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arXiv 2024年

作者： Zhang, Yan-Qiu Xiong, Shao-Lin Mao, Ji-Rong Zhang, Shuang-Nan Xue, Wang-Chen Zheng, Chao Liu, Jia-Cong Zhang, Zhen Wang, Xi-Lu Ge, Ming-Yu Yi, Shu-Xu Song, Li-Ming An, Zheng-Hua Cai, Ce Li, Xin-Qiao Peng, Wen-Xi Tan, Wen-Jun Wang, Chen-Wei Wen, Xiang-Yang Wang, Yue Xiao, Shuo Zhang, Fan Zhang, Peng Zheng, Shi-Jie Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China University of Chinese Academy of Sciences Beijing100049 China Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China College of Physics Hebei Key Laboratory of Photophysics Research and Application Hebei Normal University Hebei Shijiazhuang050024 China Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing Guizhou Normal University Guiyang550001 China College of Electronic and Information Engineering Tongji University Shanghai201804 China

As the brightest gamma-ray burst ever observed, GRB 221009A provided a precious opportunity to explore spectral line features. In this paper, we performed a comprehensive spectroscopy analysis of GRB 221009A jointly with GECAM-C and Fermi/GBM data to search for emission and absorption lines. For the first time we investigated the line feature throughout this GRB including the most bright part where many instruments suffered problems, and identified prominent emission lines in multiple time intervals. The central energy of the Gaussian emission line evolves from about 37 MeV to 6 MeV, with a nearly constant ratio (about 10%) between the line width and central energy. Particularly, we find that both the central energy and the energy flux of the emission line evolve with time as a power law decay with power law index of -1 and -2 respectively. We suggest that the observed emission lines most likely origin from the blue-shifted electron positron pair annihilation 511 keV line. We find that a standard high latitude emission scenario cannot fully interpret the observation, thus we propose that the emission line comes from some dense clumps with electron positron pairs traveling together with the jet. In this scenario, we can use the emission line to directly, for the first time, measure the bulk Lorentz factor of the jet (Γ) and reveal its time evolution (i.e. Γ ∼ t−1) during the prompt emission. Interestingly, we find that the flux of the annihilation line in the co-moving frame keeps constant. These discoveries of the spectral line features shed new and important lights on the physics of GRB and relativistic jet. Copyright © 2024, The Authors. All rights reserved.

关键词： Gamma rays

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WASP-35 and HAT-P-30/WASP-51: re-analysis using TESS and ground-based transit photometry

arXiv

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arXiv 2022年

作者： Bai, Lu Gu, Shenghong Wang, Xiaobin Sun, Leilei Kwok, Chi-Tai Hui, Ho-Keung Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Ho Koon Nature Education cum Astronomical Centre Sik Sik Yuen China

High-precision transit observations provide excellent opportunities for characterizing the physical properties of exoplanetary systems. These physical properties supply many pieces of information for unvealing the internal structure, external atmosphere, and dynamical history of the planets. We present revised properties of transiting systems WASP-35 and HAT-P-30/WASP-51 through analyzing newly available TESS photometry and ground-based observations obtained at 1m telescope of Yunnan Observatories as well as from the literature. The improved system parameters are consistent with the previous results. Furthermore, we find that HAT-P-30b/WASP-51b’s transits show significant timing variation which cannot be explained by decaying orbit due to tidal dissipation and the Rømer effect, while both apsidal precession and an additional perturbing body could reproduce this signal through our comprehensive dynamical simulations. Because both of them are valuable targets which are suitable for transmission spectroscopy, we make some predictions for atmospheric properties of WASP-35b and HAT-P-30b/WASP-51b based on newly derived system parameters. Copyright © 2022, The Authors. All rights reserved.

关键词： Monte Carlo methods

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New simulations of the X-ray spectra and polarizations of accretion-disc corona systems with various geometrical configurations I. Model Description

arXiv

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arXiv 2022年

作者： Yang, Xiao-Lin Wang, Jian-Cheng Yang, Chu-Yuan 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 Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

Energetic X-ray radiations emitted from various accretion systems are widely considered to be produced by Comptonization in the hot corona. The corona and its interaction with the disc play an essential role in the evolution of the system and are potentially responsible for many observed features. However many intrinsic properties of the corona are still poorly understood, especially for the geometrical configurations. The traditional spectral fitting method is not powerful enough to distinguish various configurations. In this paper we intent to investigate the possible configurations by modeling the polarization properties of X-ray radiations. The geometries of the corona include the slab, sphere and cylinder. The simulations are implemented through the publicly available code, LEMON, which can deal with the polarized radiative transfer and different electron distributions readily. The results demonstrate clearly that the observed polarizations are dependent on the geometry of the corona heavily. The slab-like corona produces the highest polarization degrees, the following are the cylinder and sphere. One of the interesting things is that the polarization degrees first increase gradually and then decrease with the increase of photon energy. For slab geometry there exists a zero point where the polarization vanishes and the polarization angle rotates for 90◦. These results may potentially be verified by the upcoming missions for polarized X-ray observations, such as IXP E and eXT P . © 2022, CC BY.

关键词： Polarization

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Analysis of the possible satellite contamination in LAMOST-MRS spectra

arXiv

引用

arXiv 2023年

作者： Kovalev, Mikhail Hainaut, Olivier R. 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 of the M. V. Lomonosov Moscow State University Leninskie Gory Moscow119992 Russia European Southern Observatory Karl-Schwarzschild-Straße 2 Garching bei München85748 Germany Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We present the detection of false positive double-lined spectroscopic binaries candidates (SB2) using medium-resolution survey (MRS) spectra from the one time-domain field of LAMOST data release 10 (DR10). The secondary component in all these binaries has near zero radial velocity and solar-like spectral lines. Highly likely this is light from the semi-transparent clouds illuminated by the full Moon. However we also suspect that partially this contamination can be caused by a solar light reflected from the surface of low-orbital artificial satellites launched in the beginning of 2022. We found several possible contaminant candidates using archival orbital data. We propose measures to reduce risk of such contamination for the future observations and methods to find it in archived ones. Copyright © 2023, The Authors. All rights reserved.

关键词： Contamination

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Detection of Ubiquitous Circumbinary Matter in Hot Subdwarfs Formed from Common-Envelope Ejections

arXiv

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arXiv 2025年

作者： Li, Jiangdan Wolf, Christian Li, Jiao Luo, Yangping Zhao, Jingkun Chen, Bingqiu Zhang, Lin Jia, Shi Chen, Xuefei Han, Zhanwen 396 Yangfangwang Guandu District Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Research School of Astronomy and Astrophysics Australian National University Weston CreekACT2611 Australia Centre for Gravitational Astrophysics Australian National University CanberraACT2600 Australia Department of Astronomy China West Normal University Nanchong637002 China CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China South-Western Institute for Astronomy Research Yunnan University Kunming650504 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

The formation of compact binary systems is largely driven by their evolution through a common envelope (CE) phase, crucial for understanding phenomena such as type Ia supernovae and black hole mergers. Despite their importance, direct observational evidence for CE material has been elusive due to the transient nature of these envelopes. Numerical simulations suggest that some envelope material may persist post-ejection. In this study, we investigate circumstellar material (CSM) surrounding hot subdwarf (sdB) stars, focusing on material ejected during the CE phase of binary evolution. We analyze Ca II K absorption lines in 727 sdB candidates from the LAMOST-LRS survey, selecting 145 stars with strong absorption features, indicating the presence of CSM. We compare the velocities of the Ca II K lines with the systemic velocities of sdB binaries, confirming that the material originates from ejected common-envelope material. The results show that the CSM persists long after the CE event, suggesting the formation of a stable, long-lived circumstellar environment around sdB stars. This study enhances our understanding of the role of CSM in post-CE evolution and provides new insights into the physical processes shaping the evolution of sdB binaries. Copyright © 2025, The Authors. All rights reserved.

关键词： Supernovae

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Observational constraints on Rastall gravity from rotation curves of low surface brightness galaxies

引用

Chinese Physics C 2020年第8期44卷 217-224页

作者： Meirong Tang Zhaoyi Xu Jiancheng Wang Yunnan Observatories Chinese Academy of Sciences396 YangfangwangGuandu DistrictKunming 650216China Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences396 YangfangwangGuandu DistrictKunming 650216China Center for Astronomical Mega-Science Chinese Academy of Sciences20A Datun RoadChaoyang DistrictBeijing 100012China University of Chinese Academy of Sciences Beijing 100049China

Rastall gravity is a modification of Einstein's general relativity in which the energy-momentum conservation is not satisfied and depends on the gradient of the Ricci *** is currently in dispute whether Rastall gravity is equivalent to general relativity(GR).In this work,we constrain the theory using the rotation curves of low surface brightness(LSB)spiral *** fitting the rotation curves of LSB galaxies,we obtain parameterβof the Rastall ***βvalues of LSB galaxies satisfy the weak energy condition(WEC)and strong energy condition(SEC).Combining theβvalues of type Ia supernovae and the gravitational lensing of elliptical galaxies on Rastall gravity,we conclude that Rastall gravity may be equivalent to general relativity.

关键词： Rastall gravity energy condition LSB galaxies

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WD+AGB star systems as the progenitors of type Ia supernovae

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Proceedings of the International Astronomical Union 2019年第S343期14卷 540-541页

作者： Wang B. Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China

WD+AGB star systems have been suggested as an alternative way for producing type Ia supernovae (SNe Ia), known as the core-degenerate (CD) scenario. In the CD scenario, SNe Ia are produced at the final phase during the evolution of common-envelope through a merger between a carbon-oxygen (CO) WD and the CO core of an AGB secondary. However, the rates of SNe Ia from this scenario are still uncertain. In this work, I carried out a detailed investigation on the CD scenario based on a binary population synthesis approach. I found that the Galactic rates of SNe Ia from this scenario are not more than 20% of total SNe Ia due to more careful treatment of mass transfer, and that their delay times are in the range of â'1/490-2500 Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times. © International Astronomical Union 2019.

关键词： Binaries: Close Supernovae: General White dwarfs

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

引用

Astronomy and Astrophysics 2022年 667卷

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 M'0.06 M). 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 © Y. Cui et al. 2022.

关键词： Supernovae

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Can small-scale magnetic fields be the major cause for the near-surface effect of the solar p-mode frequencies?

arXiv

引用

arXiv 2021年

作者： Li, Yan Zhang, Qian-Sheng Wu, Tao Su, Jie Chen, Xing-Hao Lin, Gui-Fang Guo, Jian-Heng Liu, Jie-Ying Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China

Small-scale magnetic fields are not only the fundamental element of the solar magnetism, but also closely related to the structure of the solar atmosphere. The observations have shown that there is a ubiquitous tangled small-scale magnetic field with a strength of 60 ∼ 130 G in the canopy forming layer of the quiet solar photosphere. On the other hand, the multi-dimensional MHD simulations show that the convective overshooting expels the magnetic field to form the magnetic canopies at a height of about 500 km in the upper photosphere. However, the distribution of such small-scale "canopies" in the solar photosphere cannot be rigorously constrained by either observations and numerical simulations. Based on stellar standard models, we identify that these magnetic canopies can act as a global magnetic-arch splicing layer, and find that the reflections of the solar p-mode oscillations at this magnetic-arch splicing layer results in significant improvement on the discrepancy between the observed and calculated p-mode frequencies. The location of the magnetic-arch splicing layer is determined at a height of about 630 km, and the inferred strength of the magnetic field is about 90 G. These features of the magnetic-arch splicing layer derived independently in the present study are quantitatively in agreement with the presence of small-scale magnetic canopies as those obtained by the observations and 3-D MHD simulations. © 2021, CC BY.

关键词： Arches

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Magnetic-Reconnection-Heated Corona Model: Implication of Hybrid Electrons for Hard X-ray Emission of Luminous Active Galactic Nuclei

arXiv

引用

arXiv 2023年

作者： Liu, Jie-Ying Mao, Jirong Liu, B.F. Yunnan Observatories Chinese Academy of Sciences Yunnan Province Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences 19A Yuquan Road Beijing100049 China Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China Key Laboratory of Space Astronomy and Technology National Astronomical Observatories Chinese Academy of Sciences Beijing100012 China

It is widely accepted that X-ray emission in luminous active galactic nuclei (AGNs) originates from hot corona. To prevent the corona from over-cooling by strong X-ray emission, steady heating to the corona is essential, for which the most promising mechanisms is the magnetic reconnection. Detailed studies of the coupled disc and corona, in the frame of magnetic field transferring accretion-released energy from the disc to the corona, reveal that the thermal electrons can only produce X-ray spectrum with Γ2−10 keV > 2.1, which is an inevitable consequence of the radiative coupling of the thermal corona and disc. In the present work, we develop the magnetic-reconnection-heated corona model by taking into account the potential non-thermal electrons accelerated in the magnetic reconnection process, in addition to the thermal electrons. We show that the features of the structure and spectrum of the coupled disc and corona can be affected by the fraction of magnetic energy allocated to thermal electrons. Furthermore, we investigate the effects of the power-law index and energy range of non-thermal electrons and the magnetic field on the spectrum. It is found that the X-ray spectrum from the Comptonization of the hybrid electrons can be flatter than that from thermal electrons only, in agreement with observations. By comparing with the observed hard X-ray data, we suggest that a large fraction (> 40%) of the magnetic energy be allocated to the non-thermal electrons in the luminous and flat X-ray spectrum AGNs. Copyright © 2023, The Authors. All rights reserved.

关键词： Gamma rays

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