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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

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

Multiwavelength Properties of Infrared-Faint Radio Sources Based on Spectral Energy Distribution Analysis

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arXiv 2024年

作者： Zhang, Yihang Fan, Lulu An, Tao Yang, Jun Sun, Weibin Yu, Haoran Han, Yunkun 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 Key Laboratory of Radio Astronomy Shanghai Astronomical Observatory 80 Nandan Road Shanghai200030 China Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory OnsalaSE-439 92 Sweden 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

Infrared-faint radio sources (IFRSs) are believed to be a rare class of radio-loud active galactic nuclei (RL AGN) characterized by their high radio-to-infrared flux density ratios of up to several thousands. Previous studies have shown that a fraction of IFRSs are likely to be hosted in dust-obscured galaxies (DOGs). In this paper, our aim was to probe the dust properties, star formation rate (SFR), and AGN activity of IFRSs by modeling the UV-to-infrared spectral energy distribution (SED) of 20 IFRSs with spectroscopic redshifts ranging from 1.2 to 3.7. We compare the Bayesian evidence of a three-component model (stellar, AGN and cold dust) with that of a two-component model (stellar and cold dust) for six IFRSs in our sample with far-infrared (FIR) photometry and find that the three-component model has significantly higher Bayesian evidence, suggesting that IFRSs are most likely to be AGN. The median SED of our IFRS sample shows similarities to AGN-starburst composite in the IR regime. The derived IR luminosities of IFRSs indicate that they are low-luminosity counterparts of high-redshift radio galaxies. We disentangle the contributions of AGN-heated and star-formation-heated dust to the IR luminosity of IFRSs and find that our sample is likely AGN-dominated. However, despite the evidence for significant impact of AGN on the host galaxy, the AGN luminosity of our sample does not show correlation with the SFR of the sources. © 2024, CC BY.

关键词： Stars

BayeSED-GALAXIES I. Performance test for simultaneous photometric redshift and stellar population parameter estimation of galaxies in the CSST wide-field multiband imaging survey

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arXiv 2023年

作者： Han, Yunkun Fan, Lulu Zheng, Xian Zhong Bai, Jin-Ming Han, Zhanwen 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 Deep Space Exploration Laboratory 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 Purple Mountain Observatory Chinese Academy of Sciences 10 Yuanhua Road Nanjing210023 China

The forthcoming CSST wide-field multiband imaging survey will produce seven-band photometric spectral energy distributions (SEDs) for billions of galaxies. The effective extraction of astronomical information from these massive datasets of SEDs relies on the techniques of both SED synthesis (or modeling) and analysis (or fitting). We evaluate the performance of the latest version of BayeSED code combined with SED models with increasing complexity for simultaneously determining the photometric redshifts and stellar population parameters of galaxies in this survey. By using an empirical statistics-based mock galaxy sample without SED modeling errors, we show finding that the random observational errors in photometries are more important sources of errors than the parameter degeneracies and Bayesian analysis method and tool. By using a Horizon-AGN hydrodynamical simulation-based mock galaxy sample with SED modeling errors about the star formation histories (SFHs) and dust attenuation laws (DALs), the simple typical assumptions lead to significantly worse parameter estimation with CSST photometries *** SED models with more flexible (or complicated) forms of SFH/DAL do not necessarily lead to better estimation of redshift and stellar population parameters. We discuss the selection of the best SED model by means of Bayesian model comparison in different surveys. Our results reveal that the Bayesian model comparison with Bayesian evidence may favor SED models with different complexities when using photometries from different surveys. Meanwhile, the SED model with the largest Bayesian evidence tends to give the best performance of parameter estimation, which is more clear for photometries with larger discriminative power. Copyright © 2023, The Authors. All rights reserved.

关键词： Galaxies

Timing analysis of EXO 2030+375 during its 2021 giant outburst observed with Insight-HXMT

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arXiv 2023年

作者： Fu, Yu-Cong Song, L.M. Ding, G.Q. Ge, M.Y. Tuo, Y.L. Zhang, S. Zhang, S.N. Hou, X. Qu, J.L. Zhang, J. Zhang, L. Bu, Q.C. Huang, Y. Ma, X. Zhou, X. Yan, W.M. Yang, Z.X. Lu, X.F. Li, T.M. Xu, Y.C. Wang, P.J. Xiao, S.H. Liu, H.X. Ren, X.Q. Du, Y.F. Zhao, Q.X. Xiao, Y.X. Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi Xinjiang830011 China University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100049 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 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 Institut für Astronomie und Astrophysik Kepler Center for Astro and Particle Physics Eberhard Karls Universität Sand 1 Tübingen72076 Germany Key Laboratory of Radio Astronomy Chinese Academy of Sciences Nanjing210008 China Xinjiang Key Laboratory of Radio Astrophysics Urumqi830011 China

We report the evolution of the X-ray pulsations of EXO 2030+375 during its 2021 outburst using the observations from Insight-HXMT. Based on the accretion torque model, we study the correlation between the spin frequency derivatives and the luminosity. Pulsations can be detected in the energy band of 1–160 keV. The pulse profile evolves significantly with luminosity during the outburst, leading to that the whole outburst can be divided into several parts with different characteristics. The evolution of the pulse profile reveals the transition between the super-critical (fan-beam dominated) and the sub-critical accretion (pencil-beam dominated) mode. From the accretion torque model and the critical luminosity model, based on a distance of 7.1 kpc, the inferred magnetic fields are (0.41 − 0.74) × 1012 G and (3.48 − 3.96) × 1012 G, respectively, or based on a distance of 3.6 kpc, the estimated magnetic fields are (2.4 − 4.3) × 1013 G and (0.98 − 1.11) × 1012 G, respectively. Two different sets of magnetic fields both support the presence of multipole magnetic fields of the NS. © 2023, CC BY-NC-ND.

关键词： Luminance

Effect of Tidal Torques on Rotational Mixing in Close Binaries

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Chinese Physics Letters 2018年第7期35卷 139-143页

作者：李志宋汉峰彭卫国 College of Physics Guizhou University Geneva Observatory University of Geneva Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences

The effect of tidal torques on rotational mixing in close binaries is investigated. It is found that spin angular momentum can attain a high value due to a strong tidal torque. Nitrogen and helium enrichment occurs early in the binary system that is triggered by tides. The stellar radius can reach a high value in the single star model with high initial velocities at the early stage of the evolution, but efficient rotational mixing can inhibit stellar expanding at the subsequent evolution. Central compactness is increased by the centrifugal force at the early stage of evolution but is reduced by rotational mixing induced by strong tides. The binary models with weak tides have high values of central temperature and stellar radius. Rotational mixing in single stars can slow down the shrinkage of convective cores, while convective cores can be expanded by strong tides in the binary *** rotational mixing induced by tides can cause the star to evolve towards high temperature and luminosity.

关键词： Tides