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Spectral properties of the neutron star low-mass X-ray binary 4U 1636–53, XTE J1739–285 and MAXI J1816–195

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arXiv 2025年

作者： Fei, Zhenyan Lyu, Ming Zhang, Guobao Yang, Xuejuan 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 C.C.5 Villa Elisa1894 Argentina

We investigated simultaneous NICER plus NuSTAR observations of three neutron star low-mass X-ray binary 4U 1636–53, XTE J1739–285 and MAXI J1816–195 using the latest reflection models, with the seed photons feeding into the corona originating from either the neutron star (NS) or the accretion disk. We found that, for the sources in the hard spectral state, more than ∼ 50% of the NS photons enter into the corona if NS provides seed photons, while only ∼ 3%-5% disk photons go to the corona if seed photons come from the disk. This finding, together with the derived small height of the corona, favors the lamp-post geometry or boundary layer scenario where the corona is close to the central neutron star. Additionally, we found that the source of the seed photons has big influence in the significance of the NS radiation, especially for the soft spectral state. This result may help explain why the NS radiation in MAXI J1816–195 is weak in the previous work. More importantly, for the first time, we explored the properties of the corona in the NS systems with the compactness (l − θ) diagram. We found that the corona in the NS systems all lie in the left side of the pair-production forbidden region, away from the predicted pair-production lines. This finding indicates that either the corona in these NS systems is not pair-dominated, possibly due to the additional cooling from NS photons, or the corona is composed of both thermal and non-thermal electrons. Copyright © 2025, The Authors. All rights reserved.

关键词： Photons

A correction method for the telluric absorptions and application to Lijiang Observatory

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Research in Astronomy and Astrophysics 2021年第7期21卷 281-289页

作者： Kai-Xing Lu Zhi-Xiang Zhang Ying-Ke Huang An-Bing Ren Liang Xu Hai-Cheng Feng Yu-Xin Xin Xu Ding Xiao-Guang Yu Jin-Ming Bai Yunnan Observatories Chinese Academy of SciencesKunming 650011China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China Department of Astronomy Xiamen UniversityXiamen 361005China Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100094China Department of Astronomy China West Normal UniversityNanchong 637002China

Observing a telluric standard star for correcting the telluric absorption lines of spectrum will take a significant amount of precious telescope time,especially in the long-term spectral monitoring *** that,it is difficult to select a suitable telluric standard star near in both time and airmass to the scientific *** this paper,we present a method of correcting the telluric absorption lines by combining the advantages of long slit *** rotating the slit,we observed the scientific object and a nearby comparison star in one exposure,so that the spectra of both objects should have the same telluric transmission *** telluric transmission spectrum was constructed by dividing the observed spectrum of the comparison star by its stellar template,and was used to correct the telluric absorption lines of the scientific *** the long slit spectrograph of the Lijiang 2.4-meter telescope,we designed a long-term spectroscopic observation strategy,and finished a four-year spectroscopic monitoring for a pair of objects(an active galactic nucleus and a non-varying comparison star).We applied this method to correct the telluric absorption lines of the long-term monitored spectra by the Lijiang 2.4-meter telescope,and investigated the variation of the telluric absorptions at Lijiang *** found that the telluric absorption transparency is mainly modulated by the seasonal variability of the relative humidity,airmass and *** the scatter of the [O Ⅲ] λ5007 fluxes emitted from the narrow-line region of active galactic nuclei as an indicator,we found that the correction accuracy of the telluric absorption lines is 1%.

关键词： techniques:telluric absorption methods:data analysis techniques:spectroscopic quasars:individual(SDSS J1536+0441)

Short-period Post-Common Envelope Binaries with Balmer Emission from SDSS and LAMOST Based on ZTF Photometric Data

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arXiv 2024年

作者： Lifang, Li Fenghui, Zhang Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

We present here 55 short period PCEBs containing a hot WD and a low-mass MS. Based on the photometric data from ZTF DR19, the light curves are analyzed for about 200 WDMS binaries with emission line(s) identified from SDSS or LAMOST spectra, in which 55 WDMS binaries are found to exhibit variability in their luminosities with a short period and are thus short-period binaries (i.e. PCEBs). In addition, it is found that the orbital periods of these PCEBs locate in a range from 2.2643 to 81.1526 hours. However, only 6 short-period PCEBs are newly discovered and the orbital periods of 19 PCEBs are improved in this work. Meanwhile, it is found that three objects are newly discovered eclipsing PCEBs, and a object (i.e. SDSS J1541) might be the short-period PCEB with a late M-type star or a brown dwarf companion based on the analysis of its spectral energy distribution. At last, the mechanism(s) being responsible for the emission features in the spectra of these PCEBs are discussed, the emission features arising in their optical spectra might be caused by the stellar activity or an irradiated component owing to a hot white dwarf companion because most of them contain a white dwarf with an effective temperature higher than ∼10,000 K. © 2024, CC BY-NC-ND.

关键词： White dwarfs

Stellar Populations of AGN-host Dwarf Galaxies Selected with Different Methods

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arXiv 2024年

作者： Li, Xiejin Zhao, Yinghe Bai, Jinming Yunnan Observatories Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China A20 Datun Road Chaoyang District Beijing100101 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

In this paper we investigate the stellar populations and star formation histories of 235 active galactic nuclei (AGN)-host dwarf galaxies, consisting of four samples identified separately with different methods (i.e., radio, X-ray, mid-IR and variability), utilizing the synthesis code STARLIGHT and spectra from the Sloan Digital Sky Survey (SDSS) Data Release 8. Our results show that the variability sample is the oldest, while the mid-IR sample is the youngest, for which the luminosity at 4020 Å is dominated (> 50%) by the young population (t 8 yr). The light-weighted mean stellar age of the whole sample is in general about 0.7 dex younger than the optical sample studied in Cai et al. We compare the population results between fitting models with and without a power-law (PL) component and find that the neglect of a PL component would lead to an under- and over-estimation by 0.2 and 0.1 dex for the light- and mass-weighted mean stellar age, respectively, for our sample of dwarf galaxies, which has a mean fractional contribution of ∼16% from the AGN. In addition, we obtain further evidence for a possible suppression of star formation in the host galaxy by the central AGN. We also find that there exists an anti-correlation between the extinction-corrected [O III] luminosity and light-weighted mean stellar age, confirming our previous finding that there is a physical connection between AGN and star-forming activities in AGN-host dwarfs. © 2024, CC BY.

关键词： Active Galactic Nuclei

The C/O ratio of He-accreting carbon-oxygen white dwarfs and type Ia supernovae

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Research in Astronomy and Astrophysics 2020年第1期20卷 19-26页

作者： Xiao Cui Bo Wang Cheng-Yuan Wu Xiang-Cun Meng Zhan-Wen Han Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of the Chinese Academy of Sciences Beijing 100049China

Type Ia supernovae(SNe Ia)are thermonuclear explosions of carbon-oxygen white dwarfs(CO WDs),and are believed to be excellent cosmological distance indicators due to their high luminosity and remarkable ***,there exists a diversity among SNe Ia,and a poor understanding of the diversity hampers the improvement of the accuracy of cosmological distance *** variations of the ratios of carbon to oxygen(C/O)of WDs at explosion are suggested to contribute to the *** the canonical model of SNe Ia,a CO WD accretes matter from its companion and increases its mass till the Chandrasekhar mass limit when the WD *** this work,we studied the C/O ratio for accreting CO *** the stellar evolution code MESA,we simulated the accretion of He-rich material onto CO WDs with different initial WD masses and different mass accretion *** found that the C/O ratio varies for different *** C/O ratio of He-accreting CO WDs at explosion increases with a decreasing initial WD mass or a decreasing accretion *** various C/O ratios may,therefore,contribute to the diversity of SNe Ia.

关键词： stars:evolution supernovae:general white dwarfs

Properties of the optical component stars in X-ray binary systems

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arXiv 2023年

作者： Zhang, Jia Qian, Sheng-Bang Zhang, Guo-Bao Zhou, Xiao Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Department of Astronomy Key Laboratory of Astroparticle Physics of Yunnan Province Yunnan University Kunming650091 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China

We collected a total of 4,058 X-ray binary stars, out of which 339 stars had three atmospheric parameters for optical companions from Gaia and LAMOST, while 264 stars had masses and radii of optical companions determined using stellar evolution models. We conducted a thorough discussion on the reliability of each parameter. The statistical analysis revealed a noticeable bimodal distribution in the mass, radius, and age of the optical components. Our findings led to the proposal of a new quantitative classification criterion for X-ray binary stars. In this classification, one type is categorized as high-mass, high-temperature, and young, while the other type is classified as low-mass, low-temperature, and old, corresponding to High-Mass X-Ray Binaries (HMXBs) and Low-Mass X-Ray Binaries (LMXBs), respectively. The dividing lines were established at 11,500 K, 1.7 M☉, and 0.14 Gyr. The classification results of the three parameters showed consistency with one another in 90% of the cases and were in agreement with previous classifications in 80% of the cases. We found that the parameters of the two types had well-defined boundaries and distinct patterns. Based on our findings, we suggest that temperature is the best parameter for classification. Therefore, we propose that X-ray binary stars should be classified into high-temperature X-ray binaries (HTXBs) and low-temperature X-ray binaries (LTXBs). We believe that this classification is more convenient in practice and aligns well with physics. Copyright © 2023, The Authors. All rights reserved.

关键词： Stars

The Red Supergiant Progenitor of the Type II Supernova 2024abfl

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arXiv 2024年

作者： Luo, Jingxiao Zhang, Lifu Chen, Bing-Qiu Cheng, Qiyuan Guo, Boyang Li, Jiao Guo, Yanjun Xiong, Jianping Meng, Xiangcun Chen, Xuefei Liu, Zhengwei Han, Zhanwen Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China South-Western Institute for Astronomy Research Yunnan University Kunming650500 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

Linkage between core-collapse supernovae (SNe) and their progenitors is not fully understood and ongoing effort of searching and identifying the progenitors is needed. SN 2024abfl is a recent Type II supernova exploded in the nearby star-bursting galaxy NGC 2146, which is also the host galaxy of SN 2018zd. From archival Hubble Space Telescope (HST) data, we have found a red source (mF814W ∼ 25) near the location (angular distance ≤ 0.2") of SN 2024abfl before its explosion. With F814W and F606W photometry, we found that the properties of this source matched a typical red supergiant (RSG) moderately reddened by interstellar dust at the distance of the host galaxy. We conclude that the SN 2024abfl had an RSG progenitor with initial mass of 10M☉–16 M☉ © 2024, CC BY-NC-SA.

关键词： Supernovae

The possible equation of state of dark matter in low surface brightness galaxies

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Chinese Physics C 2021年第10期45卷 109-116页

作者： Xiaobo Gong Meirong Tang Zhaoyi Xu Yunnan Observatories Chinese Academy of SciencesKunming650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100012China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

The observed rotation curves of low surface brightness(LSB)galaxies play an essential role in studying dark matter,and indicate the existence of a central constant density dark matter ***,the cosmological N-body simulations of cold dark matter predict an inner cusped halo with a power-law mass density distribution,and cannot reproduce a central constant-density *** phenomenon is called cusp-core *** dark matter is quiescent and satisfies the condition for hydrostatic equilibrium,the equation of state can be adopted to obtain the density profile in the static and spherically symmetric *** address the cusp-core problem,we assume that the equation of state is independent of the scaling *** lower order approximation for this type of equation of state can naturally lead to a special case,i.e.,■,where p andρrepresent the pressure and density,respectively,V_(rot) depicts the rotation velocity of galaxy,andζandεare positive *** can obtain a density profile that is similar to the pseudo-isothermal halo model whenεis approximately *** obtain a more universally used model,let the equation of state include the polytropic model,i.e.■,from which we can obtain other types of density profiles,such as the profile that is nearly same as the Burkert profile,where s and ρ_(0) are positive constants.

关键词： galaxy dark matter-galaxy rotation curves

Adiabatic Mass Loss In Binary Stars. IV. Low and Intermediate Mass Helium Binary Stars

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arXiv 2024年

作者： Zhang, Lifu Ge, Hongwei Chen, Xuefei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650216 China 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

The unstable mass transfer situation in binary systems will asymptotically cause the adiabatic expansion of the donor star and finally lead to the common envelope phase. This process could happen in helium binary systems once the helium donor star fills its Roche-lobe. We have calculated the adiabatic mass loss model of naked helium stars with a mass range of 0.35 M☉ to 10 M☉, and every mass sequence evolved from the He-ZAMS to the cooling track of white dwarf or carbon ignition. In consideration of the influence of stellar wind, massive helium stars are not considered in this paper. Comparing stellar radius with the evolution of the Roche-lobe under the assumption of conservative mass transfer, we give the critical mass ratio qcrit = MHe/Maccretor as the binary stability criteria of low and intermediate-mass helium binary stars. On He-MS, the result shows 1.0 crit crit = 3. After early He-HG, the qcrit quickly increases even larger than 10 (more stable compared with widely used result qcrit = 4), which is dominated by the expansion of radiative envelope. Our result could be useful for these quick mass transfer binary systems such as AM CVns, UCXBs, and helium novae, and it could guide the binary population synthesis for the formation of special objects such as SNe Ia and GW sources. Copyright © 2024, The Authors. All rights reserved.

关键词： Helium