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Prominence activation, optical flare, and post-flare loops on the RS Canum Venaticorum star SZ Piscium

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arXiv 2024年

作者： Cao, Dongtao Gu, Shenghong Ge, Jian Wang, Tinggui Zhou, Jilin Chang, Liang Wolter, U. Mittag, M. Schmitt, J.H.M.M. Perdelwitz, V. 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 Department of Astronomy University of Florida Bryant Space Science Center GainesvilleFL32611 United States Key Laboratory for Research in Galaxies and Cosmology Department of Astronomy University of Science and Technology of China Chinese Academy of Sciences Hefei230026 China Department of Astronomy Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education Nanjing University Nanjing210093 China Hamburger Sternwarte Universität Hamburg Hamburg21029 Germany

We present the results of time-resolved high-resolution spectroscopic observations of the very active RS Canum Venaticorum (RS CVn) star SZ Piscium (SZ Psc), obtained during two consecutive observing nights on October 24 and 25, 2011. Several optical chromospheric activity indicators are analyzed using the spectral subtraction tech- nique, which show the remarkably different behavior between two nights. Gradually blue-shifted and strengthened excess absorption features presented in the series of the subtracted spectra (especially for the Hα, He i D3 and Hβ lines), as a result of active stellar prominence that is rising its height along the line of our sight, was detected in the observations on October 24. This prominence activation event was probably associated with the subsequently occurred optical flare, and part of that flare decay phase was hunted in the observations on October 25. The flare was characterized by the prominent He i D3 line emission, as well as stronger chromospheric emission in the Hα, Hβ and other active lines. The gradual decay of flare was accompanied by an obviously developmental absorption feature in the blue wing of the H_ and other active lines, which could be explained as cool post-flare loops which projected against the bright flare background. Therefore, a series of possibly associated magnetic activity phenomena, including flare-related prominence activation, optical flare and post-flare loops, were detected during our observations. Copyright © 2024, The Authors. All rights reserved.

关键词： Chemical activation

Timing and spectral analysis of GK Persei during the 2010 dwarf nova outburst

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arXiv 2025年

作者： Pei, Songpeng Zhang, Xiaowan Li, Qiang Ou, Ziwei Yang, Taozhi Cai, Yongzhi School of Physics and Electrical Engineering Liupanshui Normal University Guizhou Liupanshui553004 China Qiannan Normal University for Nationalities Duyun558000 China Qiannan Key Laboratory of Radio Astronomy Guizhou Province Duyun558000 China Tsung-Dao Lee Institute Shanghai Jiao Tong University Shanghai201210 China Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter School of Physics Xi’an Jiaotong University Xi’an710049 China Yunnan Observatories Chinese Academy of Sciences 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

GK Persei, an old nova and intermediate polar (IP), exhibited a dwarf nova (DN) outburst in 2010. This outburst was extensively observed by the Neil Gehrels Swift Observatory, beginning 1.95 days after the eruption and continuing until 13.9 days before the maximum of the outburst in the optical. In this paper, we present timing and spectral analyses, comparing the results with those of other outbursts. We confirm the spin modulation in the 2 − 10 keV X-ray range with a period of PWD = 351.325(9) s. Additionally, we detected spin modulation in the 0.3 − 2 keV band during the second half of the observations, a feature not seen in the 2015 and 2018 outbursts. This finding suggests that the soft X-ray emission in GK Per may originate partly near the magnetic poles and partly from a wind or circumstellar material. Copyright © 2025, The Authors. All rights reserved.

关键词： Spectrum analyzers

A photometric study of the high-mass-ratio contact binary AV Puppis

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Research in Astronomy and Astrophysics 2019年第12期19卷 217-222页

作者： Quan-Wang Han Li-Fang Li Deng-Kai Jiang Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of Sciences.Kunming 650216China University of Chinese Academy of Sciences Beijing 100049China

The multi-color photometric light curves for contact binary AV Puppis(AV Pup) in VRcIc bandpasses are presented and analyzed by using the 2013 version of the Wilson-Devinney(W-D) *** solutions suggest that AV Pup is a peculiar A-subtype W UMa contact binary with a high mass ratio(q = m2/m1 = 0.896) and a low fill-out factor(f = 10%). Combining our newly determined times of minimum with those collected from literatures, the orbital period changes of this system are investigated. The O-C analysis indicates that the orbital period of AV Pup is increasing at a rate of d P/dt = 4.83 × 10-7 days yr-1, which can be explained by mass transfer from the less massive component to the more massive one.

关键词： techniques:photometric stars:magnetic field stars:individual:AV Pupis

The Common Envelope evolution Outcome-A Case Study on Hot Subdwarf B Stars

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arXiv 2022年

作者： Ge, Hongwei Tout, Christopher A. Chen, Xuefei Kruckow, Matthias U. Chen, Hailiang Jiang, Dengkai Li, Zhenwei Liu, Zhengwei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences 396 YangFangWang Guandu District Kunming650216 China Institute of Astronomy The Observatories University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Key Laboratory for Structure and Evolution of Celestial Objects Chinese Academy of Sciences P.O. Box 110 Kunming650216 China

Common envelope evolution (CEE) physics plays a fundamental role in the formation of binary systems, such as mergering stellar gravitational wave sources, pulsar binaries and type Ia supernovae. A precisely constrained CEE has become more important in the age of large surveys and gravitational wave detectors. We use an adiabatic mass loss model to explore how the total energy of the donor changes as a function of the remnant mass. This provides a more self-consistent way to calculate the binding energy of the donor. For comparison, we also calculate the binding energy through integrating the total energy from the core to the surface. The outcome of CEE is constrained by total energy conservation at the point at which both component's radii shrink back within their Roche lobes. We apply our results to 142 hot subdwarf binaries. For shorter orbital period sdBs, the binding energy is highly consistent. For longer orbital period sdBs in our samples, the binding energy can differ by up to a factor of 2. The CE efficiency parameter βCEbecomes smaller than αCEfor the final orbital period log10Porb=d >-0.5. We also find the mass ratios log10q and CE efficiency parameters log10αCEand log10βCElinearly correlate in sdBs, similarly to De Marco et al. (2011) for post-AGB binaries. © 2022, CC0.

关键词： Binding energy

Further study of starspot activity and measurement of differential rotation for SZ Piscium

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arXiv 2024年

作者： Xiang, Yue Gu, Shenghong Cameron, Collier Barnes, J.R. Cao, Dongtao Yunnan Observatories Chinese Academy of Sciences Kunming650216 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 School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing101408 China School of Physics and Astronomy University of St Andrews FifeKY16 9SS United Kingdom Department of Physical Sciences The Open University Walton Hall Milton KeynesMK7 6AA United Kingdom

We present a series of 9 Doppler images of the magnetically active K component of the RS CVn-type binary SZ Psc, based on the high-resolution spectroscopic data collected from 2014 to 2018. We apply least-squares deconvolution to all spectra to extract the average profiles with high signal-to-noise ratios (SNRs) for Doppler imaging. The surface maps of the K subgiant show starspots widely distributed along latitude and longitude. A prominent, non-axisymmetric polar spot around phase 0 is revealed by all images with sufficient phase coverage, which may be a stable feature on the K component. The starspots evolve in a time scale of one month. We have determined the surface shear rate of the K component from the starspot maps reconstructed 10 days apart in 2017 Nov–Dec, through the cross-correlation method. The surface differential rotation parameters are Ωeq = 1.591±0.002 rad d−1 and ΔΩ = 0.035±0.003 rad d−1. The absorption lines contributed from the tertiary component are detected in all LSD profiles of SZ Psc, and we measure the radial velocity of the binary system and the tertiary component to derive an elliptical orbit with a period of 1530 ± 3 days and a mass of 0.75 ± 0.06 M☉ for the tertiary component. Copyright © 2024, The Authors. All rights reserved.

关键词： Shear flow

The preliminary statistical analysis of LAMOST DR8 low resolution AFGK stars

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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

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

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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

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

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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

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

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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