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arXiv 2022年

作者： Zhang, Qian-Sheng Christensen-Dalsgaard, Jørgen Li, Yan Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Kunming650216 China Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University Aarhus CDK-8000 Denmark 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 University of Chinese Academy of Sciences Beijing100049 China

Convective-core overshoot mixing is a significant uncertainty in stellar evolution. Because numerical simulations and turbulent convection models predict exponentially decreasing radial rms turbulent velocity, a popular treatment of the overshoot mixing is to apply a diffusion process with exponentially decreasing diffusion coefficient. It is important to investigate the parameters of the diffusion coefficient because they determine the efficiency of the mixing in the overshoot region. In this paper, we have investigated the effects of the core overshoot mixing on the properties of the core in solar models and have constrained the parameters of the overshoot model by using helioseismic inferences and the observation of the solar 8B neutrino flux. For solar-mass stars, the core overshoot mixing helps to prolong the lifetime of the convective core developed at the ZAMS. If the strength of the mixing is sufficiently high, the convective core in a solar model could survive till the present solar age, leading to large deviations of the sound-speed and density profiles comparing with the helioseismic inferences. The 8B neutrino flux also favours a radiative solar core. Those provide a constraint on the parameters of the exponential diffusion model of the convective overshoot mixing. A limited asteroseismic investigation of 13 Kepler low-mass stars with 1.0 © 2022, CC BY.

关键词： Mixing

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Monte-Carlo simulations on possible collimation effects of outflows to fan-beamed emission of ultraluminous accreting X-ray pulsars

arXiv

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arXiv 2022年

作者： Hou, X. You, Y. Ji, L. Soria, R. Zhang, S.N. Ge, M.Y. Tao, L. Zhang, S. Feng, H. Zhou, M. Tuo, Y.L. Song, L.M. Wang, J.C. Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China Sydney Institute for Astronomy School of Physics A28 The University of Sydney SydneyNSW2006 Australia Department of Astronomy Tsinghua University Beijing100084 China

Pulsating ultraluminous X-ray sources (PULXs) are accreting pulsars with apparent X-ray luminosity exceeding 1039 erg s−1. We perform Monte-Carlo simulations to investigate whether high collimation effect (or strong beaming effect) is dominant in the presence of accretion outflows, for the fan beam emission of the accretion column of the neutron stars in PULXs. We show that the three nearby PULXs (RX J0209.6−7427, Swift J0243.6+6124 and SMC X-3), namely the three musketeers here, have their main pulsed emission not strongly collimated even if strong outflows exist. This conclusion can be extended to the current sample of extragalactic PULXs, if accretion outflows are commonly produced from them. This means that the observed high luminosity of PULXs is indeed intrinsic, which can be used to infer the existence of very strong surface magnetic fields of ∼ 1013−14 G, possibly multipole fields. However, if strong outflows are launched from the accretion disks in PULXs as a consequence of disk spherization by radiation pressure, regular dipole magnetic fields of ∼ 1012 G may be required, comparable to that of the three musketeers, which have experienced large luminosity changes from well below their Eddington limit (2 × 1038 erg s−1 for a NS) to super-Eddington and their maximum luminosity fills the luminosity gap between Galactic pulsars and extragalactic PULXs. Copyright © 2022, The Authors. All rights reserved.

关键词： Luminance

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The maximum accreted mass of recycled pulsars

arXiv

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arXiv 2021年

作者： Li, Zhenwei Chen, Xuefei Chen, Hai-Liang Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science China University of the Chinese Academy of Science Yuquan Road 19 Shijingshan Block Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China

The maximum mass of neutron stars (NSs) is of great importance for constraining equations of state of NSs and understanding the mass gap between NSs and stellar-mass black holes. NSs in X-ray binaries would increase in mass by accreting material from their companions (known as recycling process), and the uncertainties in the accretion process give challenge to study the NS mass at birth. In this work, we investigate the NS accreted mass with considering the effect of NS spin evolution and give the maximum accreted mass for NSs in the recycling process. By exploring a series of binary evolution calculations, we obtain the final NS mass and the maximum accreted mass for a given birth mass of NS and a mass transfer efficiency. Our results show that the NSs can accrete relatively more material for binary systems with the donor masses in the range of 1.8 ∼ 2.4M☉, the NSs accrete relatively more mass when the remnant WD mass is in the range of ∼ 0.25 − 0.30M☉, and the maximum accreted mass is positively correlated with the initial NS mass. For a 1.4M☉ NS at birth with a moderate mass transfer efficiency of 0.3, the maximum accreted mass could be 0.27M☉. The results can be used to estimate the minimum birth mass for systems with massive NSs in observations. Copyright © 2021, The Authors. All rights reserved.

关键词： Mass transfer

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Pulsation Properties of Blazhko and Non-Blazhko RRab Stars

arXiv

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arXiv 2025年

作者： Zong, Peng Fu, Jian-Ning Su, Jie Zhang, Bing-Kai Liu, Gao-Chao Sun, Weichao Wang, Jiaxin Zhang, Bo Hu, Xueying Bai, Zhongrui Zong, Weikai Key Laboratory of Functional Materials and Devices for Informatics Anhui Higher Education Institutes School of Physics and Electronic Engineering Fuyang Normal University Fuyang236037 China School of Physics and Astronomy Beijing Normal University Beijing100875 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Department of Physics Fuyang Normal University Fuyang236041 China Key Laboratory of Functional Materials and Devices for Informatics Anhui Higher Education Institutes Fuyang Normal University Fuyang236037 China Center for Astronomy and Space Sciences China Three Gorges University Yichang443002 China School of Science Chongqing University of Posts and Telecommunications Chongqing400065 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories of China Chinese Academy of Science Beijing100012 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

In this study, we conduct a comparative analysis of the properties of Blazhko and non-Blazhko RRab stars. We identified 1054 non-Blazhko and 785 Blazhko RRab stars in the photometric data observed by K2 mission, which, combined with those 37 stars observed in the original Kepler field, constituted our study sample. Using the Fourier Decomposition method, we calculated the pulsation parameters, including phase differences and amplitude ratios, for these RRab stars, revealing significant discrepancies in the pulsation parameters between Blazhko and non-Blazhko RRab stars. However, distinguishing between Blazhko and Non-Blazhko RRab stars based on Fourier parameters remains challenging due to the significant overlap in their distributions. By cross-matching our sample with the LRS of LAMOST DR12, we identified 147 Blazhko and 111 non-Blazhko RRab stars, which exhibit similar metallicity distributions. Furthermore, cross-matching with Gaia DR3 data yielded 766 Blazhko and 950 non-Blazhko RRab stars, showing differences in color indices but not in absolute magnitudes. Our findings suggested the Blazhko effect is linked to pulsation parameters and colors, rather than metallicities or absolute magnitude. © 2025, CC BY-NC-SA.

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On the Origin of the Strong Optical Variability of Emission-line Galaxies

arXiv

引用

arXiv 2022年

作者： Lin, Ruqiu Zheng, Zhen-Ya Hu, Weida Jiang, Chunyan Pan, Xiang Yang, Chenwei Yuan, Fang-Ting Rahna, P.T. Wang, Jian-Guo Wang, Yibo Jiang, Ning Zhu, Shuairu Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences No. 19A Yuquan Road Beijing100049 China CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China Key Laboratory for Polar Science MNR Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

Emission-line galaxies (ELGs) are crucial in understanding the formation and evolution of galaxies, while little is known about their variability. Here we report the study on the optical variability of a sample of ELGs selected in the COSMOS field, which has narrow-band observations in two epochs separated by 12 years. This sample was observed with Suprime-Cam (SC) and Hyper Suprime-Cam (HSC) on the Subaru telescope in NB816 and i'/i bands, respectively. After carefully removing the wing effect of a narrow-band filter, we check the optical variability in a sample of 181 spectroscopically confirmed ELGs. We find that 0 (0/68) Hα emitters, 11.9% (5/42) [O iii] emitters, and 0 (0/71) [O ii] emitters show significant variability (|∆mNB| ≥ 3 σ∆mNB,AGN = 0.20 mag) in the two-epoch narrow-band observations. We investigate the presence of active galactic nucleus (AGN) in this variable ELG (var-ELG) sample with three methods, including X-ray luminosity, mid-infrared activity, and radio-excess. We find zero bright AGN in this var-ELG sample, but cannot rule out the contribution from faint AGN. We find that SNe could also dominate the variability of the var-ELG sample. The merger morphology shown in the HST/F814W images of all the var-ELG sample is in agreement with the enhancement of star formation, i.e., the SNe activity. © 2022, CC BY.

关键词： Galaxies

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The 2175 Å~ Bump Features in FeLoBAL Quasars: One Indicator of MW-like Dust in the Nuclear Region of Quasar

arXiv

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arXiv 2022年

作者： Zhang, Shaohua Ge, Jian Ji, Tuo Jiang, Peng Luo, Zhijian Pan, Xiang Shi, Xiheng Shu, Chenggang Wang, Jianguo Xiao, Hubing Zhou, Hongyan Shanghai Key Lab for Astrophysics Shanghai Normal University Shanghai200234 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China Key Laboratory of Polar Science Polar Research Institute of China Ministry of Natural Resources Shanghai200136 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Yunnan Kunming650011 China Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Chinese Academy of Sciences Anhui Hefei230026 China School of Astronomy and Space Science University of Science and Technology of China Anhui Hefei230026 China

To investigate the properties of dust in the nuclear region of quasars, we explored the extinction curves of the iron low-ionization broad absorption line (FeLoBAL) quasar SDSS J163004.29+311957.6 and its two analogues. The parameterized extinction curves indicated the Milky Way-like 2175 Å bump features in underlying extinction, which are similar to those seen in the Local Group and a subset of high-redshift star-forming galaxies. Compared to the bump features in the Large Magellanic Clouds (LMC), the detections in this work are much closer to those in the Milky Way (MW). These bump features, as well as those in the high- and low-ionization broad absorption line (BAL) quasars of Zhang et al., are probably the counterpart of the 2175 Å bump features in the quasar environment. This type of dust grain is generally small, easily disrupted by high-energy photons and has difficulty surviving in the radiation field of the active galactic nucleus (AGN). However, due to the presence of absorption-line outflows, the 2175 Å bump feature in quasars, which should be rare, is seen many times in BAL quasars. The shielding effect of outflow clouds allows the MW-like dust grains to be assembled or extends the survival period in the quasar nuclear region. The process, and physical and chemical conditions deserve further observational study and investigation. © 2022, CC BY.

关键词： Dust

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Searching for cataclysmic variable stars in unidentified X-ray sources

arXiv

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arXiv 2022年

作者： Takata, Jumpei Wang, X.F. Kong, A.K.H. Mao, J. Hou, X. Hu, C.-P. Lin, L.C.-C. Li, K.L. Hui, C.Y. Department of Astronomy School of Physics Huazhong University of Science and Technology Wuhan430074 China Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Department of Physics National Changhua University of Education Changhua50007 Taiwan Department of Physics National Cheng Kung University Tainan701401 Taiwan Department of Astronomy and Space Science Chungnam National University Daejeon305-764 Korea Republic of

We carry out a photometric search for new cataclysmic variable stars (CVs), with the goal of identification for candidates of AR Scorpii-type binary systems. We select GAIA sources that are likely associated with unidentified X-ray sources, and analyze the light curves taken by the Zwicky Transient Facility, Transiting Exoplanet Survey Satellite, and Lulin One-meter Telescope in Taiwan. We investigate eight sources as candidates for CVs, among which six sources are new identifications. Another two sources have been recognized as CVs in previous studies, but no detailed investigations have been done. We identify two eclipsing systems that are associated with an unidentified XMM-Newton or Swift source, and one promising candidate for polar associated with an unidentified ASKA source. Two polar candidates may locate in the so-called period gap of a CV, and the other six candidates have an orbital period shorter than that of the period gap. Although we do not identify a promising candidate for AR Scorpii-type binary systems, our study suggests that CV systems that have X-ray emission and do not show frequent outbursts may have been missed in previous surveys. © 2022, CC0.

关键词： Surveys

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The interaction of Type Iax supernova ejecta with a helium companion star

arXiv

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arXiv 2020年

作者： Zeng, Yaotian Zheng-Wei, Liu Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Science Beijing100012 China Center for Astronomical Mega-Science CAS Beijing100012 China

Type Iax supernovae (SNe Iax) are an important sub-luminous class of SNe Ia. However, their progenitors and explosion mechanism have not been understood yet. It has been suggested that SNe Iax may be produced from weak deflagration explosions of Chandrasekhar-mass white dwarfs (WDs) in binary systems with a helium (He) star donor. In such progenitor systems, the stripped He companion material caused by the ejecta-companion interaction is expected to present some He features in their late-time spectra. However, the detection of He lines in late-time spectra of SNe Iax has not yet been successful, which gives an upper limit on the amount of stripped He mass of . 2 × 10−3 − 0.1 M . In this work, we study the interaction between SN Iax ejecta and a He star companion by performing three-dimensional hydrodynamical simulations with a weak pure deflagration explosion model. We find that about 4 × 10−3 M of He material can be stripped off from the companion star by SN explosion, which is very close to (or lower than) the observational upper-limit on the total stripped He mass in SNe Iax. We, therefore, conclude that non-detection of He lines in late-time spectra of SNe Iax could be reasonably explained if they are indeed resulted from weak pure deflagration explosions of Chandrasekhar-mass WDs in progenitor systems with a He star donor. Copyright © 2020, The Authors. All rights reserved.

关键词： Helium

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Mass-Ratio Distribution of Binaries From the LAMOST-MRS Survey

arXiv

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arXiv 2022年

作者： Li, Jiangdan Li, Jiao Liu, Chao Li, Chunqian Guo, Yanjun Wang, Luqian Chen, Xuefei Xing, Lifeng Hou, Yonghui Han, Zhanwen 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Key Lab of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Nanjing Institute of Astronomical Optics & Technology National Astronomical Observatories Chinese Academy of Sciences Nanjing210042 China School of Astronomy and Space Science University of Chinese Academy of Sciences China

Binary evolution leads to the formation of important objects crucial to the development of astrophysics, but the statistical properties of binary populations are still poorly understood. The LAMOST-MRS has provided a large sample of stars to study the properties of binary populations, especially for the mass ratio distributions and the binary fractions. We have devised a Peak Amplitude Ratio (PAR) approach to derive the mass ratio of a binary system based on results obtained from its spectrum. By computing a cross-correlation function (CCF), we established a relationship between the derived mass ratio and the PARs of the binary systems. By utilizing spectral observations obtained from LAMSOT DR6 DR7, we applied the PAR approach to form distributions of the derived mass ratio of the binary systems to the spectral types. We selected the mass ratio within the range of 0.6 − 1.0 for investigating the mass-ratio distribution. Through a power-law fitting, we obtained the power index γ values of −0.42 ±0.27, 0.03 ±0.12, and 2.12 ±0.19 for A-, F-, and G-type stars identified in the sample, respectively. The derived γ-values display an increasing trend toward lower primary star masses, and G-type binaries tend to be more in twins. The close binary fractions (for P 150 d and q 0.6) in our sample for A, F and G binaries are 7.6 ± 0.5%, 4.9 ± 0.2% and 3.7 ± 0.1%, respectively. Note that the PAR approach can be applied to large spectroscopic surveys of stars. Copyright © 2022, The Authors. All rights reserved.

关键词： Surveys

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Distinguishing super-Nyquist frequencies via their temporal variation in γ Doradus stars from continuous photometry

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Astronomy and Astrophysics 2025年 693卷

作者： Wang, Xuan Zong, Weikai Ma, Xiao-Yu Charpinet, Stéphane Wu, Tao Wang, Haotian Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China School of Physics and Astronomy Beijing Normal University Beijing100875 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Institute Université de Liège Allée du 6 Août 19C Liège4000 Belgium IRAP CNRS UPS CNES Université de Toulouse 14 Av. Edouard Belin Toulouse31400 France 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 University of Chinese Academy of Sciences Beijing100049 China Institute of Astronomy KU Leuven Celestijnenlaan 200D Leuven3001 Belgium

Given their tendency to mix in with real pulsations, the reflection of super-Nyquist frequencies (SNFs) pose a threat to asteroseismic properties. Although SNFs have been studied in several pulsating stars, a systematic survey remains to be explored. Here, we propose a method for identifying SNFs from Kepler and TESS photometry by characterizing their periodic frequency modulations using a sliding Fourier transform. After analyzing long-cadence photometry in the Kepler legacy, we identified 304 SNFs in 56 stars from 45 607 frequencies in ∼600 γ Doradus stars, corresponding to a fraction of approximately 0.67% and 9.2%, respectively. Most SNFs were detected in the frequency range of pressure mode over 120 μHz and the fraction of SNF detection increases as frequency up to ∼7%. We found only two potential SNFs mixed with gravity modes in two γ Doradus stars. These findings indicate that SNFs have a negligible impact on global seismic properties, such as those derived from period spacing in γ Doradus stars. However, we stress that SNFs must be carefully and systematically examined by this method in other pulsating stars, particularly δ Scuti and hot B subdwarf stars, to establish a solid foundation for the precise asteroseismolgy of various types of pulsators. © The Authors 2025.

关键词： Stars

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