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A low-mass-ratio and deep contact binary as the progenitor of the merger V1309 Sco

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Research in Astronomy and Astrophysics 2016年第4期16卷 129-132页

作者： Li-Ying Zhu Er-Gang Zhao Xiao Zhou Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China University of the Chinese Academy of Sciences Beijing 100049China

Nova Sco 2008 （=V1309 Sco） is an example of a V838 Mon type eruption rather than a typical classical nova. This enigmatic object was recently shown to have resulted from the merger of two stars in a contact binary. It is the first stellar merger that was identified to be undergoing a common envelope transient. To understand the properties of its binary progenitor, the pre-outburst light curves were analyzed by using the W-D method. The photometric solution of the 2002 light curve shows that it is a deep contact binary （f = 89.5（~40.5）%） with a mass ratio of 0.094. The asymmetry of the light curve is explained by the presence of a dark spot on the more massive component. The extremely high fill-out factor suggests that the merging of the contact binary is driven by dynamical mass loss from the outer Lagrange point. However, the analysis of the 2004 light curve indicates that no solutions were obtained even at an extremely low mass ratio of q = 0.03. This suggests that the common convective envelope of the binary system disappeared and the secondary component spiraled into the envelope of the primary in 2004. Finally, the ejection of the envelope of the primary produced the outburst.

关键词： stars： binaries： close -- stars： binaries： eclipsing -- stars： individuals （V1309 Sco） -- stars：evolution -- stars： mass-loss

Optical and γ-ray variability behaviors of 3C 454.3 from 2006 to 2011

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arXiv 2018年

作者： Fan, Xu-Liang Li, Shao-Kun Liao, Neng-Hui Chen, Liang Liu, Hong-Tao Lu, Kai-Xing Yan, Da-Hai Zhang, Rui-Yu Guo, Qian Wu, Qingwen Bai, Jin-Ming School of Physics Huazhong University of Science and Technology Wuhan430074 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Nanjing210008 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China University of Chinese Academy of Sciences Beijing100049 China

We present our photometric monitoring of a flat spectrum radio quasar (FSRQ) 3C 454.3 at Yunnan observatories from 2006 to 2011. We find that the optical color of 3C 454.3 shows obvious redder-when-brighter trend, which reaches a saturation stage when the source is brighter than 15.15 mag at V band. We perform a simulation with multiple values of disk luminosity and spectral index to reproduce the magnitude-color diagram. The results show that the contamination caused by the disk radiation alone is difficult to produce the observed color variability. The variability properties during the outburst in December 2009 are also compared with γ-ray data derived from Fermi γ-ray space telescope. The flux variation of these two bands follow a linear relation with Fγ∝ FR1.14±0.07, which provides an observational evidence for external Compton process in 3C 454.3. Meanwhile, this flux correlation indicates that electron injection is the main mechanism for variability origin. We also explore the variation of the flux ratio Fγ/FRand the detailed structures in the lightcurves, and discuss some possible origins for the detailed variability behaviors. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Ring galaxies through off-center minor collisions by tuning bulge-to-disk mass ratio of progenitors

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arXiv 2018年

作者： Chen, Guangwen Wu, Xufen Kong, Xu Liu, Wen-Juan Zhao, Hong Sheng 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 Science University of Science and Technology of China Hefei230026 China Yunnan Observatories Chinese Academy of Sciences Kunming Yunnan650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming Yunnan650011 China School of Physics and Astronomy University of St Andrews North Haugh FifeKY16 9SS United Kingdom

Collisional ring galaxies (CRGs) are formed through off-center collisions between a target galaxy and an intruder dwarf galaxy. We study the mass distribution and kinematics of the CRGs by tuning the bulge-to-disk mass ratio (B/D) for the progenitor;i.e., the target galaxy. We find that the lifetime of the ring correlates with the initial impact velocity vertical to the disk plane (i.e., vz0). Three orbits for the collisional galaxy pair, on which clear and asymmetric rings form after collisions, are selected to perform the N-body simulations at different values of B/D for the progenitor. It is found that the ring structures are the strongest for the CRGs with small values of B/D. The Sérsic index, n, of the central remnant in the target galaxy becomes larger after collision. Moreover, the Sérsic index of a central remnant strongly correlates with the initial value of B/D for the progenitor. A bulge-less progenitor results in a late-type object in the center of the ring galaxy, whereas a bulge-dominated progenitor leads to an early-type central remnant. Progenitors with B/D ∈ [0.1, 0.3] (i.e., minor bulges) leave central remnants with n ≈ 4. These results provide a possible explanation for the formation of a recently observed CRG with an early-type central nucleus, SDSS J1634+2049. In addition, we find that the radial and azimuthal velocity profiles for a ring galaxy are more sensitive to the B/D than the initial relative velocity of the progenitor. Su. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

Impact of plasma instability on constraint of the intergalactic magnetic field

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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 Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Department of General Studies Nanchang Institute of Science & Technology Nanchang330108 China

A relativistic electron-positron pair beam can be produced in the interaction of TeV photons from a blazar with the extragalactic background light (EBL). The relativistic e± pairs would loss energy through inverse-Compton scattering (ICS) photons of cosmic microwave background (CMB) or plasma instabilities. The dominant energy-loss process is under debate. Based on the assumption that the dominant energy-loss process is ICS, the resulted cascade GeV radiation is usually used to constrain the intergalactic magnetic field (IGMF). Here, we include the energy-loss due to plasma oblique instability in the calculation of cascade gamma-ray flux, and investigate the impact of the plasma instability on the constraint of IGMF. The up-to-date GeV data and archival TeV data of the blazar 1ES 0229+200 are used. The results indicate that even if the oblique instability cooling is dominating over ICS cooling, the cascade flux could be still used to constrain the IGMF. It is found that with the ratio between the cooling rates of the oblique instability and the ICS varying from 0.1, 1 to 10, the lower limit of the IGMF putted by the cascade flux and the gamma-ray data changes from 8 × 10−18 G, 5 × 10−18 G to 10−18 G. If the ratio between the two cooling rates is 30, the estimate of IGMF based on the cascade flux is invalid. Copyright © 2018, The Authors. All rights reserved.

关键词： Magnetic fields

Expanded solutions of force-free electrodynamics on general Kerr black holes

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Physical Review D 2017年第2期96卷 023014-023014页

作者： Huiquan Li Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences 650216 Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 650216 Kunming China and Center for Astronomical Mega-Science Chinese Academy of Sciences 100012 Beijing China

In this work, expanded solutions of force-free magnetospheres on general Kerr black holes are derived through a radial distance expansion method. From the regular conditions both at the horizon and at spatial infinity, two previously known asymptotical solutions (one of them is actually an exact solution) are identified as the only solutions that satisfy the same conditions at the two boundaries. Taking them as initial conditions at the boundaries, expanded solutions up to the first few orders are derived by solving the stream equation order by order. It is shown that our extension of the exact solution can (partially) cure the problems of the solution: it leads to magnetic domination and a mostly timelike current for restricted parameters.

关键词： Electromagnetic radiation astronomy

Massive stars, successes and challenges

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arXiv 2017年

作者： Meynet, Georges Maeder, André Georgy, Cyril Ekström, Sylvia Eggenberger, Patrick Barblan, Fabio Song, Han Feng Department of Astronomy University of Geneva Switzerland College of Science Guizhou University GuiyangGuizhou Province550025 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

We give a brief overview of where we stand with respect to some old and new questions bearing on how massive stars evolve and end their lifetime. We focus on the following key points that are further discussed by other contributions during this conference: convection, mass losses, rotation, magnetic field and multiplicity. For purpose of clarity, each of these processes are discussed on its own but we have to keep in mind that they are all interacting between them offering a large variety of outputs, some of them still to be discovered. Copyright © 2017, The Authors. All rights reserved.

关键词： Magnetic fields

On the origin of the hard X-Ray excess of high-synchrotron-peaked BL Lac object Mrk 421

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arXiv 2017年

作者： Chen, Liang Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

For the first time, Kataoka & Stawarz reported a clear detection of a hard X-ray excess, above ≿20 keV, in the high-synchrotron-peaked BL Lac object Mrk 421. We find that this feature may not be produced by the low-energy part of the same electron population that produced the Fermi/LAT γ-ray. Because of that it is required that the power-law electron energy go down to γmin ≈ 19, which predicts a very strong radio emission (radio flux larger than the observed) even considering the synchrotron self-absorption effect. We investigate the possibility of this excess being produced from the spine/layer jet structure, which has been clearly detected in Mrk 421. We find that (1) similar to one-zone modeling, the spine emissions provide good modeling of the broadband spectral energy distribution, except for the hard X-ray excess;and (2) the hard X-ray excess can be well represented by the synchrotron photons (from the layer) being inverse Compton scattered by the spine electrons. Copyright © 2017, The Authors. All rights reserved.

关键词： Gamma rays

The Intermediate-Mass Black Hole Reverberation Mapping Project: First Detection of Mid-Infrared Lags in Prototypical IMBHs in NGC 4395 and POX 52

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arXiv 2025年

作者： Sun, Jingbo Guo, Hengxiao Zuo, Wenwen Lira, Paulina Gu, Minfeng Edwards, Philip G. Wang, Shu Stevens, Jamie An, Tao Barua, Samuzal Cai, Zhen-Yi Feng, Haicheng Gupta, Alok C. Ho, Luis C. Ilić, Dragana Kovačević, Andjelka B. Li, ShaSha Mezcua, Mar Popović, Luka Č. Sánchez-Sáez, Paula Sun, Mouyuan Shen, Rongfeng Vivian, U. Vince, Oliver Wang, Junxian Wu, Xuebing Yu, Zhefu Zheng, Zhenya Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Departamento de Astronom ìa Universidad de Chile Casilla 36D Santiago Chile CSIRO Astronomy and Space Science PO Box 76 EppingNSW1710 Australia Department of Physics & Astronomy Seoul National University Seoul08826 Korea Republic of Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China School of Astronomy and Space Science University of Science and Technology of China Hefei230026 China Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Yunnan Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Yunnan Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Manora Peak Nainital263001 India Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China University of Belgrade Faculty of Mathematics Department of Astronomy Studentski trg 16 Belgrade Serbia Hamburger Sternwarte Universitat Hamburg Gojenbergsweg 112 HamburgD-21029 Germany Campus UAB Carrer de Magrans Barcelona08193 Spain Edifici RDIT Campus UPC Castelldefels Barcelona08860 Spain Astronomical Observatory Volgina 7 Belgrade11060 Serbia European Southern Observatory Karl-Schwarzschild-Str. 2 Garching85748 Germany Department of Astronomy Xiamen University Fujian Xiamen361005 China School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China CSST Science Center for the Guangdong-Hongkong-Macau Greater Bay Area Sun Yat-Sen University Zhuhai519082 China IPAC Caltech 1200 E. California Blvd. PasadenaCA91125 United States Department of Physics and Astr

The search for robust evidence of intermediate-mass black holes (IMBHs) is crucial for understanding black hole seeding process and the formation of supermassive black holes in the early Universe. NGC 4395 and POX 52 are two prototypical IMBH hosts, both exhibiting multi-line evidence of low-mass black hole activity. Here, we report the first detection of mid-infrared (MIR) lags in response to optical variability, with measurements of 3.0+2−149 days for NGC 4395 and 35.2+14−1127 days for POX 52 at 3.4 µm, respectively, using archival optical data and observations from the Wide-field Infrared Survey Explorer (WISE). This detection provides the first reverberation evidence of low-mass black hole activity in POX 52. The time lags of these two low-mass, low-luminosity active galactic nuclei (AGNs) generally follow the extent of the Rdust − L5100 relation found in higher-mass AGNs. Based on an empirical relation between the broad-line region and dusty torus size, we constrain the black hole mass of POX 52 to log(MBH/M☉) = 5.5 ± 0.37 (systemic and statistical errors), confirming its IMBH nature. Furthermore, long-term optical continuum monitoring of POX 52 reveals a mild inter-band lag of 1 day. However, no significant intranight variability was detected during its one-night, high-cadence monitoring, which we attribute to the longer duty cycle of fast variability in POX 52 compared to that in NGC 4395. © 2025, CC BY.

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A lower occurrence rate of bright X-ray flares in SN-GRBs than z < 1 GRBs: Evidence of energy partitions?

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arXiv 2018年

作者： Mu, Hui-Jun Gu, Wei-Min Mao, Jirong Liu, Tong Hou, Shu-Jin Lin, Da-Bin Wang, Junfeng Fang, Taotao Liang, En-Wei Department of Astronomy Xiamen University Xiamen Fujian361005 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

关键词： Supernovae