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arXiv 2024年

作者： Li, Xu-Zhi Zhu, Qing-Feng Ding, Xu Xu, Xiao-Hui Zheng, Hang Qiu, Jin-Sheng Liu, Ming-Chao 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 Sciences University of Science and Technology of China Hefei230026 China Deep Space Exploration Laboratory Hefei230088 China Yunnan Observatories Chinese Academy of Sciences 396 Yangfangwang Guandu District Yunnan Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P. O. Box 110 Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of the Chinese Academy of Sciences Yuquan Road 19 Shijingshan Block Beijing100049 China

Starting from more than 11,200 short-period (less than 0.5 days) EW-type eclipsing binary candidates with the All-Sky Automated Survey for Supernovae (ASAS-SN) V-band light curves, we use MCMC and neural networks (NNs) to obtain the mass ratio (q), orbital inclination (incl), fill-out factor (f) and temperature ratio (Ts/Tp). After cross-matching with the Gaia DR3 database, the final sample contains parameters of 2,399 A-type and 8,712 W-type contact binaries (CBs). We present the distributions of parameters of these 11,111 short-period CBs. The mass ratio (q) and fill-out factor (f) are found to obey log-normal distributions, and the remaining parameters obey normal distributions. There is a significant period-temperature correlation of these CBs. Additionally, the temperature ratio (Ts/Tp) tends to increase as the orbital period decreases for W-type CBs. There is no significant correlation between them for A-type CBs. The mass ratio and fill-out factor (q − f) diagram suggest there is no significant correlation between these two parameters. A clear correlation exists between the mass ratio and radius ratio. The radius ratio increases with the mass ratio. Moreover, the deep fill-out CBs tend to fall on the upper boundary of the q−Rs/Rp distribution, while the shallow fill-out CBs fall on the lower boundary. © 2024, CC BY.

关键词： Normal distribution

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Formation of ultra-massive carbon-oxygen white dwarfs from the merger of carbon-oxygen and helium white dwarf pairs

arXiv

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arXiv 2022年

作者： Wu, Chengyuan Xiong, Heran Wang, Xiaofeng Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China Tsinghua University Beijing100084 China Research School of Astronomy and Astrophysics The Australian National University CanberraACT2611 Australia Beijing Planetarium Beijing Academy of Sciences and Technology Beijing100044 China

Ultra-massive white dwarfs (UMWDs) with masses larger than 1.05Moare basically believed to harbour oxygen-neon (ONe) cores. Recently, Gaia data reveals an enhancement of UMWDs on Hertzsprung-Russell diagram (HRD), which indicates that extra cooling delay mechanism such as crystallization and elemental sedimentation may exist in the UMWDs. Further studies suggested that a portion of UMWDs should have experienced pretty long cooling delays, implying that they are carbonoxygen (CO) WDs. However, the formation mechanism of these UMCOWDs is still under debate. In this work, we investigated whether the merges of massive CO WDs with heliumWDs (HeWDs) can evolve to UMCOWDs. By employing stellar evolution codeMESA, we construct doubleWD merger remnants to investigate their final fates. We found that the post-merger evolution of the remnants are similar to R CrB stars. The helium burning of the He shell leads to the mass growing of the CO core at a rate from 2.0 × 10-6to 5.0 × 10-6Moyr-1. The final COWD mass is influenced by the wind-mass-loss rate during the post-merger evolution, and cannot exceed about 1.2Mo. The remnants with core mass larger than 1.2Mowill experience surface carbon ignition, which may finally end their lives as ONe WDs. Current results implies that at least a portion of UMWDs which experience extra long cooling delay may stem from merging of CO WDs and He WDs. © 2022, CC BY.

关键词： Merging

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Radial stellar populations of AGN-host dwarf galaxies in SDSS-IV MaNGA survey

arXiv

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arXiv 2021年

作者： Cai, Wei Zhao, Yinghe Bai, Jin-Ming Yunnan Observatories Chinese Academy of Sciences Kunming652016 China University of Chinese Academy of Sciences Beijing100049 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

Based on MaNGA integral field unit (IFU) spectroscopy we search 60 AGN candidates, which have stellar masses M? 6 5×109M and show AGN ionization signatures in the BPT diagram. For these AGN candidates, we derive the spatially resolved stellar population with the stellar population synthesis code STARLIGHT and measure the gradients of the mean stellar age and metallicity. We find that the gradients of mean stellar age (metallicity) of individual AGN-host dwarfs are diverse in 0−0.5 Re, 0.5−1 Re and 0−1 Re. However, the overall behavior of the mean stellar age (metallicity) profiles tend to be flat, as the median values of the gradients are close to zero. We further study the overall behavior of the mean stellar age (metallicity) by plotting the co-added radial profiles for the AGN sample and compare with a control sample with similar stellar mass. We find that the median values of light-weighted mean stellar ages of AGN sample are as old as 2−3 Gyr within 2 Re,which are about 4−7 times older than those of the control sample. Meanwhile, most of the AGN candidates are low-level AGNs, as only eight sources have L[O III]>1039.5 erg s−1. Hence, the AGNs in dwarf galaxies might accelerate the evolution of galaxies by accelerating the consumption of the gas, resulting in an overall quenching of the dwarf galaxies, and the AGNs also become weak due to the lack of gas. The median values of mass-weighted mean stellar age of both samples within 2 Re are similar and as old as about 10 Gyr, indicating that the stellar mass is mainly contributed by old stellar populations. The gradients of co-added mean stellar metallicity for both samples tend to be negative but close to zero, and the similar mean stellar metallicity profiles for both samples indicate that the chemical evolution of the host galaxy is not strongly influenced by the AGN. Copyright © 2021, The Authors. All rights reserved.

关键词： Galaxies

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Detection of 2460 SB2 candidates in the LAMOST-MRS, using projected rotational velocities and a binary spectral model

arXiv

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arXiv 2022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 Leninskie Gory Moscow119992 Russia Max Planck Institute for Astronomy HeidelbergD-69117 Germany Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We present a new method for the detection of double-lined spectroscopic binaries (SB2) using V sin ί values from spectral fits. The method is tested on synthetic and real spectra from LAMOST-MRS. It can reliably detect SB2 candidates for double-lined binaries with V sin ί1 + V sin ί2 −1 if the radial velocity separation is large enough. Using this method, we detect 2460 SB2 candidates, 1410 of which are new discoveries. We confirm the correlation between the radial velocity separation estimated by the binary model and V sin ί0 estimated by the single star model using the selected sample. Additionally, our method finds one new SB2 candidate in open cluster M 11. Copyright © 2022, The Authors. All rights reserved.

关键词： Stars

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evolutionary Population Synthesis model with binary stars – Yunnan-II model

引用

Proceedings of the International Astronomical Union 2020年第S341期15卷 35-38页

作者： F. Zhang Z. Han L. Li National Astronomical Observatories/Yunnan 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 email: zhangfh@***

By considering a modified version of the evolutionary population synthesis (EPS) model for stellar populations (SPs) comprising binary stars, the retrieved galaxy and HII-region parameters/properties differ from the case of neglecting binary stars. The retrieved age, stellar metallicity and mass of galaxies increase (e.g. ∼ 0.2 dex when using spectral fitting algorithm), whilst the star formation rate decreases (∼0.2 dex). The radiation fields from intermediate-age SPs with binary stars could be potentially important ionizing sources in HII regions. Under this possibility, the theoretical division between star forming galaxy and AGN on the diagnostic diagrams would move towards the up-right corner and the retrieved gaseous metallicity would *** prediction for the birth rate of binary neutron stars in SPs ranges from 10−9 to 10−6${\M {^\minus 1_\odot}} $ yr−1 when the kick velocity is from 0 to 190 km s−1.

关键词： galaxies: stellar content galaxies: fundamental parameters galaxies: evolution stars: neutron

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Comparative study of TESS photometry and radial velocities on six early K-type contact binaries with similar periods around 0.268 days

arXiv

引用

arXiv 2023年

作者： Liu, Nian-Ping Qian, S.-B. Liao, W.-P. Huang, Y. Yuan, Z.-L. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences Yuquan Road 19# Shijingshan Block Beijing100049 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China Department of Physics School of Physics and Electronics Hunan Normal University P.O. Box 110 Changsha410081 China

High-precision light curves were extracted from TESScut images. Together with APOGEE and LAMOST medium resolution spectra, a joint study was made for six early K-type contact binary candidates selected unbiasedly with orbital periods around 0.268 days. It is found that all of them (RV CVn, EK Com, V384 Ser, V1038 Her, EH CVn, and CSS J125403.7+503945) are W-subtype shallow contact systems though with different mass ratios (1/q = 0.27–0.62). The effective temperature differences between binary components are around a few hundred Kelvins. The original definition of A- and W-subtypes were compared with the customarily used methods which rely on the shape or on the photometric solutions of light curves. The latter two methods are not always reliable and therefore the radial velocity analysis is strongly recommended. Through a collection of all available K-type contact binaries with both photometric and spectroscopic measurements, it is found that almost all of them are W-subtype systems, except a few objects which have nearly identical temperatures for binary components. This W-subtype phenomenon for K-type contact binaries should be further checked with more samples in the future. Finally, the physical parameters of the targets were determined with joint data analysis and the multiplicity is discussed for these targets. V384 Ser and RV CVn are confirmed very likely to be triple systems from comprehensive analysis, while V1038 Her is a candidate of a triple system based on photometric and spectroscopic solutions. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

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Broadband multi-wavelength study of LHAASO detected AGN

arXiv

引用

arXiv 2023年

作者： Wang, Ze-Rui Xue, Rui Xiong, Dingrong Wang, Hai-Qin Sun, Lu-Ming Peng, Fang-Kun Mao, Jirong College of Physics and Electronic Engineering Qilu Normal University Jinan250200 China Department of Physics Zhejiang Normal University Jinhua321004 China 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 Department of Physics Anhui Normal University Wuhu241002 China

Recently, the Large High Altitude Air Shower Observatory (LHAASO) collaboration presented the first catalog of γ-ray sources using 508 days of LHAASO data, from March 2021 to September 2022. This catalog contains four blazars and a possible liner-type AGN counterpart. In this work, we establish averaged multi-wavelength SEDs by combining data from the Fermi-Large Area Telescope, Swift, ZTF, and WISE covering the same period as the LHAASO detection. In general, these five AGNs are found in low states at all wavelengths. To study the multi-wavelength properties of these AGNs, several jet emission models, including the one-zone leptonic model, the one-zone leptonic and hadronuclear (pp) model, the one-zone proton-synchrotron model, and the spine-layer model are applied to reproduce their averaged SEDs, respectively. We find that the one-zone leptonic model can reproduce most of the SEDs, except for the high-energy tail of the LHAASO spectra of Mrk 421 and Mrk 501. To improve the fitting, emission from pp interactions is favoured in the framework of a one-zone model. The spine-layer model, which can be treated as a multi-zone scenario, can also provide good spectral fits. The influence of different extragalactic background light models on fitting LHAASO energy spectrum is also discussed. © 2023, CC BY.

关键词： Astrophysics

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Detectability of neutrino-signal fluctuations induced by the hadron-quark phase transition in failing core-collapse supernovae

arXiv

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arXiv 2022年

作者： Lin, Zidu Zha, Shuai O'Connor, Evan P. Steiner, Andrew W. Department of Physics and Astronomy University of Tennessee Knoxville Knoxville37996 United States Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai200240 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China The Oskar Klein Centre Department of Astronomy Stockholm University AlbaNova StockholmSE-106 91 Sweden Physics Division Oak Ridge National Laboratory Oak Ridge37831 United States

We introduce a systematic and quantitative methodology for establishing the presence of neutrino oscillatory signals due to the hadron-quark phase transition (PT) in failing core-collapse supernovae from the observed neutrino event rate in water- or ice-based neutrino detectors. The methodology uses a likelihood ratio in the frequency domain as a test-statistic;it is employed for quantitative analysis of neutrino signals without assuming the frequency, amplitude, starting time, and duration of the PT-induced oscillations present in the neutrino events and thus it is suitable for analyzing neutrino signals from a wide variety of numerical simulations. We test the validity of this method by using a core-collapse simulation of a 17 solar-mass star by Zha et al. (2021) [1]. Based on this model, we further report the presence of a PT-induced oscillations quantitatively for a core-collapse supernovae out to a distance of ∼ 10 kpc, ∼ 5 kpc for IceCube and to a distance of ∼ 10 kpc, ∼ 5 kpc and ∼ 1 kpc for a 0.4 Mt mass water Cherenkov detector. This methodology will aid the investigation of a future galactic supernova and the study of hadron-quark phase in the core of core-collapse supernovae. Copyright © 2022, The Authors. All rights reserved.

关键词： Hadrons

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Convective Mixing: The Formation Channel of Li-rich Giants

arXiv

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arXiv 2024年

作者： Li, Xue-Feng Shi, Jian-Rong Li, Yan Yan, Hong-Liang Zhang, Jing-Hua Yunnan Observatories Chinese Academy of Sciences P.O.Box 110 Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing100101 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 Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China South-Western Institute for Astronomy Research Yunnan University Chenggong District Kunming650500 China

Increasing observed data indicate that part of giants has abnormally high lithium (Li) inside their surface, and their proportion is around 1%. Instead of pursuing the feasible mechanisms for extra Li enrichment, we focus on how to inhibit Li depletion from the main sequence (MS) phase of giants. With this in mind, we find that convective mixing is capable of achieving this goal and forming Li-rich giants, which is mainly attributed to the convection model with the convective boundary defined by the Ledoux criterion. Another factor in the formation of Li-rich giants in our convection models is related to the Li abundances of their progenitors. If the Li abundances of the progenitors exceed the meteoritic value (3.3 dex), then the majority of giants will be rich in Li. This is the general pattern of stellar Li abundance evolution without factoring in extra Li depletion. We propose that other Li depletion processes should also be adopted in the future, as they may be the key to the 1% puzzle. Copyright © 2024, The Authors. All rights reserved.

关键词： Mixing

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The First Photometric Analysis of Two Low Mass Ratio Contact Binary Systems In TESS Survey

arXiv

引用

arXiv 2024年

作者： Cheng, Qiyuan Xiong, Jianping Ding, Xu Ji, Kaifan Li, Jiao Liu, Chao Li, Jiangdan Luo, Jingxiao Lyu, Xin Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 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 International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories CAS Beijing100101 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Key Laboratory of Radio Astronomy and Technolgoy Chinese Academy of Sciences A20 Datun Road Chaoyang District Beijing100101 China

Low mass-ratio (q) contact binary systems are progenitors of stellar mergers such as blue straggles (BS) or fast-rotating FK Com stars. In this study, we present the first light curve analysis of two newly identified low mass-ratio contact binary systems, TIC 55007847 and TIC 63597006, that are identified from TESS. Both stars are classified as A-subtype contact binaries. We obtained the precise orbit periods for the two objects by using the O-C method, i.e. P=0.6117108 d for TIC 55007847 and P=0.7008995 d for TIC 63597006, respectively, and found an obvious periodic signal in the O-C curve of TIC 63597006. We suggest that the periodic signal comes from a third body. We further use the Markov Chain Monte Carlo (MCMC) method with PHOEBE to derive the photometric solutions for the two binaries. The photometric solution for this object shows that the contribution of the third body is about 6%. Our analysis revealed that TIC 55007847 has an extremely low mass ratio of q = 0.08. By calculating the ratio of spin angular momentum to the orbital angular momentum Js/Jo, we found that TIC 55007847 is very close to the instability threshold with Js/Jo = 0.31, indicating that it may merge into a single, fast-rotating star in the future. For TIC 63597006, q = 0.14 and Js/Jo = 0.15. This object is in a relatively stable evolutionary status at present. Copyright © 2024, The Authors. All rights reserved.

关键词： Monte Carlo methods

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