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arXiv 2024年

作者： Zong, Peng Fu, Jian-Ning Su, Jie Hu, Xueying Zhang, Bo Wang, Jiaxin Liu, Gao-Chao Meng, Gang Catanzaro, Gianni Frasca, Antonio Wang, Haotian Zong, Weikai Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Department of Astronomy Beijing Normal University Beijing100875 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 National Astronomical Observatories of China Chinese Academy of Science Beijing100012 China College of Science Chongqing University of Posts and Telecommunications Chongqing400065 China Center for Astronomy and Space Sciences China Three Gorges University Yichang443002 China INAF - Osservatorio Astrofisico di Catania Via S.Sofia 78 CataniaI-95123 Italy

We conduct an asteroseismological analysis on the non-Blazhko ab-type RR Lyrae star EPIC 248846335 employing the Radial Stellar Pulsations (RSP) module of the Modules for Experiments in Stellar Astrophysics (MESA) based on the set of stellar parameters. The atmospheric parameters as Teff = 6933±70 K, log g = 3.35± 0.50 and [Fe/H] = -1.18 ± 0.14 are estimated from the Low-Resolution Spectra of LAMOST DR9. The luminosity L = 49.70+2.99−1.80 L and mass M = 0.56 ± 0.07 M are calculated, respectively, using the distance provided by Gaia and the metallicity estimated from the Low-Resolution Spectra. The Fourier parameters of the light curves observed by K2 and RV curves determined from the Medium-Resolution Spectra of LAMOST DR10 are also calculated in this work. The period of the fundamental mode of the star and the residuals r of the Fourier parameters between the models and observations serve to select optimal model, whose stellar parameters are Teff = 6700 ± 220 K, log g = 2.70, [Fe/H] = -1.20 ± 0.2, M = 0.59 ± 0.05 M, and L = 56.0 ± 4.2 L. The projection factors are constrained as 1.20 ± 0.02 and 1.59 ± 0.13 by the blue- and red-arm observed velocities with their corresponding RV curves derived from the best-fit model, respectively. The precise determination of stellar parameters in ab-type RR Lyrae stars is crucial for understanding the physical processes that occur during pulsation and for providing a deeper understanding of its Period-Luminosity relationship. © 2024, CC BY-NC-SA.

关键词： Stars

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Fan beamed X-ray emission from 1 keV to above 130 keV from the ultraluminous X-ray pulsar RX J0209.6−7427 in the Small Magellanic Cloud

arXiv

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arXiv 2022年

作者： Hou, Xian Ge, M.Y. Ji, L. Zhang, S.N. You, Y. Tao, L. Zhang, S. Soria, R. 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 School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China Department of Astronomy Tsinghua University Beijing100084 China

We present detailed timing and spectral analyses of the transient X-ray pulsar RX J0209.6−7427 in the Small Magellanic Cloud during its 2019 giant outburst. With a better known distance than most galactic X-ray pulsars, its peak luminosity is determined to be (1.11 ± 0.06) × 1039 erg s−1;it is thus a bonda fide pulsating ultraluminous X-ray source (PULX). Owing to the broad energy band of Insight-HXMT, its pulsed X-ray emission was detected from 1 keV up to the 130−180 keV band, which is the highest energy emission detected from any PULXs outside the Milky Way. This allows us to conclude that its main pulsed X-ray emission is from the "fan beam" of the accretion column, and its luminosity is thus intrinsic. We also estimate its magnetic field of (4.8−8.6)×1012 G or (1.7−2.2)×1013 G, from its spin evolution or transition in the accretion column structure during the outburst;we suggest that the two values of the magnetic field strength correspond to the dipole and multipole magnetic fields of the neutron star, similar to the recent discovery in the Galactic PULX Swift J0243.6+6124. Therefore, the nature of the neutron star and its ULX emission can be understood within the current theoretical frame of accreting neutron stars. This may have implications for understanding the nature of those farther away extragalactic PULXs. Copyright © 2022, The Authors. All rights reserved.

关键词： Luminance

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Magnetic topologies of two weak-line T Tauri stars TAP 4 and TAP 40

arXiv

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arXiv 2023年

作者： Xiang, Yue Gu, Shenghong Donati, J.-F. Hussain, G.A.J. Cameron, A. Collier 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 Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China IRAP Université de Toulouse CNRS UPS CNES ToulouseF-31400 France Keplerlaan 1 NoordwijkNL-2201AZ Netherlands School of Physics and Astronomy University of St Andrews Fife KY16 9SS United Kingdom

We present a Zeeman-Doppler imaging study of two weak-line T Tauri stars TAP 4 and TAP 40, based on the high-resolution spectropolarimetric observations with ESPaDOnS at the Canada-France-Hawaii Telescope in November 2013, in the framework of the MaTYSSE large programme. We apply two Zeeman-Doppler imaging codes to the Stokes I and V profiles to reconstruct their brightness and large-scale magnetic field images. The results given by the two imaging codes are in good agreement with each other. TAP 4 shows a large polar cool spot and several intermediate-latitude warm spots on its surface, whereas TAP 40 exhibits very weak variations in its Stokes I profiles suggesting a mostly unspotted photosphere. We detect Zeeman signatures in the Stokes V profiles of both stars. The reconstructed magnetic maps reveal dominantly toroidal fields, which enclose about 60 per cent of the total magnetic energy for both of TAP 4 and TAP 40. Both stars show prominent circular ring features of the azimuthal magnetic field. We derive a solar-like surface differential rotation on TAP 4 from the tomographic modelling. The brightness image of TAP 4 is used to predict the radial velocity jitters induced by its activity. After filtering out the activity jitter, the RMS of its RVs is reduced from 1.7 km s−1 to 0.2 km s−1, but we do not detect any periodic signals in the filtered RVs of TAP 4, implying that it is unlikely to host a close-in exoplanet more massive than ∼3.5 MJup at 0.1 au. Copyright © 2023, The Authors. All rights reserved.

关键词： Luminance

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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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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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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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The Common Envelope evolution Outcome. II. Short Orbital Period Hot Subdwarf B Binaries Reveal a Clear Picture

arXiv

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arXiv 2023年

作者： Ge, Hongwei Tout, Christopher A. Webbink, Ronald F. Chen, Xuefei Sarkar, Arnab Li, Jiao Li, Zhenwei Zhang, Lifu Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District 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 Institute of Astronomy The Observatories University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom University of Illinois at Urbana-Champaign 1002 W Green St Urbana61801 United States Key Lab of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China University of Chinese Academy of Sciences Beijing100049 China

Common envelope evolution (CEE) is vital to form short orbital period compact binaries. It covers many objects, such as double compact merging binaries, type Ia supernovae progenitors, binary pulsars and X-ray binaries. Knowledge of the common envelope (CE) ejection efficiency still needs to be improved, though progress has been made recently. Short orbital period hot subdwarf B star (sdB) plus white dwarf (WD) binaries are the most straightforward samples with which to constrain CEE physics. We apply the known orbital period–white dwarf mass relation to constrain the sdB progenitors of seven sdB+WD binaries with a known inclination angle. The average CE efficiency parameter is 0.32. This is consistent with previous studies. However, the CE efficiency need not be constant but a function of the initial mass ratio based on well-constrained sdB progenitor mass and evolutionary stage. Our results can be used as physical inputs for binary population synthesis simulations of related objects. A similar method can also be applied to study other short orbital period WD binaries. Copyright © 2023, The Authors. All rights reserved.

关键词： White dwarfs

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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

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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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