检索结果-内蒙古大学图书馆

Orbital period correction and light curve modeling of the W-subtype shallow contact binary OW Leo

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第2期21卷 24-30页

作者： Xiao Zhou Sheng-Bang Qian Yunnan Observatories Chinese Academy of Sciences(CAS)Kunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of the Chinese Academy of Sciences Beijing 100049China

Orbital period and multi-color light curves’investigation of OW Leo are presented for the first *** orbital period of OW Leo is corrected from P=0.325545 days to P=0.32554052 days in our work,and the observational data from the All-Sky Automated Survey for Super Novae(ASAS-SN)are used to test the newly determined orbital ***,the phased light curves are calculated with the new period and the Wilson-Devinney program is applied to model the light curves,which reveal that OW Leo is a W-subtype shallow contact binary system(q=3.05,f=12.8%).The absolute physical parameters of the two component stars are estimated to be M_(1)=0.31(1)M_(⊙),M_(2)=0.95(3)M_(⊙),R_(1)=0.63(1)R⊙,R_(2)=1.04(1)R_(⊙),L_(1)=0.43(1)L_(⊙)and L_(2)=1.01(2)L_(⊙).The evolutionary status shows that the more massive star is less evolved than the less massive *** Leo has very low metal abundance,which means its formation and evolution are hardly influenced by any additional *** is formed from an initially detached binary system through nuclear evolution and angular momentum loss via magnetic braking,and has passed a very long time of main sequence evolution.

关键词： techniques photometric-binaries eclipsing-stars evolution

Binary Stars in the New Millennium

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Xuefei, Chen Zhengwei, Liu Zhanwen, Han Yunnan Observatories The Chinese Academy of Sciences Kunming650296 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

Binary stars are as common as single stars. Binary stars are of immense importance to astrophysicists because that they allow us to determine the masses of the stars independent of their distances. They are the cornerstone of the understanding of stellar evolutionary theory and play an essential role in cosmic distance measurement, galactic evolution, nucleosynthesis and the formation of important objects such as cataclysmic variable stars, X-ray binaries, Type Ia supernovae, and gravitational wave-producing double compact objects. In this article, we review the significant theoretical and observational progresses in addressing binary stars in the new millennium. Increasing large survey projects have led to the discovery of enormous numbers of binary stars, which enables us to conduct statistical studies of binary populations, and therefore provide unprecedented insight into the stellar and binary evolution physics. Meanwhile, the rapid development of theoretical concepts and numerical approaches for binary evolution have made a substantial progress on the alleviation of some long-standing binary-related problems such as the stability of mass transfer and common envelope evolution. Nevertheless, it remains a challenge to have a full understanding of fundamental problems of stellar and binary astrophysics. The upcoming massive survey projects and increasingly sophisticated computational methods will lead to future progress. © 2023, CC BY.

关键词： Mass transfer

On the surface helium abundance of B-type hot subdwarf stars from the WD+MS channel of Type Ia supernovae

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Ji, Rui-Jie Meng, Xiang-Cun Liu, Zheng-Wei Yunnan Observatories Chinese Academy of Sciences Kunming 650216 Kunming650216 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 Yunnan Key Laboratory Kunming650216 China

The origin of intermediate helium (He)-rich hot subdwarfs are still unclear. Previous studies have suggested that some surviving Type Ia supernovae (SNe Ia) companions from the white dwarf + main-sequence (WD+MS) channel may contribute to the intermediate He-rich hot subdwarfs. However, previous studies ignored the impact of atomic diffusion on the post-explosion evolution of surviving companion stars of SNe Ia, leading to that they could not explain the observed surface He abundance of intermediate He-rich hot subdwarfs. In this work, by taking the atomic diffusion and stellar wind into account, we trace the surviving companions of SNe Ia from the WD+MS channel using the one-dimensional stellar evolution code MESA until they evolve into hot subdwarfs. We find that the surface He-abundances of our surviving companion models during their core He-burning phases are in a range of −1 log(NHe/NH) 0, which are consistent with those observed in intermediate He-rich hot subdwarfs. This seems to further support that surviving companions of SNe Ia in the WD+MS channel are possible to form some intermediate He-rich hot subdwarfs. Copyright © 2024, The Authors. All rights reserved.

关键词： Helium

Compact objects in close orbits as gravitational wave sources: Formation scenarios and properties

学校读者我要写书评

暂无评论

Results in Physics 2024年 59卷

作者： Li, Zhenwei Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science Kunming 650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming 650216 China

Gravitational Waves (GWs) provide a unique way to explore our Universe. The ongoing ground-based detectors, e.g., LIGO, Virgo, and KAGRA, and the upcoming next-generation detectors, e.g., Cosmic Explorer and Einstein Telescope, as well as the future space-borne GW antennas, e.g., LISA, TianQin, and TaiJi, cover a wide range of GW frequencies from ∼10⁻⁴Hz to ∼10³Hz and almost all types of compact objects in close orbits serve as the potential target sources for these GW detectors. The synergistic multi-band GW and EM observations would allow us to study fundamental physics from stars to cosmology. The formation of stellar GW sources has been extensively explored in recent years, and progress on physical processes in binary interaction has been made as well. Furthermore, some studies have shown that the progress in binary evolution may significantly affect the properties of the stellar GW sources. In this article, we review the formation channels of compact objects in close orbits and discuss their implications for GW observations. © 2024 The Author(s)

关键词： Binary black holes Binary evolution Binary neutron stars Double white dwarfs Gravitational wave

Observational properties of 155 O- and B-type massive pulsating stars

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Shi, Xiang-Dong Qian, Sheng-Bang Zhu, Li-Ying Liu, Liang Li, Lin-Jia Zang, Lei P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Key Laboratory of the Structure and Evolution of Celestial Objects CAS Kunming650216 China

The O- and B-type (OB-type) pulsating stars are important objects to study the structure and evolution of massive stars through asteroseismology. A large amount of data from various sky surveys provide an unprecedented opportunity to search for and study this kind of variable star. We identify 155 OB-type pulsating stars or candidates, including 38 Oe/Be stars or candidates, from the data observed by TESS, LAMOST, and GAIA, which are almost new. Among the 155 objects, 87 samples are identified as SPB stars including 37 objects with pure low-frequency and 50 objects with both low- and high-frequency pulsation, and 14 samples are identified as BCEP stars with both low- and high-frequency pulsation. The H-R diagram shows that these SPB and BCEP stars are mainly located in their instability regions and in the evolutionary stage of the main-sequence with a mass range of 2.5-20 M☉ and 7-20 M☉. Two special objects show fourier spectra similar to BCEP stars but with different positions in H-R, Period-Temperature (P-T), and Period-Luminosity (P-L) diagrams. Meanwhile, 52 other targets are identified as candidates of OB-type pulsating stars. We also derive the preliminary results of the P-L relation for SPB and BCEP stars, respectively. This work also indicates that in addition to the H-R diagram, P-T and P-L diagrams are also very useful for the classification of SPB and BCEP. Further detailed analysis of these objects can dramatically increase our understanding of theories of evolution and structure for massive OB-type pulsating stars. © 2024, CC BY.

关键词： Giant stars

Unveiling the Nature of Gravitational-Wave Emission in Core-collapse Supernovae with Perturbative Analysis

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Zha, Shuai Andersen, Oliver Eggenberger O’Connor, Evan P. 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

Gravitational waves (GWs) can provide crucial information about the central engines of core-collapse supernovae (CCSNe). In order to unveil the nature of GW emission in CCSNe, we apply perturbative analyses with the same underlying equations as simulations to diagnose oscillations of the proto-neutron star (PNS) during ∼1 s postbounce. In the pseudo-Newtonian case, we find that radial profiles of GW emission match well between the perturbative analysis with l = 2 and simulations inside the PNS at any frequency and time. This confirms that the GW emission of CCSNe arises from the global PNS oscillations in the perturbative regime. Based on this, we solve for the discrete eigenmodes with a free PNS surface and tentatively identify a set of g modes and the f mode contributing to the peak GW emission. We also offer a possible explanation for the power gap in the GW spectrum found in simulations that lies at the frequency with vanishing cumulative emission of the PNS. Our results enhance the predictive power of perturbative analyses in the GW signals of CCSNe. Copyright © 2024, The Authors. All rights reserved.

关键词： Gravity waves

Probing diversity of type II supernovae with the Chinese Space Station Telescope

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Lin, Han Zhang, Jujia Zhang, Xinghan Yunnan Observatories Chinese Academy of Science Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science Kunming650216 China School of Physics and Information Engineering Jiangsu Second Normal University Jiangsu Nanjing211200 China

Type II supernovae (SNe II), which show abundant hydrogen in their spectra, belong to a class of SNe with diverse observed properties. It is commonly accepted that SNe II are produced by core collapse and explosion of massive stars. However, the large photometric and spectroscopic diversity of SNe II, and the mechanisms responsible for these diversities, have not been thoroughly understood. In this review, we first briefly introduce the optical characteristics and possible progenitors of each subtype of SNe II. We then highlight the role of the Chinese Space Station Telescope in future SN studies. With a deep limiting magnitude, the main survey project could detect SN IIP-like objects as distant as z ∼ 1.2, and obtain UV-optical follow-up for peculiar transients, especially those long-lived events. With a high resolution and a large field of view, the main survey camera is powerful in linking a nearby SN with its progenitor, while the integral field spectrograph is powerful in revealing the SN environment. All this information has the potential to help enrich our understanding of supernova physics. Copyright © 2024, The Authors. All rights reserved.

关键词： Space stations

Long-term double synchronization in close-in gas giant planets

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Guo, Shuaishuai Guo, Jianheng Su, Jie Yan, Dongdong Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650011 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650011 China

Hot Jupiters, orbiting their host stars at extremely close distances, undergo tidal evolution, with some being engulfed by their stars due to angular momentum exchanges induced by tidal forces. However, achieving double synchronization can prolong their survival. Using the MESA stellar evolution code, combined with the magnetic braking model of Matt et al. (2015), we calculate 25,000 models with different metallicity and study how to attain the conditions that trigger the long-term double synchronization. Our results indicate that massive planets orbiting stars with lower convective turnover time are easier to achieve long-term double synchronization. The rotation angular velocity at the equilibrium point (Ωsta) is almost equal to orbital angular velocity of planet (n) for the majority of the main sequence lifetime if a system has undergone a long-term double synchronization, regardless of their state at this moment. We further compared our results with known parameters of giant planetary systems and found that those systems with larger planetary masses and lower convective turnover time seem to be less sensitive to changes in the tidal quality factor Q'*. We suggest that for systems that fall on the state of Ωsta ≈ n, regardless of their current state, the synchronization will persist for a long time if orbital synchronization occurs at any stage of their evolution. Our results can be applied to estimate whether a system has experienced long-term double synchronization in the past or may experience it in the future. Copyright © 2024, The Authors. All rights reserved.

关键词： Synchronization

Resolution enhancement of SOHO/MDI Magnetograms

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Qin, Ying Ji, Kai-Fan Liu, Hui Yu, Xiao-Guang Yunan Observatories Chinese Academy of Sciences Yunan Kunming650011 China University of Chinese Academy of Sciences Beijing100049 China Yunnan Key Laboratory of Solar Physics and Space Science 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

Research on the solar magnetic field and its effects on solar dynamo mechanisms and space weather events has benefited from the continual improvements in instrument resolution and measurement frequency. The augmentation and assimilation of historical observational data timelines also play a significant role in understanding the patterns of solar magnetic field variation. Within the realm of astronomical data processing, super-resolution reconstruction refers to the process of using a substantial corpus of training data to learn the nonlinear mapping between low-resolution and high-resolution images, thereby achieving higher-resolution astronomical images. This paper is an application study in high-dimensional non-linear regression. Deep learning models were employed to perform super-resolution (SR) modeling on SOHO/MDI magnetograms and SDO/HMI magnetograms, thus reliably achieving resolution enhancement of full-disk SOHO/MDI magnetograms and enhancing the image resolution to obtain more detailed information. For this study, a dataset comprising 9,717 pairs of data from April 2010 to February 2011 was used as the training set, 1,332 pairs from March 2011 were used as the validation set, and 1,034 pairs from April 2011 were used as the test set. After data preprocessing, we randomly cropped 128x128 sub-images as the low resolution (LR) from the full-disk MDI magnetograms, and the corresponding 512x512 sub-images as high resolution (HR) from the HMI full-disk magnetograms for model training. The tests conducted have shown that the study successfully produced reliable 4x super-resolution reconstruction of full-disk MDI magnetograms. The MESR model’s results (0.911) were highly correlated with the target HMI magnetographs as indicated by the correlation coefficient values. Furthermore, the method achieved the best PSNR, SSIM, MAE and RMSE values, indicating that the MESR model can effectively reconstruct magnetog. © 2024, CC BY-NC-SA.

关键词： Image enhancement