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Past and future of the central double-degenerate core of Henize 2–428

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Research in Astronomy and Astrophysics 2019年第4期19卷 89-94页

作者： Dong-Hao Wu Dong-Dong Liu Bo Wang Yunnan Observatories Chinese Academy of Sciences Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences University of Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences

It has been suggested that Type Ia supernovae(SNe Ia) could be produced in the conditions of the violent merger scenario of the double-degenerate model, in which a thermonuclear explosion could be produced when a double carbon-oxygen white dwarf(CO WD) merges. It has been recently found that the nucleus of the bipolar planetary nebula Henize 2–428 consists of a double CO WD system that has a total mass of^1.76 M⊙, a mass ratio of^1 and an orbital period of^4.2 h, which is the first and only discovered progenitor candidate for an SN Ia predicted by the violent merger scenario. In this work, we aim to reproduce the evolutionary history of the central double CO WD of Henize 2–428. We find that the planetary nebula Henize 2–428 may originate from a primordial binary that has a^5.4 M⊙primary and a^2.7 M⊙secondary with an initial orbital period of^15.9 d. The double CO WD was formed after the primordial binary experienced two Roche-lobe overflows and two common-envelope ejection *** to our calculations, it takes about^840 Myr for the double CO WD to merge and form an SN Ia driven by gravitational wave radiation after their birth. To produce the current status of Henize 2–428,a large common-envelope parameter is needed. We also estimate that the rate of SNe Ia from the violent merger scenario is at most 2.9 × 10^(-4) yr^(-1), and that the delay time is in the range of^90 Myr to the Hubble time.

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

Physical properties of γ Doradus pulsating stars and their relationship with long-period δ Scuti variables

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Research in Astronomy and Astrophysics 2019年第1期19卷 1-20页

作者： Sheng-Bang Qian Lin-Jia Li Jia-Jia He Jia Zhang Li-Ying Zhu Zhong-Tao Han Yunnan Observatories Chinese Academy of Sciences Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences University of Chinese Academy of Sciences

We present LAMOST data on 168 γ Doradus(γ Dor) pulsating stars including stellar atmospheric parameters of 137 variables and spectral types for all of the samples. The distributions of period(P), temperature(T), gravitational acceleration(log(g)) and metallicity [Fe/H] are shown. It is found that most γ Dor variables are main-sequence stars with early F spectral types and temperatures from 6880 K to7280 K. They are slightly more metal poor than the Sun with a metallicity range from-0.4 to 0. On the H-R and log g-T diagrams, both the γ Dor and δ Scuti(δ Sct) stars occupy in the same region and some are beyond the borders predicted by current stellar pulsation theories. It is discovered that the physical properties of γ Dor stars are similar to those of long-period δ Sct(P > 0.3 d) stars. The stellar atmospheric parameters are all correlated with the pulsation period for short-period δ Sct variables(P < 0.3 d), but there are no such relations for γ Dor or long-period δ Sct stars. These results reveal that γ Dor and long-period δ Sct are the same group of pulsating stars and they are different from short-period δ Sct variables. Meanwhile, 33γ Dor stars are identified as candidates of binary or multiple systems.

关键词： stars:fundamental parameters stars:oscillations stars:binaries:spectroscopic stars:variables:other

More than two hundred and fifty thousand spectroscopic binary or variable star candidates discovered by LAMOST

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Research in Astronomy and Astrophysics 2019年第5期19卷 15-26页

作者： Sheng-Bang Qian Xiang-Dong Shi Li-Ying Zhu Lin-Jia Li Jia Zhang Er-Gang Zhao Zhong-Tao Han Xiao Zhou Xiao-Hui Fang Wen-Ping Liao Yunnan Observatories Chinese Academy of Sciences Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences University of Chinese Academy of Sciences

About 786.4 thousand stars were observed by LAMOST twice or more during the first stage of its spectroscopic survey. The radial velocity differences for about 256 thousand targets are larger than10 km s^(-1) and they are possible spectroscopic binary or variable candidates(SBVCs). It is shown that most SBVCs are slightly metal poorer than the Sun. There are two peaks in the temperature distribution of SBVCs around 5760 K and 4870 K, while there are three peaks in the distribution of the gravitational acceleration at 2.461, 4.171 and 4.621 cm s^(-2). The locations of SBVCs on the [Fe/H]-T, [Fe/H]-log g, log g-T and H-R diagrams are investigated. It is found that the detected SBVCs could be classified into four groups. The first group has higher log g～4.621 and lower T ～ 4870 K which are mainly cool red dwarf binaries. The second group of SBVCs has logg around 4.171 cm s^(-2) that includes binaries and pulsating stars such as δSet and γ Dor variables. The gravitational accelerations of the third group of SBVCs are higher and some of them are below the zero-age main sequence. They may be contact binaries in which the primary components are losing energy to the secondaries in the common envelopes and are at a special stellar evolutionary *** last group is composed of giants or supergiants with log g around 2.461 cm s^(-2) that may be evolved pulsating stars. One target(C134624.29+333921.2) is confirmed as an eclipsing binary with a period of 0.65 days. A preliminary analysis suggests that it is a detached binary with a mass ratio of 0.46. The primary fills its critical Roche lobe by about 89%, indicating that mass transfer will occur between the two components.

关键词： stars fundamental parameters-stars binaries spectroscopic-stars:oscillations-stars:binaries eclipsing-stars variables other

Detection of Ubiquitous Circumbinary Matter in Hot Subdwarfs Formed from Common-Envelope Ejections

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arXiv 2025年

作者： Li, Jiangdan Wolf, Christian Li, Jiao Luo, Yangping Zhao, Jingkun Chen, Bingqiu Zhang, Lin Jia, Shi Chen, Xuefei Han, Zhanwen 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Research School of Astronomy and Astrophysics Australian National University Weston CreekACT2611 Australia Centre for Gravitational Astrophysics Australian National University CanberraACT2600 Australia Department of Astronomy China West Normal University Nanchong637002 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China South-Western Institute for Astronomy Research Yunnan University Kunming650504 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

The formation of compact binary systems is largely driven by their evolution through a common envelope (CE) phase, crucial for understanding phenomena such as type Ia supernovae and black hole mergers. Despite their importance, direct observational evidence for CE material has been elusive due to the transient nature of these envelopes. Numerical simulations suggest that some envelope material may persist post-ejection. In this study, we investigate circumstellar material (CSM) surrounding hot subdwarf (sdB) stars, focusing on material ejected during the CE phase of binary evolution. We analyze Ca II K absorption lines in 727 sdB candidates from the LAMOST-LRS survey, selecting 145 stars with strong absorption features, indicating the presence of CSM. We compare the velocities of the Ca II K lines with the systemic velocities of sdB binaries, confirming that the material originates from ejected common-envelope material. The results show that the CSM persists long after the CE event, suggesting the formation of a stable, long-lived circumstellar environment around sdB stars. This study enhances our understanding of the role of CSM in post-CE evolution and provides new insights into the physical processes shaping the evolution of sdB binaries. Copyright © 2025, The Authors. All rights reserved.

关键词： Supernovae

Spectroscopic triples and a chance alignment. A solution for a problem of suspicious mass ratios for SB2s from Wilson method.

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arXiv 2023年

作者： Kovalev, Mikhail Chen, Xuefei Han, Zhanwen Yunnan Observatories China Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China Sternberg Astronomical Institute M. V. Lomonosov Moscow State University Leninskie Gory Moscow119991 Russia Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We selected three double-lined spectroscopic binary systems which have extreme mass ratios, if measured using the Wilson method. We analysed medium resolution spectroscopic observations and space-based photometry and find that all these systems are not SB2, but rather triple systems and a chance alignment of another star with SB1 that have an unseen component. Therefore suspicious mass ratios determined by the Wilson method for some double-lined spectroscopic binary systems aren’t correct as these systems are more complex. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

The environments of Type Ia supernovae with different relative equivalent width of Si II feature in their spectra

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arXiv 2022年

作者： Meng, Xiang-Cun Zhang, Ju-Jia Zhao, Xu-Lin Li, Li-Ping Wang, Xiao-Feng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Science Tianjin University of Technology Tianjin300384 China University of Chinese Academy of Sciences Beijing100049 China Tsinghua University Beijing100084 China

Although type Ia supernovae are so important in many astrophysical field, e.g. in cosmology, their explosion mechanism and progenitor system are still unclear. In physics, the relative equivalent width (REW) of the Si II 635.5 nm absorption feature reflects the velocity interval of silicon in the supernova ejecta and then may provide constraints on the explosion mechanism of SNe Ia. In this paper, we divide the SNe Ia into broad line (BL) and normal line (NL) subsamples based on their REW of Si II 635.5 nm absorption lines around maximum light, and find that the BL SNe Ia have a dimmer mean brightness than NL ones, which possibly results from their different metallicities. However, based on the pixel statistics study on the environments of two subsamples, we do not find any significant potential difference on the environments between BL and NL SNe Ia, which implies that the explosion mechanism of SNe Ia could be independent of their progenitor populations. Copyright © 2022, The Authors. All rights reserved.

关键词： Supernovae

The origin of the soft x-ray excess in the seyfert 1.5 Galaxy ESO 362-G18

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arXiv 2021年

作者： Zhong, Xiao-Gu Wang, Jian-Cheng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

We review the Seyfert 1.5 Galaxy ESO 362-G18 for exploring the origin of the soft X-ray excess. The Warm Corona and Relativistic Reflection models are two main scenarios to interpret the soft X-ray excess in AGNs at present. We use the simultaneous X-ray observation data of XMM-Newton and NuSTAR on Sep. 24th, 2016 to perform spectral analysis in two steps. First, we analyze the time-average spectra by using Warm Corona and Relativistic Reflection models. Moreover, we also explore the Hybrid model, Double Reflection model and Double Warm Corona model. We find that both of Warm Corona and Relativistic Reflection models can interpret the time-average spectra well but cannot be distinguished easily based on the time-averaged spectra fit statistics. Second, we add the RMS and covariance spectra to perform the spectral analysis with time-average spectra. The result shows that the warm corona could reproduce all of these spectra well. The the hot, optical thin corona and neutral distant reflection will increase their contribution with the temporal frequency, meaning that the corona responsible for X-ray continuum comes from the inner compact X-ray region and the neutral distant reflection is made of some moderate scale neutral clumps. © 2021, CC BY.

关键词： Galaxies

Multiwavelength Polarization Observations of Mrk 501

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arXiv 2024年

作者： Hu, Xin-Ke Yu, Yu-Wei Zhang, Jin Wang, Xiang-Gao Patra, Kishore C. Brink, Thomas G. Zheng, Wei-Kang Wang, Qi Kong, De-Feng Chen, Liang-Jun Zhou, Ji-Wang Cao, Jia-Xin Lu, Ming-Xuan Zhou, Zi-Min Wei, Yi-Ning Huang, Xin-Bo Li, Xing-Lin Lou, Hao Mao, Ji-Rong Liang, En-Wei Filippenko, Alexei V. Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China School of Physics Beijing Institute of Technology Beijing100081 China Department of Astronomy University of California BerkeleyCA94720-3411 United States 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

Mrk 501 is a prototypical high-synchrotron-peaked blazar (HBL) and serves as one of the primary targets for the Imaging X-ray Polarimetry Explorer (IXPE). In this study, we report X-ray polarization measurements of Mrk 501 based on six IXPE observations. The detection of X-ray polarization at a confidence level exceeding 99% is achieved in four out of the six observations conducted across the entire energy range (2–8 keV) of IXPE. The maximum polarization degree (ΠX) is measured to be 15.8% ± 2.8%, accompanied by a polarization angle (ψX) of 98.0◦ ± 5.1◦ at a confidence level of 5.6σ. During the remaining two observations, only an upper limit of ΠX X. The chromatic behavior of Π and the consistent values of ψ across different frequencies from X-rays to radio waves, along with the agreement between ψ and jet position angle, strongly support the interpretation of the energy-stratified model with shock-accelerated particles in the jet of Mrk 501. Additionally, the possibility of the presence of a global helical magnetic field in the jet of Mrk 501 is discussed. Copyright © 2024, The Authors. All rights reserved.

关键词： Active Galactic Nuclei

Deep search for gamma-ray emission from the accreting X-ray pulsar 1A 0535+262

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arXiv 2023年

作者： Hou, X. Zhang, W. Torres, D.F. Ji, L. Li, J. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Campus UAB Barcelona08193 Spain Barcelona08034 Spain BarcelonaE-08010 Spain School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Hefei China School of Astronomy and Space Science University of Science and Technology of China Hefei China

Binary systems are a well-established subclass of gamma-ray sources. The high mass X-ray binary pulsar 1A 0535+262 has been considered to be a possible gamma-ray emitter for a long time, although former gamma-ray searches using Fermi-LAT and VERITAS data resulted in upper limits only. We aim at a deep search for gammaray emission and pulsations from 1A 0535+262 using more than 13 years of FermiLAT data. The analysis was performed for both the whole Fermi-LAT data set, as well as for the X-ray outbursts that 1A 0535+262 has experienced since the launch of Fermi. Various X-ray observations have been used to generate the ephemeris for the pulsation search. We also investigate the long-term gamma-ray flux variability and perform orbital phase-resolved analysis for the outbursts. We did not detect any steady or pulsed gamma-ray emission from 1A 0535+262 during the whole Fermi-LAT mission span or its X-ray outbursts. We thus derived the deepest gamma-ray luminosity upper limits to date at the 95% confidence level to be around (2.3−4.7)×1032 erg s−1 depending on different spectral indices assumed, which results in a ratio of Lγ to LX (2−150 keV) being (1.9−3.9)×10−6 Copyright © 2023, The Authors. All rights reserved.

关键词： Gamma rays