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Contact binaries at different evolutionary stages

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Research in Astronomy and Astrophysics 2020年第10期20卷 229-248页

作者： Sheng-Bang Qian Li-Ying Zhu Liang Liu Xu-Dong Zhang Xiang-Dong Shi Jia-Jia He Jia Zhang Yunnan Observatories Chinese Academy of SciencesKunming 650216China School of Physics and Astronomy Yunnan UniversityKunming 650091China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Contact binaries consist of two strongly interacting component stars where they are filling their critical Roche lobes and sharing a common *** of them are main-sequence stars,but some of them are post main-sequence *** are good astrophysical laboratories for studying several problems such as the merging of binary stars,evolution of the common envelope,the origin of luminous red nova outbursts and the formation of rapidly rotating single stars with possible planetary systems.A large number of contact binary candidates were detected by several photometric surveys around the world and many of them were observed by the LAMOST spectroscopic *** on follow-up observations,the evolutionary states and geometrical structures of some systems were understood *** this review,we will introduce and catalog new stellar atmospheric parameters(i.e.,the effective temperature(Teff),the gravitational acceleration(log(g)),metallicity([Fe/H])and radial velocity(Vr))for 9149 EW-type contact binaries that were obtained based on low-and medium-resolution spectroscopic surveys of *** we will focus on several groups of contact binary stars,i.e.,marginal contact binary systems,deep and low-mass ratio contact binary stars,binary systems below the short-period limit of contact binaries and evolved contact *** contact binaries are at the beginning of the contact stage,while deep and low-mass ratio contact binary stars are at the final evolutionary stage of tidally locked *** statistical relations including the period-temperature relation are determined well by applying LAMOST data and their formation and evolutionary states are *** period-color relation of M-type binaries reveals that there are contact binaries below the short-period *** for and investigating contact binaries near and below this limit will help us to understand the formation of contact binary systems and a new prediction for the short-period l

关键词： binaries:eclipsing stars:late-type stars:low-mass stars:formation stars:evolution

The formation of blue large-amplitude pulsators from white-dwarf main-sequence star mergers

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arXiv 2023年

作者： Zhang, Xianfei Jeffery, C. Simon Su, Jie Bi, Shaolan Institute for Frontier in Astronomy and Astrophysics Beijing Normal University Beijing102206 China Department of Astronomy Beijing Normal University Beijing100875 China Armagh Observatory and Planetarium College Hill ArmaghBT61 9DG United Kingdom 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

Blue large-amplitude pulsators (BLAPs) are hot low-mass stars which show large-amplitude light variations likely due to radial oscillations driven by iron-group opacities. Period changes provide evidence of both secular contraction and expansion amongst the class. Various formation histories have been proposed, but none are completely satisfactory. Zhang et al. (2017) proposed that the merger of a helium core white dwarf with a low-mass main-sequence star (HeWD+MS) can lead to the formation of some classes of hot subdwarf. We have analyzed these HeWD+MS merger models in more detail. Between helium-shell ignition and full helium-core burning, the models pass through the volume of luminosity – gravity– temperature space occupied by BLAPs. Periods of expansion and contraction associated with helium-shell flashes can account for the observed rates of period change. We argue that the HeWD+MS merger model provides at least one BLAP formation channel. © 2023, CC BY.

关键词： Helium

The growth history of local M 33-mass bulgeless spiral galaxies

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arXiv 2023年

作者： Kang, Xiaoyu Kudritzki, Rolf-Peter Zhang, Fenghui 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 International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China LMU München Universitätssternwarte Scheinerstr. 1 München81679 Germany Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States

NGC 7793, NGC 300, M33 and NGC 2403 are four nearby undisturbed and bulgeless low-mass spiral galaxies with similar morphology and stellar mass. They are ideal laboratories to study disc formation scenarios and stellar mass growth histories. We construct a simple chemical evolution model by assuming that discs grow gradually with continuous metal-free gas infall and metal-enriched gas outflow. By means of the classical χ2 methodology, applied to the model predictions, the best combination of free parameters capable of reproducing the corresponding present-day observations is determined, i.e. the radial dependence of the infall timescale τ = 0.1r/Rd + 3.4 Gyr (Rd is the disc scale-length) and the gas outflow efficiency bout = 0.2. The model results are in excellent agreement with the general predictions of the inside-out growth scenario for the evolution of spiral galaxies. About 80% of the stellar mass of NGC 7793 is assembled within the last 8 Gyr and 40% within the last 4 Gyr. By comparing the best-fitting model results of the three other galaxies we obtain similar results, 72% (NGC 300), 66% (NGC 2403) and 79% (M33) stellar mass were assembled within the past ∼ 8 Gyr (i.e. z = 1). These four disc galaxies simultaneously increase their sizes and stellar masses as time goes by and they grow in size at ∼ 0.30 times the rate at which they grow in mass. The scale-lengths of these four discs are now 20% – 25% larger than at z = 1. Our best-fitting model predicted the stellar mass-metallicity relation and the metallicity gradients, constrained by the observed metallicities from HII-regions emission line analysis, agree well with the observations measured from individual massive red and blue supergiant stars and population synthesis of SDSS galaxies. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

A Linear Decomposition Method to Analyze and Study Pulsar Mode Changes

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arXiv 2025年

作者： Hao, Longfei Li, Zhixuan Shen, Faxin Xu, Yonghua Huang, Yuxiang Lee, Kejia Yu, Qingzheng Wang, Hongguang 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 Astronomy School of physics Peking University Beijing100871 China National Astronomical Observatory Chinese Academy of Sciences Beijing100101 China Beijing Laser Acceleration Innovation Center Huairou Beijing101400 China Department of Astronomy Xiamen University Xiamen361005 China School of Physics and Electronic Engineering Guangzhou University Guangzhou510006 China

In this paper, we present the linear decomposition method (LDM), which we developed to detect and analyze pulsar profile variations and mode changing behaviour. We developed LDM utilizing the likelihood function approach assuming the Gaussian noise. The LDM projects pulse profiles onto significance-ordered orthonormal vector bases. We show that the method is similar to the principal component analysis (PCA), but LDM can handle more general situations. We use simulated dataset and data from the Kunming 40-m radio telescope to demonstrate the application of the LDM. We found that the LDM successfully identified mode changes for well-known mode-changing PSR B0329+54 and found a continuous pulse profile evolution for PSR B0355+54 . We also show that the LDM can be used to improve the timing precision for mode changing PSR B0329+54. Copyright © 2025, The Authors. All rights reserved.

关键词： Pulsars

Investigation into the reflection properties of the neutron star low-mass X-ray binary 4U 1636−53

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arXiv 2023年

作者： Lyu, Ming Zhang, Guobao Wang, H.G. García, Federico Department of Physics Xiangtan University Hunan Xiangtan411105 China Key Laboratory of Stars and Interstellar Medium Xiangtan University Hunan Xiangtan411105 China Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Department of Astronomy School of Physics and Materials Science Guangzhou University Guangzhou510006 China Instituto Argentino de Radioastronomía CCT La Plata CONICET CICPBA UNLP C.C.5 Villa Elisa Buenos Aires1894 Argentina

We present the spectroscopy of the neutron star low-mass X-ray binary 4U 1636-53 using six simultaneous XMM-Newton and Rossi X-ray Timing Explorer observations. We applied different self-consistent reflection models to explore the features when the disk is illuminated by either the corona or the neutron star surface. We found that the spectra could be well fitted by these two types of models, with the derived emissivity index below a typical value of 3. The relative low emissivity can be explained if the neutron star and the corona, working together as an extended illuminator, simultaneously illuminate and ionize the disk. Additionally, the derived ionization parameter in the lamppost geometry is larger than the theoretical prediction. This inconsistency likely suggests that the corona does not emit isotropically in a realistic context. Furthermore, we also found that there is a possible trend between the height of the corona and the normalization of the disk emission. This could be understood either as a variation in the reflected radiation pressure or in the context of a jet base. Finally, we found that the disk is less ionized if it is illuminated by the neutron star, indicating that the illuminating source has significant influence on the physical properties of the disk. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

Astronomical Site Monitoring System at Lijiang Observatory

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Research in Astronomy and Astrophysics 2020年第9期20卷 291-308页

作者： Yu-Xin Xin Jin-Ming Bai Bao-Li Lun Yu-Feng Fan Chuan-Jun Wang Xiao-Wei Liu Xiao Guang Yu Kai Ye Teng-Fei Song Liang Chang Shou-Sheng He Jji-Rong Mao Liang Xu Ding-Rong Xiong Xi-Liang Zhang Jian-Guo Wang Xu Ding Hai-Cheng Feng Xiang-Kun Liu Yang Huang Bing-Qiu Chen Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Sciences Chinese Academy of SciencesBeijing 100101China South-Western Institute for Astronomy Research Yunnan UiversityKunming 650500China

We installed two sets of Astronomical Site Monitoring Systems(ASMSs)at Lijiang Observatory(GMG),for the running of the 2.4-meter Lijiang optical telescope(LJT)and the 1.6-meter Multi-channel Photometric Survey Telescope(Mephisto).The Mephisto is under *** ASMS has been running on robotic mode since *** core instruments:Cloud Sensor,All-Sky Camera and AutonomousDIMM that are developed by our group,together with the commercial Meteorological Station and Sky Quality Meter,are combined into the astronomical optical site monitoring *** new Cloud Sensor's Cloud-Clear Relationship is presented for the first time,which is used to calculate the All-Sky cloud *** designed the Autonomous-DIMM located on a tower,with the same height as *** seeing data have been observed for a full ***'s data for the year 2019 are also analysed in detail,which are valuable to observers.

关键词： Astronomical Site Monitoring System Lijiang Observatory Cloud Sensor Autonomous-DIMM

Generalized split monopole magnetospheres: The effects of current sheets

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Physical Review D 2021年第2期104卷 023009-023009页

作者： Huiquan Li Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences 650216 Kunming China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences 650216 Kunming China and Center for Astronomical Mega-Science Chinese Academy of Sciences 100012 Beijing China

We show that energy should be dissipated or extracted in the current sheet (CS) of a split magnetosphere deviating from the Michel split monopole, with the CS heating up or cooling down; but the electromagnetic energy remains unchanged everywhere. Based on the decentered monopole solution generated by symmetry in flat spacetime, we construct two generalized split monopole configurations, in which the field lines intersect with the CS at arbitrary angles. One configuration resembles the outer geometry of the so-called “new pulsar magnetosphere model”, for which up to 47% of the spin down energy is transferred to the Joule heating process in the CS. In the other configuration, we observe that negative energy is dissipated in the CS, which is usually observed in magnetospheres on rotating black holes. This means that energy is extracted simultaneously from the central star and the CS to power the output Poynting flux at infinity. We interpret the extraction of energy from the CS as that thermal energy of charged particles in the CS is transferred to the ordered kinetic energy of these particles drifting in the force-free (FF) electromagnetic fields. Hence, the CS is like an “air conditioner” in the sky, which can heat up or cool down, depending on the configurations .

关键词： Neutron stars & pulsars

Photometric investigation on the W-subtype contact binary V1197 Her

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Research in Astronomy and Astrophysics 2020年第1期20卷 77-82页

作者： Xiao Zhou Boonrucksar Soonthomthum Yunnan Observatories Chinese Academy of SciencesKunming 650216China National Astronomical Research Institute of Thailand 260 Moo 4T.DonkaewA.MaerimChiangmai50180Thailand 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

Multi-color light curves of V1197 Her were obtained with the 2.4 meter optical telescope at the Thai National Observatory and the Wilson-Devinney(W-D)program was used to model the observational light *** photometric solutions reveal that V1197 Her is a W-subtype shallow contact binary system with a mass ratio of q=2.61 and a fill-out factor of f=15.7%.The temperature difference between the primary star and secondary star is only 140 K in spite of the low degree of contact,which means that V1197 Her is not only in geometrical contact configuration but is also already under thermal contact *** orbital inclination of V1197 Her is as high as i=82.7?,and the primary star is completely eclipsed at the primary *** totally eclipsing characteristic implies that the determined physical parameters are highly *** masses,radii and luminosities of the primary star(star 1)and secondary star(star2)are estimated to be M1=0.30(1)M⊙,M2=0.77(2)M⊙,R1=0.54(1)R⊙,R2=0.83(1)R⊙,L1=0.18(1)L⊙and L2=0.38(1)L⊙.The evolutionary statuses of the two component stars are drawn in the Hertzsprung-Russell diagram,showing that the less massive but hotter primary star is more evolved than the secondary *** period of V1197 Her is decreasing continuously at a rate of d P/dt=-2.58×10^-7 day·year^-1,which can be explained by mass transfer from the more massive star to the less massive one at a rate of dM2/dt=-1.61×10^-7 M⊙year^-*** light curves of V1197 Her are reported to show the O’Connell ***,a cool spot is added to the more massive star to model the asymmetry in the light curves.

关键词： techniques:photometric binaries:eclipsing stars:fundamental parameters

A new approach to constraining properties of AGN host galaxies by combining image and SED decomposition: testing upon the MBH − M✶ relation

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arXiv 2024年

作者： Yu, Haoran Fan, Lulu Han, Yunkun Sun, Weibin Zhang, Yihang Ding, Xuheng Xue, Yongquan 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 Science 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 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 International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China School of Physics and Technology Wuhan University Wuhan430072 China

The outshining light from active galactic nuclei (AGNs) poses significant challenges in studying the properties of AGN host galaxies. To address this issue, we propose a novel approach which combines image decomposition and spectral energy distribution (SED) decomposition to constrain properties of AGN host galaxies. Image decomposition allows us to disentangle optical flux into AGN and stellar components, thereby providing additional constraints on the SED models to derive more refined stellar mass. To test the viability of this approach, we obtained a sample of 24 X-ray selected type I AGNs with redshifts ranging from 0.73 to 2.47. We estimated the stellar masses for our sample and found that our results are generally consistent with earlier estimates based on different methods. Through examining the posterior distribution of stellar masses, we find that our method could derive better constrained results compared to previous SED decomposition methods. With the derived stellar masses, we further studied the MBH−M✶ relation of our sample, finding a higher intrinsic scatter in the correlation for our entire sample compared to the local quiescent correlation, which could be caused by a few "black hole monsters" in our sample. We propose that based on our method, future works could extend to larger samples of high-redshift AGN host galaxies, thereby enhancing our understanding of their properties. © 2024, CC BY.

关键词： Active Galactic Nuclei