory MTA CSFK Konkoly Thege M. ut 15-17 Budapest1121 Hungary Department of Optics & Quantum Electronics University of Szeged Dom ter 9 Szeged6720 Hungary Department of Astronomy University of Texas at Austin AustinTX78712 United States Tsinghua University Beijing100084 Chinese Academy of Sciences

The non-detection of companion stars in Type Ia supernova (SN) progenitor systems lends support to the notion of double-degenerate (DD) systems and explosions triggered by the merging of two white dwarfs. This very asymmetric process should lead to a conspicuous polarimetric signature. By contrast, observations consistently find very low continuum polarization as the signatures from the explosion process largely dominate over the pre-explosion configuration within several days. Critical information about the interaction of the ejecta with a companion and any circumstellar matter is encoded in the early polarization spectra. In this study, we obtain spectropolarimetry of SN2018gv with the ESO Very Large Telescope at .13.6 days relative to the *** maximum light, or 5 days after the estimated explosion the earliest spectropolarimetric observations to date of any Type Ia SN. These early observations still show a low continuum polarization (-0.2%) and moderate line polarization (0.30 0.04% for the prominent Si II 6355 feature and 0.85 0.04% for the high-velocity Ca component). The high degree of spherical symmetry implied by the low line and continuum polarization at this early epoch is consistent with explosion models of delayed detonations and is inconsistent with the merger-induced explosion scenario. The dense UV and optical photometry and optical spectroscopy within the first 100 days after the maximum light indicate that SN2018gv is a normal Type Ia SN with similar spectrophotometric behavior to SN2011fe. Copyright © 2019, The Authors. All rights reserved.

关键词： Polarization