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Recurring tidal disruption events a decade apart in IRAS F01004-2237

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arXiv 2024年

作者： Sun, Luming Jiang, Ning Dou, Liming Shu, Xinwen Zhu, Jiazheng Dong, Subo Buckley, David Cenko, S. Bradley Fan, Xiaohui Gromadzki, Mariusz Liu, Zhu Wang, Jianguo Wang, Tinggui Wang, Yibo Wu, Tao Yang, Lei Zhang, Fabao Zhang, Wenjie Zhang, Xiaer Department of Physics Anhui Normal University Anhui Wuhu241002 China CAS Key Laboratory for Researches in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China School of Astronomy and Space Sciences University of Science and Technology of China Hefei230026 China Center for Astrophysics Guangzhou University Guangzhou510006 China Department of Astronomy School of Physics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China Kavli Institute of Astronomy and Astrophysics Peking University 5 Yiheyuan Road Haidian District Beijing100871 China National Astronomical Observatories Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100101 China South African Astronomical Observatory P.O. Box 9 Observatory Cape Town7935 South Africa Astrophysics Science Division NASA Goddard Space Flight Center MC 661 GreenbeltMD20771 United States Steward Observatory University of Arizona 933 North Cherry Avenue Rm. N204 TucsonAZ85721-0065 United States Astronomical Observatory University of Warsaw Al. Ujazdowskie 4 Warszawa00-478 Poland Max-Planck-Institut für Extraterrestrische Physik Gießenbachstraße 1 Garching85748 Germany Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Kunming650011 China

Context. In theory, recurring tidal disruption events (TDEs) may occur when a close stellar binary encounters a supermassive black hole, if one star is captured and undergoes repeating partial TDEs, or if both stars are tidally disrupted (double TDEs). In addition, independent TDEs may be observed over decades in some special galaxies where the TDE rate is extremely high. Exploring the diversity of recurring TDEs and probing their natures with rich observational data help to understand these mechanisms. Aims. We report the discovery of a second optical flare that occurred in September 2021 in IRAS F01004-2237, where the first flare occurred in 2010 has been reported, and present a detailed analysis of multi-band data. We aim to understand the nature of the flare and explore the possible causes of the recurring flares. Methods. We describe our analysis of the position of the flare, the multi-band light curves (LCs), the optical and ultraviolet (UV) spectra, and the X-ray LC and spectra. Results. The position of the flare coincides with the galaxy centre with a precision of 650 pc. The flare peaks in ∼ 50 days with an absolute magnitude of ∼ −21 and fades in two years roughly following L ∝ t−5/3. It maintains a nearly constant blackbody temperature of ∼22,000 K in the late time. Its optical and UV spectra show hydrogen and helium broad emission lines with full width at half maxima of 7,000–21,000 km s−1 and He II/Hα ratio of 0.3–2.3. It shows weak X-ray emission relative to UV emission, with X-ray flares lasting for +1.4. These characters are consistent with a TDE, ruling out the possibilities of a supernova or an active galactic nuclei flare. With a TDE model, we infer a peak UV luminosity of 3.3 ± 0.2 × 1044 erg s−1 and an energy budget of 4.5 ± 0.2 × 1051 erg. Conclusions. A TDE caused the flare that occurred in 2021. The two optical flares separated by 10.3 ± 0.3 years can be interpreted as repeating partial TDEs, double TDEs, or two independent TDEs. Although no

关键词： Budget control

Relation of Velocity Distribution and Mass for DA White Dwarfstwo

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Chinese Astronomy and Astrophysics 2018年第2期42卷 202-212页

作者： Gong, Xiao-bo Li, Li-fang Yunnan Observatories Chinese Academy of of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China University of Chinese Academy of Sciences Beijing 100049 China

White dwarfs are the evolutionary endpoint of the low-and-medium mass stars. In the studies of white dwarfs, the mass of white dwarf is an important physical parameter. In this paper, we give an analysis about the velocity distribution of DA white dwarfs in the Sloan Digital Sky Survey (SDSS), and hope to find the relation between mass and velocity distribution of white dwarfs. We get the radial velocity and tangential velocity of every DA white dwarf according to their proper motion and spectral shift. Through analyzing the velocity distribution of DA white dwarfs, we find that the small-mass white dwarfs, which are produced from the single-star evolution channel, have a relatively large velocity dispersion. © 2018

关键词： stars: evolution Stars: fundamental parameters Stars: white dwarfs

The spectroscopic binaries from LAMOST medium-resolution survey (MRS). I. Searching for double-lined spectroscopic binaries (SB2s) with convolutional neural network

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arXiv 2021年

作者： Zhang, Bo Jing, Ying-Jie Yang, Fan Wan, Jun-Chen Ji, Xin Fu, Jian-Ning Liu, Chao Zhang, Xiao-Bin Luo, Feng Tian, Hao Zhou, Yu-Tao Wang, Jia-Xin Guo, Yan-Jun Zong, Weikai Xiong, Jian-Ping Li, Jiao Department of Astronomy Beijing Normal University Beijing100875 China Key Laboratory for Computational Astrophysics National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Kuaishou Technology Beijing100085 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Department of Astronomy School of Physics Peking University Beijing100871 China Kavli Institute for Astronomy and Astrophysics Peking University Beijing100871 China Yunnan observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

We developed a convolutional neural network (CNN) model to distinguish the double-lined spectroscopic binaries (SB2s) from others based on single exposure medium-resolution spectra (R ∼ 7, 500). The training set consists of a large set of mock spectra of single stars and binaries synthesized based on the MIST stellar evolutionary model and ATLAS9 atmospheric model. Our model reaches a novel theoretic false positive rate by adding a proper penalty on the negative sample (e.g., 0.12% and 0.16% for the blue/red arm when the penalty parameter Λ = 16). Tests show that the performance is as expected and favors FGK-type Main-sequence binaries with high mass ratio (q ≥ 0.7) and large radial velocity separation (∆v ≥ 50 km s−1). Although the real false positive rate can not be estimated reliably, validating on eclipsing binaries identified from Kepler light curves indicates that our model predicts low binary probabilities at eclipsing phases (0, 0.5, and 1.0) as expected. The color-magnitude diagram also helps illustrate its feasibility and capability of identifying FGK MS binaries from spectra. We conclude that this model is reasonably reliable and can provide an automatic approach to identify SB2s with period ≾ 10 days. This work yields a catalog of binary probabilities for over 5 million spectra of 1 million sources from the LAMOST medium-resolution survey (MRS), and a catalog of 2198 SB2 candidates whose physical properties will be analyzed in our following-up paper. Data products are made publicly available at the journal as well as our Github website. © 2021, CC BY.

关键词： Surveys

The harmonic component of the millihertz quasi-periodic oscillations in 4U 1636-53

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arXiv 2021年

作者： Fei, Zhenyan Lyu, Ming Méndez, Mariano Altamirano, D. Zhang, Guobao Mancuso, G.C. Xiang, Fu-Yuan Yang, X.J. Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China Kapteyn Astronomical Institute University of Groningen PO BOX 800 GroningenNL-9700 AV Netherlands Physics & Astronomy University of Southampton Hampshire SouthamptonSO17 1BJ United Kingdom Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Cas Kunming650216 China C.C. No. 5 Villa Elisa1894 Argentina Facultad de Ciencias Astronómicas y Geofísicas Universidad Nacional de la Plata Paseo del Bosque s/n La Plata1900 Argentina

We studied the harmonics of the millihertz quasi-periodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636-53 using the Rossi X-ray Timing Explorer observations. We detected the harmonics of the mHz QPOs in 73 data intervals, with most of them in the transitional spectra state. We found that the ratio between the rms amplitude of the harmonic and that of the fundamental remains constant in a wide range of the fundamental frequency. More importantly, we studied, for the first time, the rms amplitude of the harmonics vs. energy in 4U 1636-53 in the 2-5 keV range. We found that the rms amplitude of both the harmonic and the fundamental shows a decreasing trend as the energy increases, which is different from the behaviors reported in QPOs in certain black hole systems. Furthermore, our results suggest that not all observations with mHz QPOs have the harmonic component, although the reason behind this is still unclear. Copyright © 2021, The Authors. All rights reserved.

关键词： Stars

Magnetic-reconnection-heated corona in active galactic nuclei: refined disc–corona model and application to broad-band radiation

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arXiv 2020年

作者： Cheng, Huaqing Liu, B.F. Liu, Jieying Liu, Zhu Qiao, Erlin Yuan, Weimin School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing100049 China National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

A long-standing question in active galactic nucleus (AGN) research is how the corona is heated up to produce X-ray radiation much stronger than that arising from the viscous heating within the corona. In this paper, we carry out detailed investigations of magnetic-reconnection heating to the corona, specifically, studying how the disc and corona are self-consistently coupled with the magnetic field, and how the emergent spectra depend on the fundamental parameters of AGN. It is shown that diverse spectral shapes and luminosities over a broad bandpass from optical to X-ray can be produced from the coupled disc and corona within a limited range of the black hole mass, accretion rate and magnetic field strength. The relative strength of X-ray emission with respect to optical/ultraviolet (UV) depends on the strength of the magnetic field in the disc, which, together with accretion rate, determines the fraction of accretion energy transported and released in the corona. This refined disc–corona model is then applied to reproduce the broad-band spectral energy distributions (SEDs) of a sample of 20 bright local AGNs observed simultaneously in X-ray and optical/UV. We find that, in general, the overall observed broad-band SEDs can be reasonably reproduced, except for rather hard X-ray spectral shapes in some objects. The radiation pressure-dominant region, as previously predicted for the standard accretion disc in AGN, disappears for strong X-ray sources, revealing that AGN accretion discs are indeed commonly stable as observed. Our study suggests the disc–corona coupling model involving magnetic fields to be a promising approach for understanding the broad-band spectra of bright AGNs. Copyright © 2020, The Authors. All rights reserved.

关键词： Magnetic fields

The early-type stars from LAMOST survey: Atmospheric parameters

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arXiv 2021年

作者： Guo, YanJun Zhang, Bo Liu, Chao Li, Jiao Li, JiangDan Wang, Luqian Liu, ZhiCun Hou, Yong-Hui Han, ZhanWen Chen, XueFei Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Department of Astronomy Beijing Normal University Beijing100875 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China University of Chinese Academy of Sciences Beijing100049 China Nanjing Institute of Astronomical Optics & Technology National Astronomical Observatories Chinese Academy of Sciences Nanjing210042 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China

Massive stars play key roles in many astrophysical processes. Deriving atmospheric parameters of massive stars is important to understand their physical properties and thus are key inputs to trace their evolution. Here we report our work on adopting the data-driven technique Stellar LAbel Machine (SLAM) with the non-LTE TLUSTY synthetic spectra as the training dataset to estimate the stellar parameters of LAMOST optical spectra for early-type stars. We apply two consistency tests to verify this machine learning method and compare stellar labels given by SLAM with that in literature for several objects having high-resolution spectra. We provide the stellar labels of effective temperature (Teff), surface gravity (log g), metallicity ([M/H]), and projected rotational velocity (v sin i) for 3,931 and 578 early-type stars from LAMOST Low-Resolution Survey (LAMOST-LRS) and Medium-Resolution Survey (LAMOST-MRS), respectively. To estimate the average statistical uncertainties of our results, we calculated the standard deviation between the predicted stellar label and the pre-labeled published values from the high-resolution spectra. The uncertainties of the four parameters are σ(Teff) = 2, 185K, σ(log g) = 0.29 dex, and σ(v sin i) = 11 km s−1 for MRS, and σ(Teff) = 1, 642K, σ(log g) = 0.25 dex, and σ(v sin i) = 42 km s−1 for LRS spectra, respectively. We notice that parameters of Teff, log g and [M/H] can be better constrained using LRS spectra rather than using MRS spectra, most likely due to their broad wavelength coverage, while v sin i is constrained better by MRS spectra than by LRS spectra, probably due to the relatively accurate line profiles of MRS spectra. Copyright © 2021, The Authors. All rights reserved.

关键词： Surveys

Observational signatures of the surviving donor star in the double detonation model of Type Ia supernovae

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arXiv 2021年

作者： Liu, Zheng-Wei Röpke, Friedrich K. Zeng, Yaotian Heger, Alexander Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Science Beijing100012 China Zentrum für Astronomie der Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 Heidelberg69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg69118 Germany School of Physics and Astronomy Monash University 19 Rainforest Walk VIC3800 Australia ClaytonVIC3800 Australia StromloACT2611 Australia Joint Institute for Nuclear Astrophysics National Superconducting Cyclotron Laboratory Michigan State University 1 Cyclotron Laboratory East LansingMI48824-1321 United States

The sub-Chandrasekhar mass double-detonation (DDet) scenario is a contemporary model for Type Ia supernovae (SNe Ia). The donor star in the DDet scenario is expected to survive the explosion and to be ejected at the high orbital velocity of a compact binary system. For the first time, we consistently perform three-dimensional (3D) hydrodynamical simulations of the interaction of SN ejecta with a helium (He) star companion within the DDet scenario. We map the outcomes of 3D impact simulations into one-dimensional stellar evolution codes and follow the long-term evolution of the surviving He-star companions. Our main goal is to provide the post-impact observable signatures of surviving He-star companions of DDet SNe Ia, which will support the search for such companions in future observations. Such surviving companions are ejected with high velocities of up to about 930 km s-1. We find that our surviving He-star companions become significantly overluminous for about 106yr during the thermal re-equilibration phase. After the star re-establishes thermal equilibrium, its observational properties are not sensitive to the details of the ejecta-donor interaction. We apply our results to hypervelocity star US 708, which is the fastest unbound star in our Galaxy, travelling with a velocity of about 1,200 kms-1, making it natural candidate for an ejected donor remnant of a DDet SN Ia. We find that a He-star donor with an initial mass of 0.5Mois needed to explain the observed properties of US 708. Based on our detailed binary evolution calculations, however, the progenitor system with such a massive He-star donor cannot get close enough at the moment of SN explosion to explain the high velocity of US 708. Instead, if US 708 is indeed the surviving He-star donor of a DDet SN Ia, it would require the entire pre-SN progenitor binary to travel at a velocity of about 400 kms-1. It could, for example, have been ejected from a globular cluster in the direction of the current motion of

关键词： Detonation

Effect of Orbital Distance on the Atmospheric Escape of Exoplanets

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Chinese Astronomy and Astrophysics 2018年第1期42卷 81-100页

作者： Mo, Yang Jian-heng, Guo Yunnan Astronomical Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China University of Chinese Academy of Sciences Beijing 100049 China

Atmospheric escape is an important sector in the evolution of planetary atmosphere, and its energy is mainly originated from the radiation of the host star at the high energy band. The radiation flux drops dramatically with the increase of orbital distance, there is a large difference of planetary atmospheric escape in different orbits, so it is necessary to study the impact of orbital distance on the atmospheric escape of an exoplanet. We consider the radiation transfer and the photochemical reactions of multiple kinds of particles to study the variation of planetary atmospheric escape with the orbital distance by using a 1-D hydrodynamic model. Due to the large differences of the spectra of host stars in different evolution stages, the Astrophysical Plasma Emission Code (APEC) in the X-Ray Spectral Fitting Package (XSPEC) is used to obtain the spectra of solar-type stars with different ages as the input spectra of the model. The results indicate that the escape rates of the exoplanets in different orbits are different significantly, and the escape mechanism is converted from the drastic hydrodynamic escape into the moderate Jeans escape as the orbital distance increases, the smaller the planetary gravitational potential, the younger the star-planet system, the larger the distance of this conversion. The correlation between the escape rate and the radiation flux decreases for the short-period exoplanets in a younger star-planet system. It is shown that the classical energy-limited escape theory is not suitable for this kind of exoplanets. These results have enriched the studies on the atmospheric escape of exoplanets, especially, extended the studies on the escape mechanism and energy conversion under different orbital distances and stellar ages. © 2018 Elsevier B.V.

关键词： hydrodynamics—planets and satellites: atmospheres—stars: solar-type—X-rays: stars

The origin of UV/optical emission in the black hole low-mass X-ray binary Swift J1753.5-0127

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arXiv 2022年

作者： Yang, Pengcheng Zhang, Guobao Russell, David M. Gelfand, Joseph D. Méndez, Mariano Wang, Jiancheng Lyu, Ming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Bejing100012 China University of Chinese Academy of Sciences Bejing100049 China New York University Abu Dhabi P.O. Box 129188 Abu Dhabi United Arab Emirates Center for Astro Particle and Planetary Physics New York University Abu Dhabi P.O. Box 129188 Abu Dhabi United Arab Emirates Center for Cosmology and Particle Physics New York University 726 Broadway New YorkNY10003 United States Kapteyn Astronomical Institute University of Groningen P.O. Box 800 NL-9700 AV Groningen Netherlands Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China

The emission from the accreting black holes (BHs) in low-mass X-ray binaries (LMXBs) covers a broad energy band from radio to X-rays. Studying the correlations between emission in different energy bands during outbursts can provide valuable information about the accretion process. We analyse the simultaneous optical, ultraviolet (UV) and X-ray data of the BHLMXB Swift J1753.5-0127 during its ∼ 12-year long outburst with the Neil Gehrels Swift Observatory. We find that the UV/optical and X-ray emission are strongly correlated during the hard states of the outburst. We fit the relation with a power-law function FUV/optical∝ FβXand find that the power-law index β increases from ∼ 0.24 to ∼ 0.33 as the UV/optical wavelength decreases from ∼ 5400 Å (V) to ∼ 2030 Å (UVW2). We explore the possible reasons for this and suggest that in Swift J1753.5-0127 the UV/optical emission is dominated by a viscously heated accretion disc at large radii. We find that the data that deviate from the correlation correspond to the low-intensity peaks appeared in the X-ray band during the outburst, and suggest that these deviations are driven by the emission from the inner part of the accretion disc. Copyright © 2022, The Authors. All rights reserved.

关键词： Stars