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Fundamental parameters for dEB SB2 binary system J064726.39+223431.6

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arXiv 2022年

作者： Kovalev, Mikhail Wang, Song 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 M. v. Lomonosov Moscow State University Leninskie Gory Moscow119991 Russia Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We present a study of the detached eclipsing binary J064726.39+223431.6 using spectra from the LAMOST medium-resolution spectra and TESS photometry. We use full-spectrum fitting to derive radial velocities and spectral parameters: (formula presented) and (formula presented). The orbital solution and light curve analysis suggest that it is a close pair of fast rotating stars on a circular orbit. We measure their masses to be (formula presented) and their radii to be (formula presented) resulting in surface gravities of log (g) (formula presented). Theoretical models cannot match all of these properties, predicting significantly higher Teff for a given metallicity. The derived age of the system is 1.56 Gyr, which indicates that both components are younger than Sun, which contradicts to much longer orbit’s circularisation timescale. Copyright © 2022, The Authors. All rights reserved.

关键词： Stars

Jitter radiation: Towards TeV-photons of gamma-ray bursts

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arXiv 2021年

作者： Mao, Jirong Wang, Jiancheng Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650011 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 Kunming650011 China

The synchrotron mechanism has the radiation limit of about 160 MeV, and it is not possible to explain the very high energy (VHE) photons that are emitted by high-energy objects. Inverse Compton scattering as a traditional process is applied for the explanation of the VHE emission. In this paper, jitter radiation, the relativistic electron radiation in the random and small-scale magnetic field, is proposed to be a possible mechanism to produce VHE photons. The jitter radiation frequency is associated with the perturbation field. The spectral index of the jitter radiation is dominated by the kinetic turbulence. We utilize the jitter radiation to explain the gamma-ray burst (GRB 190114C and GRB 180720B) VHE emissions that were recently detected by the Imaging Atmospheric Cherenkov Telescopes (IACTs). We suggest that this mechanism can be applied to other kinds of VHE sources. © 2021, CC BY.

关键词： Stars

SN 2015bq: A luminous type ia supernova with early flux excess

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arXiv 2021年

作者： Li, Liping Zhang, Jujia Dai, Benzhong Li, Wenxiong Wang, Xiaofeng Zhai, Qian Bai, Jinming School of Physics and Astronomy Yunnan University Kunming650091 China Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel Tsinghua University Beijing100084 China

We present optical and ultraviolet (UV) observations of a luminous type Ia supernova (SN Ia) SN 2015bq characterized by the early flux excess. This SN reaches a B-band absolute magnitude at MB = −19.68 ± 0.41 mag and a peak bolometric luminosity at L = (1.75 ± 0.37) × 1043 erg s−1, with a relatively small post-maximum decline rate [∆m15(B) = 0.82 ± 0.05 mag]. The flux excess observed in the light curves of SN 2015bq a few days after the explosion, especially seen in the UV bands, might be due to the radioactive decay of 56Ni mixed into the surface. The radiation from the decay of the surface 56Ni heats the outer layer of this SN. It produces blue U − B color followed by monotonically reddening in the early phase, dominated iron-group lines, and weak intermediate-mass elements absorption features in the early spectra. The scenario of enhanced 56Ni in the surface is consistent with a large amount of 56Ni (M56Ni = 0.97 ±0.20 Mo) synthesized during the explosion. The properties of SN 2015bq are found to locate between SN 1991T and SN 1999aa, suggesting the latter two subclasses of SNe Ia may have a common origin. © 2021, CC BY.

关键词： Supernovae

Atmosphere escape inferred from modelling the Hα transmission spectrum of WASP-121B

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arXiv 2021年

作者： Yan, Dongdong Guo, Jianheng Huang, Chenliang Xing, Lei 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 Lunar and Planetary Laboratory University of Arizona TucsonAZ85721 United States

The escaping atmospheres of hydrogen driven by stellar X-ray and extreme Ultraviolet (XUV) have been detected around some exoplanets by the excess absorption of Lyα in far ultraviolet band. In the optical band the excess absorption of Hα is also found by the ground-based instruments. However, it is not certain so far if the escape of the atmosphere driven by XUV can result in such absorption. Here we present the XUV driven hydrodynamic simulation coupled with the calculation of detailed level population and the process of radiative transfer for WASP-121b. Our fiducial model predicts a mass loss rate of ∼1.28×1012g/s for WASP-121b. Due to the high temperature and Lyα intensity predicted by the fiducial model, many hydrogen atoms are populated into the first excited state. As a consequence, the transmission spectrum of Hα simulated by our model is broadly consistent with the observation. Comparing with the absorption of Hα at different observation times, the stellar XUV emission varies in the range of 0.5-1.5 times fiducial value, which may reflect the variation of the stellar activity. Finally, we find that the supersonic regions of the planetary wind contribute a prominent portion to the absorption of Hα by comparing the equivalent width of Hα, which hints that a transonic outflow of the upper atmosphere driven by XUV irradiation of the host star can be detected by the ground-based telescope and the Hα can be a good indicator of escaping atmosphere. © 2021, CC BY-NC-ND.

关键词： Hydrogen

Timing properties of the X-ray accreting pulsar RX J0440.9+4431 studied with Insight-HXMT and NICER

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arXiv 2023年

作者： Li, P.P. Tao, L. Tuo, Y.L. Ge, M.Y. Kong, L.D. Zhang, L. Bu, Q.C. Ji, L. Qu, J.L. Zhang, S. Zhang, S.N. Huang, Y. Ma, X. Ye, W.T. Zhao, Q.C. Ma, R.C. Zhao, S.J. Hou, X. Yang, Z.X. Wang, P.J. Jia, S.M. Shui, Q.C. Guan, J. Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Uinversity of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China Institut für Astronomie und Astrophysik Kepler Center for Astro and Particle Physics Eberhard Karls Universität Sand 1 TübingenD-72076 Germany School of Physics and Astronomy Sun Yat-sen University Zhuhai519082 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 School of Physics and Optoelectronic Engineering Shandong University of Technology Zibo255000 China

RX J0440.9+4431, a Be/X-ray binary, had its brightest outburst in 2022 since its discovery, with a peak X-ray flux of 2.25 Crab (as recorded by Swift/BAT, 15-50 keV). We analyze the timing properties of this giant outburst using data from Insight-HXMT and NICER, focusing on the evolution of the pulse profile and pulse fraction. We observe that when the luminosity reached around ~3 × 1037 erg s−1, a transition from double-peaked to single-peaked pulse profiles occurred across the energy range, with the peak of the low-energy profile aligning gradually with the peak of the high-energy profile. This change indicates a transition from subcritical to supercritical accretion. Additionally, we found a concave in the pulse fraction as a function of energy around 20-30 keV throughout the entire outburst period. Compared to the low luminosity, the concave becomes weaker in high luminosities, and overall, the pulse fraction is higher. We propose that this concave could be caused by the scattering of high-energy photons by the atmosphere of a neutron star, leading to a dilution of the pulse fraction. As the accretion reaches the supercritical state, the accretion column height increases, resulting in a larger direct component of strongly beamed X-ray flux, and an elevated pulse fraction. Copyright © 2023, The Authors. All rights reserved.

关键词： Luminance

Hydrodynamical simulations for the common-envelope wind model for Type Ia supernovae

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arXiv 2022年

作者： Cui, Yingzhen Meng, Xiangcun Podsiadlowski, Philipp Song, Ren Yunnan Observatories Chinese Academy of Sciences 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 Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Oxford St Edmund Hall OxfordOX1 4AR United Kingdom

Context. The single-degenerate (SD) model is one of the leading models for the progenitors of Type Ia supernovae (SNe Ia). Recently, a new version of the SD model, the common-envelope wind (CEW) model, has been proposed, which, in principle, has the potential to resolve most of the difficulties encountered by previous SD models. This model is still being developed and a number of open issues remain, such as the details of the mass-loss mechanism from the surface of the common envelope (CE), the main observational properties, and the spiral-in timescale of the binary inside the envelope. Aims. In this article, we aim to address these issues by considering hydrodynamical effects on the CE. Methods. Using the stellar evolution code MESA, we carried out a series of 1D hydrodynamical simulations of an asymptotic giant branch (AGB) star undergoing a common-envelope phase with different envelope masses (0.0007 Mo-0.06 Mo). The effect of the immersed binary was mimicked by changing the gravitational constant throughout the envelope and injecting an extra heating source at the location of the binary orbit. Results. We found that the envelopes are always dynamically unstable, leading to regular mass ejection events if the envelope is more massive than the critical value of ∼ 0.003 Mo. The κ mechanism can naturally explain this phenomenon. We also found that, due to the low mass of the CE, the estimated frictional luminosity caused by the spiral-in of the immersed binary is much less than the nuclear luminosity, and therefore will not affect the structure of the CE significantly. Conclusions. Our results imply that the CE in the CEW model cannot be very massive. We also present a rough estimate for the spiral-in timescale based on a simplified model. We found that, for reasonable assumptions, the timescale may be longer than a few 105yr;therefore, the white dwarf (WD) may have enough time to increase its mass toward the Chandrasekhar mass, avoiding a merger with the companion.

关键词： Supernovae

Photometric investigation of the eclipsing binary TX Herculis observed by LUT

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Research in Astronomy and Astrophysics 2019年第7期19卷 47-52页

作者： Li-Ying Zhu Xiao-Man Tian Xiao Zhou Lin-Jia Li Zhi-Hua Wang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China University of the Chinese Academy of Sciences Beijing 100049China

The lander of China’s Chang’E-3 spacecraft is equipped with a 15-cm telescope that is very useful for monitoring celestial objects in the ultraviolet(UV) band(245–340 nm).The Lunar-based Ultraviolet Telescope(LUT) is the first long-term lunar-based astronomical observatory,that can make uninterrupted observations of a target from the *** we present the continuous complete UV light curve of the eclipsing binary TX Herculis(TX Her).The analysis of the light curve suggests that TX Her is a detached *** dip in the light curve was explained by the emergence of a stellar dark spot on the less massive F0 type *** cyclic change of arrival eclipse times for the system reveals that it contains an additional stellar companion with a minimal mass of 0.35 M⊙ and a period of 48.92 yr,which is supported by the detected light contribution of the third body from light curve *** third body may play an important role in the formation of the present short-period system TX Her.

关键词： stars:binaries:close stars:binaries:eclipsing stars:individuals (TX Herculis) stars:multiple system stars:activity

The Spatially Resolved Properties of the GW170817 Host Galaxy

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arXiv 2023年

作者： Li, Yubin Mao, Jirong Qin, Jianbo Zheng, Xianzhong Liu, Fengshan Zhao, Yinghe Zhao, Xiaohong Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Beijing Chaoyang District100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China National Astronomical Observatories Chinese Academy of Sciences 20A Datun Road Beijing Chaoyang District100101 China

GW170817 is the unique gravitational-wave (GW) event that is associated to the electromagnetic (EM) counterpart GRB 170817A. NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A. In this paper, we particularly focus on the spatially resolved properties of NGC 4993. We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands. The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of major galaxy merger. The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion. We derive the merging rate of the compact object per galaxy by a co-evolution scenario of supermassive black hole and its host galaxy. If the galaxy formation is at redshift 1.0, the merging rate per galaxy is 3.2×10-4to 7.7×10-5within the merging decay time from 1.0 to 5.0 Gyr. The results provide the vital information for the ongoing GW EM counterpart detections. The HST data analysis presented in this paper can be also applied for the Chinese Space Station Telescope (CSST) research in the future. © 2023, CC0.

关键词： Gravity waves

On the Origin of the Strong Optical Variability of Emission-line Galaxies

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arXiv 2022年

作者： Lin, Ruqiu Zheng, Zhen-Ya Hu, Weida Jiang, Chunyan Pan, Xiang Yang, Chenwei Yuan, Fang-Ting Rahna, P.T. Wang, Jian-Guo Wang, Yibo Jiang, Ning Zhu, Shuairu Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences 80 Nandan Road Shanghai200030 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences No. 19A Yuquan Road Beijing100049 China CAS Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Anhui Hefei230026 China Key Laboratory for Polar Science MNR Polar Research Institute of China 451 Jinqiao Road Shanghai200136 China Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China

Emission-line galaxies (ELGs) are crucial in understanding the formation and evolution of galaxies, while little is known about their variability. Here we report the study on the optical variability of a sample of ELGs selected in the COSMOS field, which has narrow-band observations in two epochs separated by 12 years. This sample was observed with Suprime-Cam (SC) and Hyper Suprime-Cam (HSC) on the Subaru telescope in NB816 and i'/i bands, respectively. After carefully removing the wing effect of a narrow-band filter, we check the optical variability in a sample of 181 spectroscopically confirmed ELGs. We find that 0 (0/68) Hα emitters, 11.9% (5/42) [O iii] emitters, and 0 (0/71) [O ii] emitters show significant variability (|∆mNB| ≥ 3 σ∆mNB,AGN = 0.20 mag) in the two-epoch narrow-band observations. We investigate the presence of active galactic nucleus (AGN) in this variable ELG (var-ELG) sample with three methods, including X-ray luminosity, mid-infrared activity, and radio-excess. We find zero bright AGN in this var-ELG sample, but cannot rule out the contribution from faint AGN. We find that SNe could also dominate the variability of the var-ELG sample. The merger morphology shown in the HST/F814W images of all the var-ELG sample is in agreement with the enhancement of star formation, i.e., the SNe activity. © 2022, CC BY.

关键词： Galaxies