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The afterglow emission from a stratified jet in GRB 170817A

Research in Astronomy and Astrophysics 2021年第7期21卷 223-233页

作者： Kang-Fa Cheng Xiao-Hong Zhao Bin-Bin Zhang Jin-Ming Bai Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of the Chinese Academy of Sciences Beijing 100049China 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 School of Astronomy and Space Science Nanjing UniversityNanjing 210093China Key Laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210046China Department of Physics and Astronomy University of Nevada Las VegasNV 89154USA

The afterglow of GRB 170817 A has been detected for more than three years,but the origin of the multi-band afterglow light curves remains under debate.A classical top-hat jet model is faced with difficulties in producing a shallow rise of the afterglow light curves as observed(E_(v) ∝ T^(0.8)).Here we reconsider the model of stratified ejecta with an energy profile of E(> Γβ)=E_0(Γβ)^(-k) as the origin of the afterglow light curves of the burst,where Γ and β are the Lorentz factor and speed of the ejecta,respectively.k is the power-law slope of the energy *** consider that the ejecta are collimated into *** kinds of jet evolutions are investigated,including a lateral-spreading jet and a non-lateral-spreading *** fit the multi-band afterglow light curves,including the X-ray data at one thousand days post-burst,and find that both the models of the spreading and non-spreading jets can fit the light curves well,but the observed angular size of the source and the apparent velocity of the flux centroid for the spreading jet model are beyond the observation limits,while the non-spreading jet model meets the observation *** of the best-fit parameters for the non-spreading jet model,such as the number density of the circumburst medium~10^(-2) cm^(-3) and the total jet kinetic energy E ~ 4.8 × 10^(51) erg,also appear *** best-fit slope of the jet energy profile is k ~*** results suggest that the afterglow of GRB 170817 A may arise from the stratified jet and that the lateral spreading of the jet is not significant.

关键词： gamma-ray burst:general stars:jets relativistic processes

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On the rotation properties of a post-explosion helium-star companion in Type Iax supernovae

arXiv

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arXiv 2022年

作者： Zeng, Yaotian Liu, Zheng-Wei Meng, Xiangcun Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China University of Chinese Academy of Science Beijing100012 China Center for Astronomical Mega-Science CAS Beijing100012 China

Recent studies have suggested that type Iax supernovae (SNe Iax) are likely to result from a weak deflagration explosion of a Chandrasekhar-mass white dwarf in a binary system with a helium (He)-star companion. Assuming that most SNe Iax are produced from this scenario, in this work we extend our previous work on the three-dimensional hydrodynamical simulation of ejecta-companion interaction by taking the orbital and spin velocities of the progenitor system into account. We then follow the post-impact evolution of a surviving He-star companion by using the one-dimensional stellar evolution code MESA. We aim to investigate the post-explosion rotation properties of a He-star companion in SNe Iax. We find that the He-star companion spins down after the impact due to the angular-momentum loss and expansion caused by the mass-stripping and shock heating during the interaction. This leads to the situation where the surface rotational speed of the surviving companion can drop to one-third of its pre-explosion value when it expands to a maximum radius a few years after the impact. Subsequently, the star shrinks and spins up again once the deposited energy is released. This spin-switching feature of the surviving He-star companions of SNe Iax may be useful for the identification of such objects in future observations. Copyright © 2022, The Authors. All rights reserved.

关键词： Helium

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The Red Supergiant Progenitor of Type II Supernova 2024ggi

arXiv

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arXiv 2024年

作者： Xiang, Danfeng Mo, Jun Wang, Xiaofeng Wang, Lingzhi Zhang, Jujia Lin, Han Chen, Liyang Song, Cuiying Liu, Liang-Duan Wang, Zhenyu Li, Gaici Department of Physics Tsinghua University Beijing100084 China National Astronomical Observatories CAS Beijing100101 China Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Institute of Astrophysics Central China Normal University Wuhan430079 China Key Laboratory of Quark and Lepton Physics Central China Normal University Ministry of Education Wuhan430079 China University of Chinese Academy of Sciences Beijing100049 China

We present a detailed analysis of the progenitor and its local environment for the recently discovered type II supernova (SN) 2024ggi at a distance of about 6.7 Mpc, by utilizing the pre-explosion images from the Hubble Space Telescope (HST) and Spitzer Space Telescope. The progenitor is identified as a red, bright variable star, with absolute F814W-band magnitudes being -6.2 mag in 1995 to -7.2 mag in 2003, respectively, consistent with that of a normal red supergiant (RSG) star. Combining with the historical mid-infrared light curves, a pulsational period of about 379 days can be inferred for the progenitor star. Fitting its spectral energy distribution with stellar spectral models yields the stellar parameters of temperature, radius and bolometric luminosity as T*= 3290+19 -27 K, R*= 887+60 -51 Ro, and log(L/Lo)= 4.92+0.05 -0.04, respectively. The above parameters indicate that the progenitor of SN 2024ggi is consistent with the stellar evolutionary track of a solar-metallicity massive star with an initial mass of 13+1 -1 Mo. Moreover, our analysis indicates a relatively low mass loss rate (i.e., © 2024, CC BY.

关键词： Supernovae

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Black Hole Ultracompact X-Ray Binaries as Galactic Low-frequency Gravitational Wave Sources: the He Star Channel

arXiv

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arXiv 2023年

作者： Qin, Ke Xu, Kun Liu, Dong-Dong Jiang, Long Wang, Bo Chen, Wen-Cong School of Science Qingdao University of Technology Qingdao266525 China School of Physics Zhengzhou University Zhengzhou450001 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories Chinese Academy of Sciences Kunming650216 China School of Physics and Electrical Information Shangqiu Normal University Shangqiu476000 China

Black hole (BH) ultracompact X-ray binaries (UCXBs) are potential Galactic low-frequency gravitational wave (GW) sources. As an alternative channel, BH UCXBs can evolve from BH+He star binaries. In this work, we perform a detailed stellar evolution model for the formation and evolution of BH UCXBs evolving from the He star channel to diagnose their detectability as low-frequency GW sources. Our calculations found that some nascent BH+He star binaries after the common-envelope (CE) phase could evolve into UCXB-LISA sources with a maximum GW frequency of ∼ 5 mHz, which can be detected in a distance of 10 kpc (or 100 kpc). Once BH+He star systems become UCXBs through mass transfer, they would emit X-ray luminosities of ∼ 1038 erg s−1, making them ideal multimessenger objects. If the initial He-star masses are ≥ 0.7M☉, those systems are likely to experience two Roche lobe overflows, and the X-ray luminosity can reach a maximum of 3.5 × 1039 erg s−1 in the second mass-transfer stage. The initial He-star masses and initial orbital periods of progenitors of Galactic BH UCXB-LISA sources are in the range of 0.32-2.9 M☉ and 0.02-0.19 days, respectively. Nearly all BH+He star binaries in the above parameter space can evolve into GW sources whose chirp masses can be accurately measured. Employing a population synthesis simulation, we predict the birthrate and detection number of Galactic BH UCXB-LISA source evolving from the He star channel are R = 2.2 × 10−6 yr−1 and 33 for an optimistic CE parameter, respectively. © 2023, CC0.

关键词： Gravity waves

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A Scenario for Origin of Global 4 mHz Oscillations in Solar Corona

arXiv

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arXiv 2025年

作者： Xue, Li Jiao, Chengliang Zhang, Lixin Department of Astronomy Xiamen Univesity Xiamen361005 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

We establish a spherically symmetric model of solar atmosphere, which consists of the whole chromosphere and low corona below the 1.25 solar radius. It is a hydrodynamic model with heating in the chromosphere through an artificial energy flux. We performed a series of simulations with our model and found oscillations with a peak frequency of ∼4 mHz in the power spectrum. We confirmed that this resulted from the p-mode excited in the transition region and amplified in a resonant cavity situated in the height range ∼4 × 103-2 × 104 km. This result is consistent with global observations of Alfvénic waves in corona and can naturally explain the observational ubiquity of 4 mHz without the difficulty of the p-mode passing through the acoustic-damping chromosphere. We also confirmed that acoustic shock waves alone cannot heat the corona to the observed temperature, and found mass upflows in the height range ∼7 × 103-7 × 104 km in our model, which pumped the dense and cool plasma into the corona and might be the mass supplier for solar prominences. © 2025, CC BY.

关键词： Plasma shock waves

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Synchrotron Circular Polarization in Gamma-Ray Burst Prompt Optical Emission: Relativistic Thermal Electron Contribution

arXiv

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arXiv 2025年

作者： Cheng, Kangfa Mao, Jirong Zhao, Xiaohong Liu, Hongbang Chen, Zhegeng Yu, Gaojin Chen, Zhifu Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and Technology Guangxi University Nanning530004 China School of Physics and Electronic Information Guangxi Minzu University Nanning530006 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China

Synchrotron circular polarization of a non-thermal power-law electron distribution in gamma-ray bursts (GRBs) has been studied. However, some numerical simulations have shown that the resulting distribution of electrons is a combination of a thermal component and a non-thermal power-law component. In this paper, we investigate synchrotron circular polarization using such a hybrid energy distribution of relativistic thermal and nonthermal electrons within a globally toroidal magnetic field in GRB prompt optical emission. Our results show that compared to the solely nonthermal electron model, the synchrotron circular polarization degree (PD) in the hybrid electron model can vary widely in the optical band, depending on different parameters. The lower the electron temperature, the higher the circular PD. The time-averaged circular PD in the hybrid electron model can be higher than ∼ 1% when the electron temperature is as low as ∼ 1010 K, while in the solely nonthermal electron model is usually lower than ∼ 1%. We further calculate the radiative transfer of the circular and linear polarization in the optical band. Our results show that both of the circular and linear PDs decrease with the increase of optical depth, but the linear PDs decline faster than the circular PDs. To further examine the physical mechanisms of both radiation and particle acceleration, we expect that instruments will be capable of measuring the circular polarization of GRB prompt optical emission in the future. Copyright © 2025, The Authors. All rights reserved.

关键词： Circular polarization

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Radial velocity variability fractions of different types of hot subdwarf stars

arXiv

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arXiv 2024年

作者： He, Ruijie Meng, Xiangcun Lei, Zhenxin Yan, Huahui Lan, Shunyi Yunnan Observatories Chinese Academy of Sciences Kunming650011 China University of the Chinese Academy of Sciences Beijing100049 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 Key Laboratory of Stars and Interstellar Medium Xiangtan University Xiangtan411105 China Physics Department Xiangtan University Xiangtan411105 China Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and Physics Shandong University at Weihai Weihai264209 China

Context. It is generally thought that hot subdwarfs are helium-core- or helium-shell-burning objects with extremely thin hydrogen envelopes and that binary interactions are always needed in their formation. Different types of hot subdwarfs may have different origins, which will cause them to present different radial velocity (RV) variability properties. Aims. We plan to study the RV-variability fractions of different types of hot subdwarfs, as well as their distributions in the Teff – log g diagram. This provides insights into the formation of hot subdwarfs. Methods. The cross-correlation function method was adopted to measure RV variations in 434 hot subdwarfs based on spectra obtained with the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST). Light curves from the Transiting Exoplanet Survey were also used to search for short-period binary hot subdwarfs. Results. Only 6 ± 4% of our single-lined He-rich hot subdwarfs that only show spectroscopic features of hot subdwarfs are found to be RV variable, which is lower than the fraction of single-lined He-poor sdB stars (31 ± 3%). Single-lined sdB stars with effective temperatures (Teff) ∼ 25,000 – 33,000 K show an RV-variability fraction of 34 ± 5%, while lower RV-variability fractions are observed for single-lined sdB stars cooler than about 25,000 K (11 ± 4%), single-lined sdB/OB stars with Teff ∼ 33,000 – 40,000 K and surface gravities ∼ 5.7 – 6.0 (13 ± 3%), as well as single-lined sdO/B stars with Teff ∼ 45,000 – 70,000 K (10 ± 7%). Single-lined hot subdwarfs with Teff ∼ 35,000 – 45,000 K located above the extreme horizontal branch (EHB) show a similar RV-variability fraction of 34 ± 9% as single-lined sdB stars at about 25,000 – 33,000 K. The largest RV-variability fraction of 51 ± 8% is found in single-lined hot subdwarfs below the canonical EHB. The detected RV-variability fraction of our composite hot subdwarfs with an infrared excess in their spectral energy distributions is 9 ± 3%, which is

关键词： Exoplanets

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Surface brightness-color relations for red giant branch stars using asteroseismic radii and Gaia distances (the ARD method)

arXiv

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arXiv 2025年

作者： Xiong, Jianping Cheng, Qiyuan Chen, Xiaodian Li, Jiao Zhang, Xiaobin Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 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 CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Science University of the Chinese Academy of Sciences Beijing101408 China Department of Astronomy China West Normal University Nanchong China

Context. Surface brightness-color relations (SBCRs) are essential for estimating distances and stellar properties. Previously, SBCRs were based on a limited number of red clump giant (RC) stars, and red giant branch (RGB) stars with infrared interferometric measurements or eclipsing binaries with high-precision radii measurements, resulting in discrepancies in precision and accuracy. Recently, the large number of RGB stars with asteroseismic parameters and precise Gaia distance measurements has enabled the development of more accurate and robust SBCRs. Aims. Asteroseismic radius and Gaia distance (ARD) method has been proposed to establish the SBCRs for late-type stars. Methods. We select Kepler RGB stars with high-precision asteroseismic radii (uncertainties s-band photometric data. After applying selection criteria, we obtain 626 RGB stars to build the SBCR. Among these, 100 RGBs are used as independent validation for the distance, and the remaining samples are used to fit the SBCR. Results. First, using 526 targets with asteroseismic radii and Gaia distances, nine SBCRs are proposed based on 2MASS (J, H, Ks), APASS (Johnson-B, Johnson-V), and Gaia (G) photometry. The average rms scatter in these relations is 0.075 mag, which corresponds to an uncertainty of approximately 3.5% in distance. These relations are further validated using 100 independent samples with Gaia distances, showing no bias, with a dispersion of approximately 3%. Compared to interferometric measurements, a systematic underestimation of 2.3% was observed, and the discrepancy decreases as the angular diameter increases. Additionally, the distances of eclipsing binaries in the Large Magellanic Cloud and Small Magellanic Cloud obtained using our SBCRs are generally consistent with those measured in the literature, with a dispersion of 1% and a slight overestimation of 1% to 2.5%. Conclusions. The ARD method capitalizes on two key advantages for precise stellar distance determination: a statistically

关键词： Luminance

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Does Nature allow formation of ultra-compact black hole X-ray binaries via accretion-induced collapse of neutron stars?

arXiv

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arXiv 2023年

作者： Chen, Hai-Liang Tauris, Thomas M. Chen, Xuefei Han, Zhanwen Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Department of Materials and Production Aalborg University Skjernvej 4A Aalborg ØstDK-9220 Denmark University of the Chinese Academy of Sciences Yuquan Road 19 Shijingshan Block Beijing100049 China

The formation path to ultra-compact X-ray binaries (UCXBs) with black hole (BH) accretors is still unclear. In the classical formation scenario, it is difficult to eject the massive envelope of the progenitor star of the BH via common envelope process. Given that some neutron stars (NSs) in binary systems evidently have birth masses close to ∼ 2.0 M☉, we explore here the possibility that BH-UCXBs may form via accretion-induced collapse (AIC) of accreting NSs, assuming that these previously evolved in LMXBs to masses all the way up to the maximum limit of a NS. We demonstrate this formation path by modelling a few cases of NS-UCXBs with initial NS masses close to the maximum mass of a NS that evolve into BH-UCXBs after the NS accretes material from its He WD companion. We follow the evolution of the post-AIC BH-UCXB and, based on simple arguments, we anticipate that there is about one BH-UCXB with an AIC origin and a He WD donor within the current sample of known UCXBs and that 2-5 such BH-UCXBs may be detected in gravitational waves by LISA. In addition, we find that the X-ray luminosity of NS-UCXBs near their orbital period minimum exceeds ∼ 1039 erg s−1 and thus such systems may appear as ultraluminous X-ray sources. © 2023, CC BY.

关键词： Gravity waves

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Prominence detection and chromosphere feature on the prototype RS CVn of active binary systems

arXiv

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arXiv 2024年

作者： Cao, Dongtao Gu, Shenghong Wolter, U. Mittag, M. Schmitt, J.H.M.M. Gao, Dongyang Hu, Shaoming 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 Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China Hamburger Sternwarte Universität Hamburg HamburgD-21029 Germany Shandong Provincial key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space Sciences Shandong University Weihai264209 China

We present a study of high-resolution spectra of RS Canum Venaticorum (RS CVn), a prototype of active binary systems. Our data were obtained from 1998 to 2017 using different telescopes. We analyze the chromospheric activity indicators Ca ii IRT, Hα, Na i D1, D2 doublet, He i D3, and Hβ using a spectral subtraction technique. The chromospheric emission stems mainly from the K2 IV primary star, while the F5 V secondary star only shows weak emission features in a few of our spectra. We find excess absorption features in the subtracted Hα lines and other activity indicators from spectra taken near primary eclipse, which we ascribe to prominence-like material associated with the primary star. We estimate size limits of these tentative prominences based on the geometry of the binary system, and investigate the physical properties of the strongest prominence. An optical flare, characterized by He i D3 line emission, together with stronger emission in other activity lines, was detected. The flare energy is roughly comparable to strong flares observed on other RS CVn-type stars. The chromospherically active longitudes of RS CVn most frequently appear near the two quadratures of the system and display changes between observing runs, which indicates an ongoing evolution of its active regions. Copyright © 2024, The Authors. All rights reserved.

关键词： Chromophores

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