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arXiv 2024年

作者： Peng, Zhao-Yang Chen, Jia-Ming Mao, Jirong College of Physics and Electronics Information Yunnan Normal University Kunming650500 China School of Physics and Astronomy Yunnan University Kunming650500 China Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing100101 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650011 China

GRB 211211A is a peculiar long Gamma-ray burst (GRB) with very high brightness and short burst properties. It’s full lightcurve consists of three emission episodes, i.e. a precursor, a main burst and a extended emission. We find a recently detected long-duration GRB 230307A also includes the three consistent emission episodes. Furthermore, the two bursts have similar redshift 0.076 and 0.065, respectively. We perform a detail temporal and spectral analysis of the two GRBs to compare their temporal and spectral properties. Our analysis shows that the two bursts share great similarities for both the whole emission and the three corresponding emission phases, which are listed as follows: (1) they have near zero spectral lag, (2) they have very short minimum variability timescale (MVT), (3) they lie in the same region of in the MVT-T90, Amati relation, and hardness-T90 planes, (4) the three phases are quasi-thermal spectra, (5) both the peak energy and the low-energy index track the flux, (6) the time-resolved spectra are much wider than those of the blackbody prediced by theory model, (7) there are strong correlations between thermal flux and total flux and the correlation coefficients as well as the slopes for the corresponding stages are very consistent, (8) the photosphere emission properties are very consistent. Other investigations and observations suggest the two GRBs indeed belong to short burst with a compact star merger origin. Therefore, we think that GRB 230307A and GRB 211211A are the rare and similar GRBs and the photospheric radiation can interpret their radiation mechanisms. Copyright © 2024, The Authors. All rights reserved.

关键词： Spectrum analysis

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On the External Inverse Compton Scattering off the Prompt Emission in GRB 221009A

arXiv

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arXiv 2024年

作者： Dai, Cui-Yuan Zheng, Jian-He Zhao, Xiao-Hong Liu, Ruo-Yu Wang, Xiang-Yu School of Astronomy and Space Science Nanjing University Nanjing210023 China Ministry of Education Nanjing210023 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

The light curve of the TeV emission in GRB 221009A displays a smooth transition from an initial rapid rise to a slower rise and eventually a decay phase. The smooth temporal profile of the TeV emission suggests that it mainly results from an external shock. The temporal overlap between the prompt KeV-MeV emission and the early TeV afterglow indicates that external inverse Compton scattering (EIC) between the prompt KeV-MeV photons and the afterglow electrons is inevitable. Since the energy density of the prompt emission is much higher than that of the afterglow during the early phase, the EIC process dominates the cooling of afterglow electrons. The EIC scattering rate is influenced by the anisotropy of the seed photon field, which depends on the radii of the internal dissipation (Rdis), where the prompt emission is produced, and that of the external shock (Rext), where the afterglow emission is produced. We investigate the EIC process for different values of Rdis/Rext. We find that, for varying Rdis/Rext, the EIC scattering rate can differ by a factor of ∼ 2. For GRB 221009A, the EIC emission is dominated during the early rising phase of the TeV afterglow. It then transitions to a phase dominated by the synchrotron self-Compton (SSC) emission as the intensity of the prompt emission decreases. Additionally, we investigate the effect of γγ absorption in the TeV afterglow caused by prompt MeV photons and find that it is insufficient to explain the early rapid rise in the TeV afterglow, even in the case of Rdis/Rext ∼ 1. Copyright © 2024, The Authors. All rights reserved.

关键词： Photons

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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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CSS_J154915.7+375506: A low-mass-ratio marginal contact binary system with a hierarchical third body

arXiv

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arXiv 2024年

作者： Wu, Jin-Feng Zhu, Li-Ying Matekov, Azizbek Li, Lin-Jia Ehgamberdiev, Shuhrat Asfandiyarov, Ildar Wang, Jiang-Jiao Zhang, Jia Meng, Fang-Bin Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Ulugh Beg Astronomical Institute of the Uzbekistan Academy of Science Astronomicheskaya 33 Tashkent100052 Uzbekistan National University of Uzbekistan 4 University str Tashkent100174 Uzbekistan

We presented the multi-filter light curves of CSS_J154915.7+375506 inaugurally, which were observed by the 1.5 m AZT-22 telescope at Maidanak Astronomical Observatory. A low-resolution spectrum obtained by LAMOST reveals it is an A-type close binary. By analyzing the BVRI total-eclipse light curves, we are able to derive a reliable photometric solution for this system, which indicates that CSS_J154915.7+375506 is an extremely low-mass-ratio (q=0.138) marginal contact binary system. The location in the HR diagram shows that its secondary component with a much smaller mass is the more evolved one, indicating the mass ratio reversal occurred. The present secondary component had transferred a significant amount of mass to the present primary one. By the combination of a total of 20 times of minimum, we investigated its O-C curve. A periodic oscillation and a possible period decrease have been detected. As the period decreases, the system will evolve towards the contact phase. This makes CSS_J154915.7+375506 a valuable case to study the formation scenario of contact binaries through mass reversal. The periodic oscillation suggested a third body with a minimal mass of 0.91 M☉, which is larger than that of the less massive component in the central binary. This implies that the secondary body was not replaced by the third body during early stellar interactions, indicating that it is a fossil system and retains its original dynamical information. © 2024, CC BY-NC-ND.

关键词： Systems (metallurgical)

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Radial velocity variability fractions of different types of hot subdwarf stars

arXiv

引用

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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Detection of 12426 SB2 candidates in the LAMOST-MRS, using a binary spectral model

arXiv

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arXiv 2023年

作者： Kovalev, Mikhail Zhou, Zenghua 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 Leninskie Gory Moscow119992 Russia Center for Astronomical Mega-Science Chinese Academy of Sciences 20A Datun Road Chaoyang District Beijing100012 China

We use an updated method for the detection of double-lined spectroscopic binaries (SB2) using V sin i values from spectral fits. The method is applied to all spectra from LAMOST MRS. Using this method, we detect 12426 SB2 candidates, where 4321 are already known and 8105 are new discoveries. We check their spectra manually to minimise possible false positives. We also detect several cases of contamination of the spectra by solar light. Additionally, for candidates with multiple observations we compute mass ratios with systemic velocities and determine Keplerian orbits. We present an updated catalogue of all SB2 candidates together with additional information for some of them in separate data tables. Copyright © 2023, The Authors. All rights reserved.

关键词： Orbits

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Predicting Astrometric Microlensing Events from Gaia DR3

arXiv

引用

arXiv 2023年

作者： Su, Jie Wang, Jiancheng Zhang, Yigong Cheng, Xiangming Yang, Lei Yunnan Observatories Chinese Academy of Sciences Kunming650216 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 Beijing100012 China University of Chinese Academy of Sciences Beijing100049 China College of Information Engineering Kunming University Kunming650214 China

Currently astrometric microlensing is the only tool that can directly measure the mass of a single star, it can also help us to detect compact objects like isolated neutron stars and black holes. The number of microlensing events that are being predicted and reported is increasing. In the paper, the potential lens stars are selected from three types of stars, high-proper-motion stars, nearby stars and high-mass stars. For each potential lens star, we select a larger search scope to find possible matching sources to avoid missing events as much as possible. Using Gaia DR3 data, we predict 4500 astrometric microlensing events with δθ+ > 0.1mas that occur between J2010.0 and J2070.0, where 1664 events are different from those found previously. There are 293 lens stars that can cause two or more events, where 5 lens stars can cause more than 50 events. We find that 116 events have the distance of background stars from the proper motion path of lens stars more than 8′′ in the reference epoch, where the maximum distance is 16.6′′, so the cone search method of expanding the search range of sources for each potential lens star can reduce the possibility of missing events. © 2023, CC BY.

关键词： Object detection

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A New Deep and Low-Mass-Ratio Contact Binary V2769 Orionis

SSRN

引用

SSRN 2023年

作者： Meng, Fangbin Zhu, LiYing Matekov, Azizbek Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming650216 China Ulugh Beg Astronomical Institute Uzbekistan Academy of Sciences 33 Astronomicheskaya str. Tashkent100052 Uzbekistan

We carried out the first multi-colour light curves analysis of the eclipsing binary V2769 Ori. The photometric solution was determined by applying the Wilson–Devinney method. The results show that V2769 Ori is a deep, low-mass-ratio contact binary with a mass ratio of q = 0.162(±0.003) and a contact degree of f = 55(±8)%. The total eclipse characteristics of V2769 Ori imply that the photometric solutions we obtained are reliable. With all available light minimum times, the O-C diagram was constructed and analyzed. The orbital period analysis reveals a long term period decrease at a rate of dp/dt = −1.24(±0.08) × 10−6 d yr−1 and a periodic oscillation with a period of 8.77 years. The secular period decrease can be explained by a combination of mass transfer from the more massive component to the less massive one and angular momentum loss via magnetic braking. As the orbital period decreases, the shrinking of the inner and outer critical Roche lobes causes an increase in contact degree, and the binary system will finally merge into a rapidly rotating star. Periodic oscillation may be the result of light-travel time effects due to the presence of unseen components. © 2023, The Authors. All rights reserved.

关键词： Travel time

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Two Different Weak Modulations in ab-type RR Lyrae Variable V838 Cyg, and Potential Influence of Metal Abundance on Blazhko Modulation

arXiv

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arXiv 2023年

作者： Li, L.-J. Qian, S.-B. Shi, X.-D. Zhu, L.-Y. Yunnan Observatories Chinese Academy of Sciences P.O. Box 110 Kunming650216 China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China University of Chinese Academy of Sciences No.1 Yanqihu East Rd Huairou District Beijing101408 China

Noting the weakest modulation and relatively high metal abundance of the ab-type RR Lyrae star V838 Cyg, we collected the photometric data of this star from several sky surveys to carry out an in-depth analysis. The O - C diagram shows that the pulsation period of V838 Cyg increases linearly over a long timescale. In a reanalysis of the high-precision Kepler data, we confirmed the modulation with a period of 59.45 ± 0.07 days found by Benko et al., (2014), and also found an additional weak modulation with a longer period (840±21 days). After a series of analyses, we incline to the view that the mechanisms causing the two modulations are different: the former is more similar to the typical Blazhko effect, while the mechanism leading to the latter may be an extrinsic factor. We also collected and compared the modulation and physical parameters of other Blazhko RR Lyrae stars from several works in the literature, and find that there is a potential negative correlation between the modulation amplitude (or upper limit of amplitude) and the metal abundance. We infer that the relatively high metal abundance will promote convection in the outer stellar atmosphere, and then inhibit those factors (turbulence, shock wave, etc.) that may cause Blazhko modulation. Future observations and research work can be carried out with reference to this viewpoint. We also introduce the moiré effects that appear in the Kepler long-cadence light curves and their possible interference in the previous analyses. © 2023, CC BY.

关键词： Shock waves

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Study of Advective Energy Transport in the Inflow and the Outflow of Super-Eddington Accretion Flows

arXiv

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arXiv 2023年

作者： Jiao, Cheng-Liang 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

Photon trapping is believed to be an important mechanism in super-Eddington accretion, which greatly reduces the radiative efficiency as photons are swallowed by the central black hole before they can escape from the accretion flow. This effect is interpreted as the radial advection of energy in one-dimensional height-integrated models, such as the slim disk model. However, when multi-dimensional effects are considered, the conventional understanding may no longer hold. In this paper, we study the advective energy transport in super-Eddington accretion, based on a new two-dimensional inflow-outflow solution with radial self-similarity, in which the advective factor is calculated self-consistently by incorporating the calculation of radiative flux, instead of being set as an input parameter. We found that radial advection is actually a heating mechanism in the inflow due to compression, and the energy balance in the inflow is maintained by cooling via radiation and vertical (θ-direction) advection, which transports entropy upwards to be radiated closer to the surface or carried away by the outflow. As a result, less photons are advected inwards and more photons are released from the surface, so that the mean advective factor is smaller and the emergent flux is larger than those predicted by the slim disk model. The radiative efficiency of super-Eddington accretion thus should be larger than that of the slim disk model, which agrees with the results of some recent numerical simulations. Copyright © 2023, The Authors. All rights reserved.

关键词： Advection

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