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arXiv 2024年

作者： Chen, Xinghao Zhang, Xiaobin Li, Yan Su, Jie Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

Based on 2-minute cadence TESS data, we investigate pulsations of TIC 65138566 and TIC 139729335 and discover them to be two new HADS stars with equally spaced g modes. We recognize the radial fundamental mode f1 = 18.3334 c/d and the first overtone f3 = 23.6429 c/d for TIC 65138566, and identify the highest peak f1 = 19.0955 c/d as the radial fundamental mode for TIC 139729335. For g modes, both stars display a regular period spacing of 2413 s. Through detailed seismological analysis, we deduce that these period spacing patterns correspond to modes with = 1. Moreover, our analysis reveals that with the increase in masses and metallicities, the star should display a higher degree of evolution to match a specific period spacing Π0. Conversely, the star should have a lower extent of evolution to match the radial fundamental mode. These two contradictory behaviors allow us to precisely obtain stellar physical parameters. TIC 65138566 and TIC 139729335 are determined to be two main sequence stars that have almost the same range of masses and metallicities, with M = 1.36 ± 0.06 M☉ and Z = 0.005 ± 0.002. The hydrogen abundance in the core of TIC 65138566 is estimated to be about 0.28, while TIC 139729335 has a slightly higher value of around 0.31. Finally, we suggest that the HADS δ Scuti-γ Doradus star TIC 308396022 is a main sequence star with M = 1.54 ± 0.08 M☉, Z = 0.007 ± 0.001, and Xc = 0.18 ± 0.02. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

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Asteroseismology of the pulsating extremely low-mass white dwarf SDSS J111215.82+111745.0: A model with p-mode pulsations consistent with the observations

arXiv

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arXiv 2022年

作者： Su, Jie Li, Yan Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

SDSS J111215.82+111745.0 is the second pulsating extremely low-mass white dwarf discovered. Two short-period pulsations, 107.56 and 134.275 s, were detected on this star, which would be the first observed pressure mode (p-mode) pulsations observed on a white dwarf. While the two potential p-modes have yet to be confirmed, they make SDSS J111215.82+111745.0 an interesting object. In this work, we analyzed the whole set of seven periods observed on SDSS J111215.82+111745.0. We adopt three independent period-spacing tests to reveal a roughly 93.4 s mean period spacing of = 1 g-modes, which gives added credence to the = 1 identifications. Then we perform asteroseismic modeling for this star, in which the H chemical profile is taken as a variable. The stellar parameters M = 0.1650 ± 0.0137 Mo and Teff = 9750 ± 560 K are determined from the best-fit model and the H/He chemical profiles are also defined. The two suspected p-modes are also well represented in the best-fit model, and both the stellar parameters and the pulsation frequencies are in good agreement with the values derived from spectroscopy. © 2022, CC BY.

关键词： White dwarfs

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Deep and low mass-ratio contact binaries and their third bodies

arXiv

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arXiv 2024年

作者： Liying, Zhu Shengbang, Qian Wenping, Liao Jia, Zhang Xiangdong, Shi Linjia, Li Fangbin, Meng Jiangjiao, Wang Azizbek, Matekov Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China School of Physics and Astronomy Yunnan University Kunming650091 China Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences 33 Astronomicheskaya str. Tashkent100052 Uzbekistan

Deep and low mass-ratio contact binaries (DLMCBs) are believed to be in the final stage of their contact phase, potentially leading to the formation of fast-rotating single stars such as FK Com-type stars and blue stragglers, as well as luminous red novae. These systems serve as an excellent laboratory for studying stellar coalescence and merging processes. Our search for DLMCBs began in 2004 and has since identified a group of such systems. Together with that collected from the literature, more than 100 DLMCBs have been detected so far. Half of them have had their periods investigated based on O-C curves. Some have shown period increases, while others have exhibited period decreases. Among them, more than half DLMCBs have cyclic variations, suggesting the possibility of the existence of a third body orbiting around the DLMCBs. Furthermore, with more data obtained extending the span of the O-C curve, more cyclic variations could be detected. The high proportion of signs of the presence of third bodies makes them an essential factor to consider when studying the merger of contact binaries. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

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A method for estimating masses of W Ursae Majoris-type binaries

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Research in Astronomy and Astrophysics 2020年第12期20卷 243-253页

作者： Li-Na Lu Jin-Zhong Liu Deng-Kai Jiang Ya-Hui Wang Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Laboratory of New Energy and Materials Xinjiang Institute of EngineeringUrumqi 830091China

Masses of W Ursae Majoris-type(W UMa) binaries play a critical role in investigating stellar dynamical evolutionary status. In this paper, we combine the PARSEC(PAdova and TRieste Stellar evolution Code) with the Roche geometric model to provide a method to determine the masses of W UMa systems. To verify the validity of this method, we compile a sample of 140 spectrum binaries from the literature, which includes 76 W-and 64 A-subtype systems with reliable physical parameters. We find that the average fractional difference and the standard deviation(σM) of the residuals for W-subtype and Asubtype approximately amount to 15.66% and 0.1218, 16.03% and 0.2094, respectively. Meanwhile, we also perform detailed analyses in accordance with the orbital period, the effective temperatures and the mass ratio. We find that the method is more applicable to determine masses for W UMa systems with low effective temperature and short period.

关键词： stars:binaries:eclipsing W Ursae Majoris(W UMa)binaries masses

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Type Ia Supernova Explosions in Binary Systems: A Review

arXiv

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arXiv 2023年

作者： Liu, Zheng-Wei Röpke, Friedrich K. Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Science Beijing100012 China Zentrum für Astronomie Universität Heidelberg Institut für Theoretische Astrophysik Philosophenweg 12 Heidelberg69120 Germany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35 Heidelberg69118 Germany

Type Ia supernovae (SNe Ia) play a key role in the fields of astrophysics and cosmology. It is widely accepted that SNe Ia arise from thermonuclear explosions of white dwarfs (WDs) in binary systems. However, there is no consensus on the fundamental aspects of the nature of SN Ia progenitors and their actual explosion mechanism. This fundamentally flaws our understanding of these important astrophysical objects. In this review, we outline the diversity of SNe Ia and the proposed progenitor models and explosion mechanisms. We discuss the recent theoretical and observational progress in addressing the SN Ia progenitor and explosion mechanism in terms of the observables at various stages of the explosion, including rates and delay times, pre-explosion companion stars, ejecta–companion interaction, early excess emission, early radio/X-ray emission from circumstellar material (CSM) interaction, surviving companion stars, late-time spectra and photometry, polarization signals, and supernova remnant properties, etc. Despite the efforts from both the theoretical and observational side, the questions of how the WDs reach an explosive state and what progenitor systems are more likely to produce SNe Ia remain open. No single published model is able to consistently explain all observational features and the full diversity of SNe Ia. This may indicate that either a new progenitor paradigm or the improvement of current models is needed if all SNe Ia arise from the same origin. An alternative scenario is that different progenitor channels and explosion mechanisms contribute to SNe Ia. In the next decade, the ongoing campaigns with the James Webb Space Telescope (JWST), Gaia and the Zwicky Transient Facility (ZTF), and upcoming extensive projects with the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) and the Square Kilometre Array (SKA) will allow us to conduct not only studies of individual SNe Ia in unprecedented detail but also systematic investigations for di

关键词： Explosions

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Timing and spectral analysis of GK Persei during the 2010 dwarf nova outburst

arXiv

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arXiv 2025年

作者： Pei, Songpeng Zhang, Xiaowan Li, Qiang Ou, Ziwei Yang, Taozhi Cai, Yongzhi School of Physics and Electrical Engineering Liupanshui Normal University Guizhou Liupanshui553004 China Qiannan Normal University for Nationalities Duyun558000 China Qiannan Key Laboratory of Radio Astronomy Guizhou Province Duyun558000 China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai201210 China Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter School of Physics Xi’an Jiaotong University Xi’an710049 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

GK Persei, an old nova and intermediate polar (IP), exhibited a dwarf nova (DN) outburst in 2010. This outburst was extensively observed by the Neil Gehrels Swift Observatory, beginning 1.95 days after the eruption and continuing until 13.9 days before the maximum of the outburst in the optical. In this paper, we present timing and spectral analyses, comparing the results with those of other outbursts. We confirm the spin modulation in the 2 − 10 keV X-ray range with a period of PWD = 351.325(9) s. Additionally, we detected spin modulation in the 0.3 − 2 keV band during the second half of the observations, a feature not seen in the 2015 and 2018 outbursts. This finding suggests that the soft X-ray emission in GK Per may originate partly near the magnetic poles and partly from a wind or circumstellar material. Copyright © 2025, The Authors. All rights reserved.

关键词： Spectrum analyzers

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Measuring the Virial Factor in SDSS DR7 AGNs with Redshifted Hβ and Hα Broad Emission Lines

arXiv

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arXiv 2024年

作者： Liu, H.T. Feng, Hai-Cheng Li, Sha-Sha Bai, J.M. Li, H.Z. 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 Physics Department Yuxi Normal University 134 Fenghuang Road Hongta District Yuxi Yunnan653100 China

Under the hypothesis of gravitational redshift induced by the central supermassive black hole, and based on line widths and shifts of redward shifted Hβ and Hα broad emission lines for more than 8000 SDSS DR7 AGNs, we measure the virial factor in determining supermassive black hole masses. The virial factor had been believed to be independent of accretion radiation pressure on gas clouds in broad-line region (BLR), and only dependent on inclination effects of BLR. The virial factor measured spans a very large range. For the vast majority of AGNs (>96%) in our samples, the virial factor is larger than f = 1 usually used in literatures. The f correction makes the percent of high-accreting AGNs decrease by about 100 times. There are positive correlations of f with the dimensionless accretion rate and Eddington ratio. The redward shifts of Hβ and Hα are mainly the gravitational origin, confirmed by a negative correlation between the redward shift and the dimensionless radius of BLR. Our results show that radiation pressure force is a significant contributor to the measured virial factor, containing the inclination effects of BLR. The usually used values of f should be corrected for high-accreting AGNs, especially high redshift quasars. The f correction increases their masses by one–two orders of magnitude, which will make it more challenging to explain the formation and growth of supermassive black holes at high redshifts. Copyright © 2024, The Authors. All rights reserved.

关键词： Active Galactic Nuclei

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The Distribution of Semi-Detached Binaries. *** Efficient Pipeline

arXiv

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arXiv 2023年

作者： Xiong, Jianping Ding, Xu Li, Jiadong Ge, Hongwei Cheng, Qiyuan Ji, Kaifan Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China Max-Planck-Institut für Astronomie Königstuhl 17 HeidelbergD-69117 Germany Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

Semi-detached binaries are in the stage of mass transfer and play a crucial role in studying mass transfer physics between interacting binaries. Large-scale time-domain surveys provide massive light curves of binary systems, while Gaia offers high-precision astrometric data. In this paper, we develop, validate, and apply a pipeline that combines the MCMC method with a forward model and DBSCAN clustering to search for semi-detached binary and estimate its inclination, relative radius, mass ratio, and temperature ratio using light curve. We train our model on the mock light curves from PHOEBE, which provides broad coverage of light curve simulations for semi-detached binaries. Applying our pipeline to TESS sectors 1-26, we have identified 77 semi-detached binary candidates. Utilizing the distance from Gaia, we determine their masses and radii with median fractional uncertainties of ∼26% and ∼7%, respectively. With the added 77 candidates, the catalog of semi-detached binaries with orbital parameters has been expanded by approximately 20%. The comparison and statistical results show that our semi-detached binary candidates align well with the compiled samples and the PARSEC model in Teff-L and M-R relations. Combined with the literature samples, comparative analysis with stability criteria for conserved mass transfer indicates that ∼ 97.4% of samples are undergoing nuclear-timescale mass transfer, and two samples (GO Cyg and TIC 454222105) are located within the limits of stability criteria for dynamical- and thermal-timescale mass transfer, which are currently undergoing thermal-timescale mass transfer. Additionally, one system (IR Lyn) is very close to the upper limit of delayed dynamical-timescale mass transfer. Copyright © 2023, The Authors. All rights reserved.

关键词： Mass transfer

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An initial analysis of a strongly-lensed QSOs candidate identified by LAMOST

arXiv

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arXiv 2023年

作者： Chen, Yanhui H. Tang, M.Y. Shu, H. Tu, H. Institute of Astrophysics Chuxiong Normal University Chuxiong675000 China School of Physics and Electronical Science Chuxiong Normal University Chuxiong675000 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China Department of Astronomy Yunnan University Key Laboratory of Astroparticle Physics of Yunnan Province Kunming650091 China Physics Department Shanghai Key Lab for Astrophysics Shanghai Normal University Shanghai200234 China

From 2011 to 2021, LAMOST has released a total of 76,167 quasar data. We try to search for gravitationally lensed QSOs by limiting coordinate differences and redshift differences of these QSOs. The name, brightness, spectrum, photometry and other information of each QSO will be visually checked carefully. Special attention should be paid to check whether there are groups of galaxies, gravitationally lensed arcs, Einstein crosses, or Einstein rings near the QSOs. Through careful selection, we select LAMOST J160603.01+290050.8 (A) and LAMOST J160602.81+290048.7 (B) as a candidate and perform an initial analysis. The component A and B are 3.36 arc seconds apart and they display blue during photometric observations. The redshift values of component A and B are 0.2% different, their Gaia g values are 1.3% different, and their ugriz values are 1.0% or less different. For the spectra covering from 3,690 Å to 9,100 Å, the emission lines of C II, Mg, H γ, O III, and H β are present for both component A and B and the ratio of flux(B) to flux(A) from LAMOST is basically a constant, around 2.2. However, no galaxies have been found between component A and B. Inada et al. identified them as binary quasars. But we accidentally find a galaxy group near the component A and B. If the center of dark matter in the galaxy group is at the center between component A and B, the component A and B are probably gravitationally lensed QSOs. We estimate that the Einstein mass is 1.46 × 1011 M and the total mass of the lens is 1.34 × 1013 M. The deflection angle is 1.97 arc seconds at positions A and B and the velocity dispersion is 261 km s−1. Theoretically, this candidate could be a pair of fold images of a strong lensing system by a galaxy group, and we will investigate the possibility when the redshifts of nearby galaxies are available. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

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Exploring the convective core of the high-amplitude δ Scuti star TIC 120857354 with asteroseismology

arXiv

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arXiv 2024年

作者： Chen, Xinghao Zhang, Xiaobin Li, Yan Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

Based on 2-minute cadence TESS data, 20 confident independent frequencies were identified for the star TIC 120857354. The Kolmogorov-Smirnov test reveals a rotational splitting of 2.40 μHz and a uniform frequency spacing of 74.6 μHz. Subsequently, five sets of rotational splittings were discerned, including a quintuplet and four pairs of doublets, aligning with the characteristics of p-mode rotational splitting. Based on the sets of rotational splittings and the uniform frequency spacing, we finally identified 4 radial modes, 6 dipole modes, and 10 quadrupole modes. Furthermore, we found that the frequency separations within the = 2 sequences show a decreasing trend towards lower-order modes, analogous to the = 0 sequences. A grid of theoretical models were computed to match the identified frequencies, revealing that TIC 120857354 is a main-sequence star with M = 1.54 ± 0.04 M☉, Z = 0.015 ± 0.003, Teff = 7441 ± 370 K, log g = 4.27 ± 0.01, R = 1.52 ± 0.01 R☉, L = 6.33 ± 1.53 L☉, age = 0.53 ± 0.07 Gyr, and Xc/X0 = 0.84 ± 0.05. In-depth analyses suggest that = 2 may be p-dominated mixed modes with pronounced g-mode characteristics, enabling us to probe deeper into interiors of the star and determine the relative size of the convective core to be Rc/R = 0.092 ± 0.002. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

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