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arXiv 2023年

作者： Wang, Wenjie Yuan, Zunli Yu, Hongwei Mao, Jirong Department of Physics School of Physics and Electronics Hunan Normal University Changsha410081 China Key Laboratory of Low Dimensional Quantum Structures and Quantum Control Hunan Normal University Changsha410081 China Synergetic Innovation Center for Quantum Effects and Applications Institute of Interdisciplinary Studies Hunan Normal University Hunan Changsha410081 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 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

Context. Radio wavelengths offer a unique possibility to trace the total star-formation rate (SFR) in galaxies, both obscured and unobscured. To probe the dust-unbiased star-formation history, an accurate measurement of the radio luminosity function (LF) for star-forming galaxies (SFGs) is crucial. Aims. We make use of an SFG sample (5900 sources) from the Very Large Array (VLA) COSMOS 3 GHz data to perform a new modeling of the radio LF. By integrating the analytical LF, we aim to calculate the history of the cosmic SFR density (SFRD) from z ∼ 5 onwards. Methods. For the first time, we use both models of the pure luminosity evolution (PLE) and joint luminosity+density evolution (LADE) to fit the LFs directly to the radio data using a full maximum-likelihood analysis, considering the sample completeness correction. We also incorporate updated observations of local radio LFs and radio source counts into the fitting process to obtain additional constraints. Results. We find that the PLE model cannot be used to describe the evolution of the radio LF at high redshift (z > 2). By construct, our LADE models can successfully fit a large amount of data on radio LFs and source counts of SFGs from recent observations. The Akaike information criterion (AIC) also demonstrates that the LADE model is superior to the PLE model. We therefore conclude that density evolution is genuinely indispensable in modeling the evolution of SFG radio LFs. Our SFRD curve shows a good fit to the SFRD points derived by previous radio estimates. In view of the fact that our radio LFs are not biased, as opposed those of previous studies performed by fitting the 1/Vmax LF points, our SFRD results should be an improvement on these previous estimates. Below z ∼ 1.5, our SFRD matches a published multiwavelength compilation, while our SFRD turns over at a slightly higher redshift (2 © 2023, CC BY.

关键词： Luminance

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The preliminary statistical analysis of LAMOST DR8 low resolution AFGK stars

arXiv

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arXiv 2022年

作者： Chen, Yan hui Li, Guang Wei Shu, Hong Institute of Astrophysics Chuxiong Normal University Chuxiong675000 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Physics and Electronical Science Chuxiong Normal University Chuxiong675000 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650011 China

We download the LAMOST DR8 low resolution catalog 6,478,063 AFGK tpye stars and plot the figures of effective temperature, gravitational acceleration, and metal abundance. Some small and medium mass stars are evolved from pre-main sequence or main sequence stage to planetary nebula stage or white dwarf stage by the stellar evolution code MESA. We analyze the observed statistical data and model calculation results, and then obtain some basic conclusions preliminarily. Most red giant and asymptotic giant stars with logg less than 0.85 have poor metal abundance. Most hot A type main-sequence stars are metal rich stars with logg from 3.5 to 4.5. The conclusions are reasonable within a certain error range. The theory of a gap area in the H-R diagram for stellar evolutions of medium mass stars is reflected in the statistical figures. The central core hydrogen burning stage and the central core helium burning stage correspond to the peak structures in the gravitational acceleration statistical figures respectively. The metal abundances among A, F, G, and K type stars have a wide distribution. We can not simply replace the metal abundances of these stars with the metal abundance of the Sun when doing a fine research work. Copyright © 2022, The Authors. All rights reserved.

关键词： Metals

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SN 2021dbg: A Luminous Type IIP-IIL Supernova Exploding from a Massive Star with a Layered Shell

arXiv

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arXiv 2024年

作者： Zhao, Zeyi Zhang, Jujia Li, Liping Zhai, Qian Cai, Yongzhi Srivastav, Shubham Wang, Xiaofeng Lin, Han Yang, Yi Filippenko, Alexei V. Brink, Thomas G. Zheng, WeiKang Kunming650216 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming650216 China Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast BelfastBT7 1NN United Kingdom Department of Physics Tsinghua University Beijing100084 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing210023 China Key Laboratory of Radio Astronomy and Technology CAS A20 Datun Road Chaoyang District Beijing100101 China Department of Astronomy University of California BerkeleyCA94720-3411 United States

We present extensive observations and analysis of supernova (SN) 2021dbg, utilizing optical photometry and spectroscopy. For approximately 385 days following the explosion, SN 2021dbg exhibited remarkable luminosity, surpassing most SNe II. This initial high luminosity is potentially attributed to the interaction between the ejected material and the surrounding circumstellar material (CSM), as evidenced by the pronounced interaction signatures observed in its spectra. The subsequent high luminosity is primarily due to the significant 56Ni (0.17 ± 0.05 M☉) produced in the explosion. Based on the flux of flash emission lines detected in the initial spectra, we estimate that the CSM mass near the progenitor amounted to ∼(1.0–2.0) ×10−3 M☉, likely resulting from intense stellar wind activity 2–3 yr preceding the explosion. Considering the bolometric light curve, nebular spectrum modeling, and mass-loss rate, we suggest that the progenitor of SN 2021dbg was a red supergiant (RSG) with a mass of ∼ 20 M☉ and a radius of 1200 R☉. This RSG featured a thick hydrogen shell, which may have contained a region with a sharp decrease in material density, electron density, and temperature, contributing to its layered structure. This object demonstrates mixed features of SNe IIP and SNe IIL, making it as a transitional event linking the above two subclasses of SNe II. Copyright © 2024, The Authors. All rights reserved.

关键词： Supernovae

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Magnetic activities on two single-lined RS Canum Venaticorum binaries IM Pegasi and σ Geminorum

arXiv

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arXiv 2024年

作者： Cao, Dongtao Gu, Shenghong Grundahl, F. Pallé, P.L. 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 Stellar Astrophysics Centre Department of Physics and Astronomy Aarhus University NyMunkegade 120 Aarhus C8000 Denmark Instituto de Astrofísica de Canarias Tenerife La Laguna38205 Spain Universidad de La Laguna Departamento de Astrofísica Tenerife La Laguna38206 Spain

We present the study on continuous high-resolution spectroscopic observations of two long-period single-lined RS Canum Venaticorum (RS CVn) binary stars IM Pegasi (IM Peg) and σ Geminorum (σ Gem), obtained with the Hertzsprung SONG telescope during the 2015–2016 season. Chromospheric activity indicators Hα, Na i D1, D2 doublet, He i D3, and Hβ lines have been analyzed by using the spectral subtraction technique. The expected chromospheric emission features in the Hα, Na i D1, D2 doublet, and Hβ lines confirm that both of two stars are very active systems. In the spectra, the He i D3 line had been always detected in absorption feature. Although the behavior of chromospheric activity indicators is very similar for both stars, the activity level of IM Peg is much stronger than that of σ Gem. Moreover, the EW variations of the Hα, He i D3, and Hβ line subtractions correlate well and show different behavior among different orbital cycles, which indicates the presence and evolution of activity longitudes over the surface of two stars. Furthermore, the subtracted Hα line profile is usually asymmetric. The red-shifted excess absorption features could be interpreted as a strong down-flow of cool absorbing material, while the blue-shifted emission component is probably caused by up-flow of hot materials through microflare events. Copyright © 2024, The Authors. All rights reserved.

关键词： Stars

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The radius variations of accreting main-sequence stars and mass transfer instability

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Monthly Notices of the Royal Astronomical Society: Letters 2024年第1期531卷 L45-L51页

作者： Zhao, Zi-Qi Li, Zhen-Wei Xiao, Lin Ge, Hong-Wei Han, Zhan-Wen Department of Physics Hebei University Baoding 071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics College of Physics Science and Technology Hebei University Baoding 071002 China Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science Kunming 650011 China International Centre of Supernovae Yunnan Key Laboratory Kunming 650216 China University of the Chinese Academy of Science Yuquan Road 19 Shijingshan Block Beijing 100049 China

Many previous works studied the dynamical time-scale mass transfer stability criteria based on the donor response with neglecting the stellar structure of the accretor. In this letter, we investigate the radial response of accretors with mass accumulation and its effect on the binary mass transfer stability. We perform a series of detailed stellar evolution simulations with different types of accretors and obtain the radial variations of stars accreting at different rates. Since the time within which the donor loses half of the original mass has a correlation with the donor mass, we approximately obtain the mean mass transfer rate as a function of mass ratio. Assuming that the common envelope (CE) phase occurs if the accretor radius exceeds the outer Roche lobe radius, we obtain the critical mass ratio of dynamically unstable mass transfer. We find the critical mass ratios for donors filling their Roche lobes at the Main Sequence (MS) and Hertzsprung Gap (HG) stages are smaller than that derived from the radial response of the donor in the traditional way. Our results may suggest that the binary is easier to enter into the CE phase for a donor star at the MS or HG stage than previously believed. © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.

关键词： accretion, accretion discs binaries: close convection

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Influence of a mass transfer stability criterion on double white dwarf populations

arXiv

引用

arXiv 2022年

作者： Zhenwei, Li Xuefei, Chen Hongwei, Ge Hai-Liang, Chen Zhanwen, Han Yunnan Observatories Chinese Academy of Sciences Kunming650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Science China Center for Astronomical Mega-Science Chinese Academy of Science 20A Datun Road Chaoyang District Beijing100012 China University of the Chinese Academy of Sciences 19A Yuquan Road Shijingshan District Beijing100049 China

Context. Mass transfer stability is a key issue in studies of binary evolution. Critical mass ratios for dynamically stable mass transfer have been analyzed on the basis of an adiabatic mass loss model, finding that the donor stars on the giant branches tend to be more stable than that based on the composite polytropic stellar model. Double white dwarfs (DWDs) are of great importance in many fields and their properties would be significantly affected under the new mass transfer stability criterion. Aims. We seek to investigate the influence of mass transfer stability on the formation and properties of DWD populations and discuss the implications in supernova Type Ia (SN Ia) and gravitational wave (GW) sources. Methods. We performed a series of binary population synthesis, adopting the critical mass ratios from the adiabatic mass loss model (i.e., Ge’s model) and that of the composite polytropic model, respectively. In each simulation, 5 × 106 binaries were included and evolved from zero-age main sequence to the end of their evolution and the DWDs were gradually obtained. Results. For Ge’s model, most of the DWDs are produced from the stable non-conservative Roche lobe (RL) overflow, along with a common-envelope (CE) ejection channel (RL+CE channel), regardless of the CE ejection efficiency, αCE. Conversely, the results of the polytropic model strongly depend on the adopted value of αCE. We find DWDs produced from the RL+CE channel have comparable WD masses and the mass ratio distribution peaks at around 1. Based on the magnitude-limited sample of DWDs, the space densities for the detectable DWDs and those with extremely low-mass WD (ELM WD) companions in Ge’s model is: 1347 kpc−3 and 473 kpc−3, respectively, which is close to what has been shown in observations. On the other hand, the polytropic model overpredicts space density of DWDs by a factor of about 2-3. We also find that the results of DWD merger rate distribution per Galaxy in Ge’s model reproduce the obser

关键词： White dwarfs

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The First Photometric Analysis of Two Low Mass Ratio Contact Binary Systems In TESS Survey

arXiv

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arXiv 2024年

作者： Cheng, Qiyuan Xiong, Jianping Ding, Xu Ji, Kaifan Li, Jiao Liu, Chao Li, Jiangdan Luo, Jingxiao Lyu, Xin Han, Zhanwen Chen, Xuefei Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing100049 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 Key Laboratory of Space Astronomy and Technology National Astronomical Observatories CAS Beijing100101 China Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Beijing102206 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Key Laboratory of Radio Astronomy and Technolgoy Chinese Academy of Sciences A20 Datun Road Chaoyang District Beijing100101 China

Low mass-ratio (q) contact binary systems are progenitors of stellar mergers such as blue straggles (BS) or fast-rotating FK Com stars. In this study, we present the first light curve analysis of two newly identified low mass-ratio contact binary systems, TIC 55007847 and TIC 63597006, that are identified from TESS. Both stars are classified as A-subtype contact binaries. We obtained the precise orbit periods for the two objects by using the O-C method, i.e. P=0.6117108 d for TIC 55007847 and P=0.7008995 d for TIC 63597006, respectively, and found an obvious periodic signal in the O-C curve of TIC 63597006. We suggest that the periodic signal comes from a third body. We further use the Markov Chain Monte Carlo (MCMC) method with PHOEBE to derive the photometric solutions for the two binaries. The photometric solution for this object shows that the contribution of the third body is about 6%. Our analysis revealed that TIC 55007847 has an extremely low mass ratio of q = 0.08. By calculating the ratio of spin angular momentum to the orbital angular momentum Js/Jo, we found that TIC 55007847 is very close to the instability threshold with Js/Jo = 0.31, indicating that it may merge into a single, fast-rotating star in the future. For TIC 63597006, q = 0.14 and Js/Jo = 0.15. This object is in a relatively stable evolutionary status at present. Copyright © 2024, The Authors. All rights reserved.

关键词： Monte Carlo methods

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The effect of aspherical stellar wind of giant stars on the symbiotic channel of type Ia supernovae

arXiv

引用

arXiv 2021年

作者： Wu, Chengyuan Liu, Dongdong Wang, Xiaofeng Wang, Bo Tsinghua University Beijing100084 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Yunnan Observatories CAS Kunming650216 China University of Chinese Academy of Sciences Beijing100049 China

The progenitor systems accounting for explosions of type Ia supernovae (SNe Ia) is still under debate. Symbiotic channel is one of the possible progenitor scenarios, in which the WDs in these systems increase in mass through wind accretion from their red giant companions. The mass-loss processes of the giants in the symbiotic systems could produce amount of circumstellar medium (CSM), and the detections of the interaction signals between SN ejecta and CSM can be used as an ideal way to distinguish the different progenitor models. However, the density distribution and geometric structure of the CSM around the symbiotic systems remain highly uncertain. By assuming that the tidal torque from binary interaction can increase the mass-loss rate of the red giant and cause the stellar wind concentrate towards the equatorial plane, we provide a simplified method to estimate the density and the degree of deviation from spherical symmetry of the CSM. Based on the calculations of the binary evolutions of symbiotic systems using stellar evolution code MESA, we obtained the parameter space for producing SNe Ia. We found that SNe Ia could originate from symbiotic systems with massive carbon-oxygen white dwarfs (CO WDs), while the half-opening angle of the stellar wind from red giant towards the WD varies with the binary evolution, resulting in the formation of surrounding CSM with different geometric structures. The corresponding properties of ejecta-CSM interactions may be examined by the spectropolarimetry observations in the future, from which one may find additional relationship between circumstellar environment of SNe Ia and their progenitor systems. © 2021, CC0.

关键词： White dwarfs

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Hawking-like radiation of charged particles via tunneling across the lightcylinder of a rotating magnetosphere

arXiv

引用

arXiv 2021年

作者： Li, Huiquan 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

In rotating magnetospheres planted on compact objects, there usually exist light-cylinders (LC), beyond which the rotation speed of the magnetic field lines exceeds the speed of light. The LC is a close analog to the horizon in gravity, and is a casual boundary for charged particles that are restricted to move along the magnetic field lines. In this work, it is proposed that there should be Hawking-like radiation of charged particles from the LC of a rotating magnetosphere from the point of view of tunneling by using the field sheet metric. Copyright © 2021, The Authors. All rights reserved.

关键词： Charged particles

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Synchrotron polarization of a hybrid distribution of relativistic thermal and nonthermal electrons in GRB prompt emission

arXiv

引用

arXiv 2024年

作者： Cheng, Kangfa Mao, Jirong Zhao, Xiaohong Liu, Hongbang Kole, Merlin Produit, Nicolas Chen, Zhifu School of Mathematics and Physics 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 School of Physical Science and Technology Guangxi University Nanning530004 China Space Science Center University of New Hampshire DurhamNH03824 United States Astronomy Department University of Geneva Versoix Switzerland

Synchrotron polarization of relativistic nonthermal electrons in gamma-ray bursts (GRBs) has been widely studied. However, recent numerical simulations of relativistic shocks and magnetic reconnection have found that a more realistic electron distribution consists of a power-law component plus a thermal component, which requires observational validation. In this paper, we investigate synchrotron polarization using a hybrid energy distribution of relativistic thermal and nonthermal electrons within a globally toroidal magnetic field in GRB prompt emission. Our results show that, compared to the case of solely non-thermal electrons, the synchrotron polarization degrees (PDs) in these hybrid electrons can vary widely depending on different parameters and that the PD decreases progressively with frequency in the γ-ray, X-ray, and optical bands. The time-averaged PD spectrum displays a significant bump in the γ-ray and X-ray bands with the PDs higher than ∼ 60% if the thermal peak energy of electrons is much smaller than the conjunctive energy of electrons between the thermal and non-thermal distribution. The high synchrotron PD ( 60%) in the γ-ray and X-ray bands, which generally can not be produced by solely non-thermal electrons with typical power-law slopes, can be achieved by the hybrid electrons and primarily originates from the exponential decay part of the thermal component. Moreover, this model can roughly explain the PDs and spectral properties of some GRBs, where GRB 110301A with a high PD ((Equation presented)) may be potential evidence for the existence of relativistic thermal electrons. Copyright © 2024, The Authors. All rights reserved.

关键词： Gamma rays

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