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CENTRAL ENGINE-POWERED BRIGHT X-RAY FLARES IN SHORT GAMMA-RAY BURSTS: A HINT OF BLACK HOLE-NEUTRON STAR MERGER?

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arXiv 2018年

作者： Mu, Hui-Jun Gu, Wei-Min Mao, Jirong Hou, Shu-Jin Lin, Da-Bin Liu, Tong Department of Astronomy Xiamen University XiamenFujian361005 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan Province650011 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 Kunming650011 China College of Physics and Electronic Engineering Nanyang Normal University Nanyang Henan473061 China Guangxi Key Laboratory for Relativistic Astrophysics Department of Physics Guangxi University Nanning530004 China

Short gamma-ray bursts may originate from the merger of double neutron stars (NS) or that of a black hole (BH) and an NS. We propose that the bright X-ray flare related to the central engine reactivity may hint a BH-NS merger, since such a merger can provide more fall-back materials and therefore a more massive accretion disk than the NS-NS merger. Based on the observed 49 short bursts with Swift/X-ray Telescope follow-up observations, we find that three bursts have bright X-ray flares, among which three flares from two bursts are probably related to the central engine reactivity. We argue that these two bursts may originate from the BH-NS merger rather than the NS-NS merger. Our suggested link between the central engine-powered bright X-ray flare and the BH-NS merger event can be checked by the future gravitational wave detections from advanced LIGO and Virgo. Keywords: accretion, accretion disks — gamma-ray burst: general — X-rays: general Copyright © 2018, The Authors. All rights reserved.

关键词： Stars

GOTO065054+593624: a peculiar dwarf nova identified in real time via Kilonova Seekers

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arXiv 2025年

作者： Killestein, T.L. Ramsay, G. Kennedy, M. Kelsey, L. Steeghs, D. Littlefair, S. Godson, B. Lyman, J. Pursiainen, M. Warwick, B. Krawczyk, C. Nuttall, L.K. Wickens, E. Alexandrov, S.D. da Silva, C.M. Leadbeater, R. Ackley, K. Dyer, M.J. Jiménez-Ibarra, F. Ulaczyk, K. Galloway, D.K. Dhillon, V.S. O’Brien, P. Noysena, K. Kotak, R. Breton, R.P. Pallé, E. Pollacco, D. Kumar, A. O’Neill, D. Butterley, T. Wilson, R. Mattila, S. Sahu, A. Starling, R. Wang, C.Y. Liu, Q. Li, A. Dai, Z. Feng, H. Yuan, W. Billington, R. Bull, A.G. Gaudenzi, S. Gonano, V. Krawczyk, H. Mazzucato, M.T. Pasqua, A. da Silva Campos, J.A. Torres-Guerrero, M. Antonov, N.N. Bean, S.J. Boeneker, E.T. Brincat, S.M. Darlington, G.S. Dubois, F. Hambsch, F.-J. Messier, D. Oksanen, A. Poyner, G. Romanov, F.D. Sharp, I.D. Tordai, T. Vanmunster, T. Wenzel, K. Department of Physics & Astronomy University of Turku Vesilinnantie 5 TurkuFI-20014 Finland Armagh Observatory & Planetarium College Hill ArmaghBT61 9DG United Kingdom School of Physics University College Cork Kane Building Cork Ireland Institute of Astronomy Kavli Institute for Cosmology University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Department of Physics University of Warwick Gibbet Hill Road CoventryCV4 7AL United Kingdom Astrophysics Research Cluster School of Mathematical and Physical Sciences University of Sheffield SheffieldS3 7RH United Kingdom Institute of Cosmology and Gravitation University of Portsmouth PortsmouthPO1 3FX United Kingdom Kilonova Seekers c/o Zooniverse Department of Physics University of Oxford Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Institute of Plant Physiology and Genetics Bulgarian Academy of Sciences Acad. G. Bontchev Str. Bl.23 Sofia1113 Bulgaria American Association of Variable Star Observers 185 Alewife Brook Parkway Suite 410 CambridgeMA02138 United States Variable Stars South Royal Astronomical Society of New Zealand P O Box 3181 Wellington New Zealand British Astronomical Association Variable Star Section Burlington House Piccadilly LondonW1J 0DU United Kingdom School of Physics & Astronomy Monash University ClaytonVIC3800 Australia Instituto de Astrofísica de Canarias Tenerife La LagunaE-38205 Spain School of Physics & Astronomy University of Leicester University Road LeicesterLE1 7RH United Kingdom National Astronomical Research Institute of Thailand 260 Moo 4 T. Donkaew A. Maerim Chiangmai50180 Thailand Jodrell Bank Centre for Astrophysics Department of Physics and Astronomy The University of Manchester ManchesterM13 9PL United Kingdom Department of Physics Royal Holloway - University of London Egham Hill EghamTW20 0EX United Kingdom Centre for Advanced Instrumentation University of Durham DurhamDH1 3LE United Kingdom School of Sci

Dwarf novae are a crucial astrophysical laboratory for probing the nature of accretion, binary mass transfer, and binary evolution – yet their diverse observational characteristics continue to challenge our theoretical understanding. We here present the discovery of, and subsequent observing campaign on GOTO065054+593624 (hereafter GOTO0650), a dwarf nova of the WZ Sge type, discovered in real-time by citizen scientists via the Kilonova Seekers citizen science project. An extensive dataset charts the photometric and spectroscopic evolution of this object, covering the first two months of its 2024 superoutburst. GOTO0650 shows a complete absence of visible emission lines during the high state, strong H and barely-detected He II emission, and high-amplitude echo outbursts with a rapidly decreasing timescale that together do not neatly fit in with our current view of cataclysmic variables. The comprehensive dataset presented here not only underscores the uniqueness of this dwarf nova and marks it as a candidate period bouncer, but also highlights the important contribution that citizen scientists can make to the study of Galactic transients. Copyright © 2025, The Authors. All rights reserved.

关键词： Stars

Interstellar Scintillation observations for PSR B0355+54

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arXiv 2018年

作者： Xu, Y.H. Lee, K.J. Hao, L.F. Wang, H.G. Liu, Z.Y. Yue, Y.L. Yuan, J.P. Li, Z.X. Wang, M. Dong, J. Tan, J.J. Chen, W. Bai, J.M. Yunnan Astronomical Observatory Chinese Academy of Sciences Kunming650011 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China University of Chinese Academy of Sciences Beijing100049 China Center for Astrophysics Guangzhou University Guangzhou510006 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Xinjiang Astronomical Observatory Chinese Academy of Sciences 150 Science 1-street Urumqi Xinjiang830011 China National Astronomical Observatories Chinese Academy of Sciences Beijing China

In this paper, we report our investigation of pulsar scintillation phenomena by monitor- ing PSR B0355+54 at 2.25 GHz for three successive months using Kunming 40-m radio telescope. We have measured the dynamic spectrum, the two-dimensional correlation function, and the secondary spectrum. In those observations with high signal-to-noise ratio (S/N ≥ 100), we have detected the scintillation arcs, which are rarely observable using such a small telescope. The sub-microsecond scale width of the scintillation arc indicates that the transverse scale of structures on scattering screen is as compact as AU size. Our monitoring has also shown that both the scintillation bandwidth, timescale, and arc curvature of PSR B0355+54 were varying temporally. The plausi- ble explanation would need to invoke multiple-scattering-screen or multiple-scattering- structure scenario that different screens or ray paths dominate the scintillation process at different epochs. Copyright © 2018, The Authors. All rights reserved.

关键词： Scintillation

Comprehensive models of novae at metallicity Z = 0.02 and Z = 10−4

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arXiv 2019年

作者： Chen, Hai-Liang Woods, T.E. Yungelson, L.R. Piersanti, Luciano Gilfanov, M. Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Max Planck Institute for Astrophysics Karl-Schwarzschild-Str. 1 Garching b. München85741 Germany Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Science Beijing100012 China Institute of Gravitational Wave Astronomy School of Physics and Astronomy University of Birmingham Edgbaston BirminghamB15 2TT United Kingdom Institute of Astronomy RAS 48 Pyatnitskaya Str. Moscow119017 Russia Space Research Institute of Russian Academy of Sciences Profsoyuznaya 84/32 Moscow117997 Russia INAF – Osservatorio Astronomico d’Abruzzo via Mentore Maggini snc TeramoI-64100 Italy INFN – Sezione di Perugia via Pascoli Perugia Italy Kazan Federal University Kremlevskaya str. 18 Kazan420008 Russia

Novae are the observational manifestations of thermonuclear runaways on the surface of accreting white dwarfs (WDs). Although novae are an ubiquitous phenomenon, their properties at low metallicity are not well understood. Using the publicly-available stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), we model the evolution of accreting carbon-oxygen WDs and consider models which accrete matter with metallicity Z=0.02 or 10−4. We consider both models without mixing and with matter enriched by CO-elements assuming that mixing occurs in the process of accretion (with mixing fraction 0.25). We present and contrast ignition mass, ejected mass, recurrence period and maximum luminosity of novae for different WD masses and accretion rates for these metallicities and mixing cases. We find that models with Z = 0.02 have ignition masses and recurrence periods smaller than models with low Z, while the ejected mass and maximum luminosity are larger. Retention efficiency during novae outbursts decreases with increasing metallicity. In our implementation, inclusion of mixing at the H/He interface reduces accreted mass, ejected mass and recurrence period as compared to the no-mixing case, while the maximum luminosity becomes larger. Retention efficiency is significantly reduced, becoming negative in most of our models. For ease of use, we provide a tabular summary of our results. Copyright © 2019, The Authors. All rights reserved.

关键词： Astrophysics

A binary origin for two sequences of blue stragglers in globular cluster M30

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A binary origin for two sequences of blue stragglers in glob...

2016 Cosmic-Lab Conference: Star Clusters as Cosmic Laboratories for Astrophysics, Dynamics and Fundamental Physics, MODEST 2016

作者： Jiang, Dengkai Chen, Xuefei Li, Lifang Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

Two sequences of blue stragglers are observed in the colour-magnitude diagram of globular cluster M30, which provide an important clue to the origin of blue stragglers in globular clusters. We investigate the binary evolution channel for the formation of two bluestraggler sequences. In this channel, a star in binary system reaches the blue-straggler region by accreting matter from its companion. Employing Eggleton's stellar evolution code, we find that the binary-origin blue stragglers can appear on both sequences observed in the colourmagnitude diagram of M30 because their companions have different contribution on the total luminosity of the binary systems. Our results show that the companions of blue stragglers on the blue sequence are faint white-dwarf stars, while those on the red sequence are bright main-sequence or sub-giant stars. The binary evolution channel does not require a recent and short-lived dynamical event. © 2016 SAIt.

关键词： Giant stars

Period studies and photometric models for two EB-type binaries EU Hya and AW Vul

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Research in Astronomy and Astrophysics 2016年第2期16卷 127-134页

作者： Yuan-Gui Yang Qun Li Hua-Li Li Hai-Feng Dai School of Physics and Electronic Information/Information College Huaibei Normal UniversityHuaibei 235000China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China

New photometry for two Algol-type binaries, 0.8065 d）, was carried out using the 60-cm telescope EU Hya （P = 0.7782 d） and AW Vul （P = at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. With the updated Wilson-Devinney code, photometric el- ements were derived from the multi-color light curves. The modeled results indicate that the two systems are near-contact binaries, whose secondary components fill their Roche lobes. The fill-out factors of the primaries are fp = 81.2 （±0.2）% for EU Hya and fp --- 82.4 （±0.3）% for AW Vul. Period analysis implies that there exists a downward parabola with a light-time orbit from the （O - C） curve. This kind of periodic oscillation may be attributed to the light-time orbit effect of a third companion. The long-term period de- crease may be caused by mass and angular momentum loss. When the orbital period decreases, the fill-out factor of fp will increase. Our results indicate that the primaries will also eventually fill their Roche lobes. EU Hya and AW Vul may possibly evolve from semi-detached binaries into contact ones.

关键词： eclipsing binaries -- stars individual （EU Hya and AW Vul） -- the third companion

Accreting He-rich material onto carbon-oxygen white dwarfs until explosive carbon ignition

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Research in Astronomy and Astrophysics 2016年第10期16卷 93-98页

作者： Cheng-YuanWu Dong-Dong Liu Wei-Hong Zhou Bo Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beiiing 100049China Yunnan Minzu University Kunming 650031China

Type Ia supernovae （SNe Ia） play an important role in studies of cosmology and galactic chemi- cal evolution. They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs （CO WDs） when their masses approach the Chandrasekar （Ch） mass limit. However, it is still not completely under- stood how a CO WD increases its mass to the Ch-mass limit in the classical single-degenerate （SD） model. In this paper, we studied the mass accretion process in the SD model to examine whether the WD can explode as an SN Ia. Employing the stellar evolution code called modules for experiments in stellar as- trophysics （MESA）, we simulated the He accretion process onto CO WDs. We found that the WD can increase its mass to the Ch-mass limit through the SD model and explosive carbon ignition finally occurs in its center, which will lead to an SN Ia explosion. Our results imply that SNe Ia can be produced from the SD model through steady helium accretion. Moreover, this work can provide initial input parameters for explosion models of SNe Ia.

关键词： stars： evolution -- binaries： close -- supernovae： general -- white dwarfs

Testing relativistic boost as the cause of gamma-ray quasi-periodic oscillation in a blazar

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arXiv 2018年

作者： Yan, Dahai Zhou, Jianeng Zhang, Pengfei Zhu, Qianqian Wang, Jiancheng Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Department of General Studies Nanchang Institute of Science & Technology Nanchang330108 China

The mechanism for producing gamma-ray quasi-periodic oscillation (QPO) in blazar is unknown. One possibility is the geometric model, in which without the need for intrinsic quasi-periodic variation, the relativistic Doppler factor changes periodically, resulting in observed gamma-ray QPO. We propose a method to test this geometric model. We analyze the Fermi-LAT data of PG 1553+113 spanning from 2008 August until 2018 February. According to 29 four-month average spectral energy distributions (SEDs) in the energy range of 0.1-300 GeV, we split the Fermi-LAT energy range into three bands: 0.1-1 GeV, 1-10 GeV, and 10-300 GeV. The spectrum in each energy range can be successfully fitted by a power-law. The light curves and photon indices in the three energy ranges are obtained. Then, light curves in three narrow energy ranges, i.e., 0.2-0.5 GeV, 2-5 GeV and 20- 40 GeV, are constructed, and the relative variability amplitudes in the three narrow energy ranges are calculated. A discrete- correlation analysis is performed for the light curves. Our results indicate that (i) the light curves in the different energy ranges follow the same pattern showed in the light curve above 0.1 GeV;(ii) the three groups of photon indices in the energy ranges of 0.1-1 GeV, 1-10 GeV, and 10-300 GeV keep nearly constant;(iii) the ratio between relative variability amplitudes in different narrow energy ranges are equal (within their errors) to the prediction by the Doppler e ect. Our results support the scenario of the relativistic boost producing the gamma-ray QPO for PG 1553+113. Copyright © 2018, The Authors. All rights reserved.

关键词： Germanium alloys

Precise determination of stellar parameters of the ZZ Ceti and DAZ white dwarf GD 133 through asteroseismology

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arXiv 2019年

作者： Fu, J.-N. Vauclair, G. Su, J. Machado, L. Fox Colas, F. Kim, S.-L. Cang, T.Q. Li, C. Niu, H.B. Xue, H.F. Li, Y. Jiang, X.-J. Michel, R. Alvarez, M. Dolez, N. Ma, L. Esamdin, A. Liu, J.Z. Department of Astronomy Beijing Normal University Beijing100875 China Université de Toulouse UPS-OMP IRAP Toulouse France CNRS IRAP 14 av. Edouard Belin ToulouseF-31400 France Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Instituto de Astronomía Observatorio Astronómico Nacional San Pedro Mártir Universidad Nacional Autónoma de México Ensenada Baja california22860 Mexico IMCCE Observatoire de Paris UMR 8028 CNRS ParisF-75014 France Korea Astronomy and Space Science Institute Daejeon34055 Korea Republic of National Astrononomical Observatories Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi830011 China

An increasing number of white dwarf stars show atmospheric chemical composition polluted by heavy elements accreted from debris disk material. The existence of such debris disks strongly suggests the presence of one or more planet(s) whose gravitational interaction with rocky planetesimals is responsible for their disruption by tidal effect. The ZZ Ceti pulsator and polluted DAZ white dwarf GD 133 is a good candidate for searching for such a potential planet. We started in 2011 a photometric follow-up of its pulsations. As a result of this work in progress, we used the data gathered from 2011 to 2015 to make an asteroseismological analysis of GD 133, providing the star parameters from a best fit model with M/Mo= 0.630 ±0.002, Teff= 12400 K ±70K, log(MHe/M)= -2.00 ±0.02, log(MH/M)= -4.50 ±0.02 and determining a rotation period of ≈ 7 days. Copyright © 2019, The Authors. All rights reserved.

关键词： White dwarfs