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The Preliminary Statistical Analysis of LAMOST DR8 Low Resolution AFGK Stars

Research in Astronomy and Astrophysics 2022年第5期22卷 68-74页

作者： Y.H.Chen G.W.Li H.Shu Institute of Astrophysics Chuxiong Normal UniversityChuxiong 675000China School of Physics and Electronical Science Chuxiong Normal UniversityChuxiong 675000China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

We download the Large sky Area Multi-Object fiber Spectroscopic Telescope Data Release 8(LAMOST DR8)low resolution catalog for 6,478,063 AFGK type stars and plot the figures of effective temperature,gravitational acceleration and metal *** 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 *** analyze the observed statistical data and model calculation results,and then obtain some basic conclusions *** red giant and asymptotic giant branch stars with log g less than 0.85 have poor metal *** hot A type main-sequence stars are metal-rich stars with log g from 3.5 to *** conclusions are reasonable within a certain error *** theory of a gap area in the Hertzsprung-Russell diagram for stellar evolutions of medium mass stars is reflected in the statistical *** central core hydrogen burning stage and the central core helium burning stage correspond to the peak structures in the statistical plots for gravitational *** metal abundances among A,F,G and K type stars have a wide *** cannot simply replace the metal abundances of these stars with the metal abundance of the Sun when doing fine research work.

关键词： stars statistics-stars evolution-techniques spectroscopic

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Proper way to spatially decompose the gravitational-wave origin in stellar collapse simulations

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Physical Review D 2024年第8期110卷 083034页

作者： Shuai Zha Yunnan Observatories Chinese Academy of Sciences (CAS) Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects CAS Kunming 650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming 650216 China

Gravitational waves (GWs) hold great potential for an unobscured view of protoneutron stars (PNSs) formed as a result of stellar collapses. While waiting for discovery, deepening the understanding of GW emission in theory is beneficial for both optimizing searching strategies and deciphering the eventual data. One significant aspect is the spatially dependent contribution to the overall GW signal extracted from sophisticated hydrodynamic simulations. I present the proper way to perform the spatial decomposition of GW strain with the quadrupole formula in the slow-motion and weak-field approximation. Then I demonstrate the approach using the results of a 2D axisymmetric pseudo-Newtonian hydrodynamic simulation of core-collapse supernova. I show a detailed comparison between the proper and improper methods and discuss the possible consequences based on the improper method. Moreover, with the correct approach, the GW spatial profiles agree well with those calculated from a consistent perturbative method.

关键词： Gravitational wave sources Novae & supernovae Hydrodynamic models

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Type Ia Supernova Explosions in Binary Systems:A Review

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Research in Astronomy and Astrophysics 2023年第8期23卷 10-52页

作者： Zheng-Wei Liu Friedrich K.Röpke Zhanwen Han Yunnan Observatories Chinese Academy of Sciences(CAS)Kunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects CASKunming 650216China International Centre of Supernovae Yunnan Key LaboratoryKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Zentrum für Astronomie der Universität Heidelberg Institut für Theoretische AstrophysikPhilosophenweg 12D-69120 HeidelbergGermany Heidelberger Institut für Theoretische Studien Schloss-Wolfsbrunnenweg 35D-69118 HeidelbergGermany

Type Ia supernovae(SNe Ia)play a key role in the fields of astrophysics and *** is widely accepted that SNe Ia arise from thermonuclear explosions of white dwarfs(WDs)in binary ***,there is no consensus on the fundamental aspects of the nature of SN Ia progenitors and their actual explosion *** fundamentally flaws our understanding of these important astrophysical *** this review,we outline the diversity of SNe Ia and the proposed progenitor models and explosion *** discuss the recent theoretical and observational progress in addressing the SN Ia progenitor and explosion mechanism in terms of the observables at various stages of the explosion,including rates and delay times,pre-explosion companion stars,ejecta–companion interaction,early excess emission,early radio/X-ray emission from circumstellar material interaction,surviving companion stars,late-time spectra and photometry,polarization signals and supernova remnant *** the efforts from both the theoretical and observational sides,questions of how the WDs reach an explosive state and what progenitor systems are more likely to produce SNe Ia remain *** single published model is able to consistently explain all observational features and the full diversity of SNe *** may indicate that either a new progenitor paradigm or an improvement in current models is needed if all SNe Ia arise from the same *** alternative scenario is that different progenitor channels and explosion mechanisms contribute to SNe *** the next decade,the ongoing campaigns with the James Webb Space Telescope,Gaia and the Zwicky Transient Facility,and upcoming extensive projects with the Vera *** Observatory's Legacy Survey of Space and Time and the Square Kilometre Array will allow us to conduct not only studies of individual SNe Ia in unprecedented detail but also systematic investigations for different subclasses of SNe *** will advance theory and observation

关键词： (stars:)binaries(including multiple) close-methods numerical-(stars )supernovae general

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Spatially Resolved Properties of the GW170817 Host Galaxy

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Research in Astronomy and Astrophysics 2023年第7期23卷 80-95页

作者： Yubin Li Jirong Mao Jianbo Qin Xianzhong Zheng Fengshan Liu Yinghe Zhao Xiaohong Zhao Yunnan Observatories Chinese Academy of SciencesKunming 650011China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650011China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210023China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

GW170817 is the unique gravitational-wave(GW)event associated with the electromagnetic(EM)counterpart GRB *** 4993 is identified as the host galaxy of GW170817/GRB *** this paper,we focus on the spatially resolved properties of NGC *** present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical *** morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of a major galaxy *** spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas *** derive the merging rate of the compact object per galaxy by a co-evolution scenario of a supermassive black hole and its host *** the galaxy formation is at redshift 1.0,the merging rate per galaxy is from 3.2×10^(-4)to 7.7×10^(-5)within the merging decay time from 1.0 to 5.0 *** results provide vital information for ongoing GW EM counterpart *** Hubble space telescope data analysis presented in this paper can be also applied to Chinese Space Station Telescope research in the future.

关键词： galaxies:evolution (stars:)binaries:general gravitational waves

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New Simulations of the X-Ray Spectra and Polarizations of Accretion-disk Corona Systems with Various Geometrical Configurations *** Description

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Research in Astronomy and Astrophysics 2022年第8期22卷 140-158页

作者： Xiao-Lin Yang Jian-Cheng Wang Chu-Yuan Yang Yunnan Observatories Chinese Academy of Sciences396 YangfangwangKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Energetic X-ray radiations emitted from various accretion systems are widely considered to be produced by Comptonization in the hot *** corona and its interaction with the disk play an essential role in the evolution of the system and are potentially responsible for many observed ***,many intrinsic properties of the corona are still poorly understood,especially for the geometrical *** traditional spectral fitting method is not powerful enough to distinguish various *** this paper,we intend to investigate the possible configurations by modeling the polarization properties of X-ray *** geometries of the corona include the slab,sphere and *** simulations are implemented through the publicly available code,Lemon,which can deal with the polarized radiative transfer and different electron distributions *** results demonstrate clearly that the observed polarizations are dependent heavily on the geometry of the *** slab-like corona produces the highest polarization degrees(PDs),followed by the cylinder and *** of the interesting things is that the PDs first increase gradually and then decrease with the increase of photon *** slab geometry,there exists a zero-point where the polarization vanishes and the polarization angle(PA)rotates by 90°.These results may potentially be verified by the upcoming missions for polarized X-ray observations,such as IXPE and e XTP.

关键词： relativistic processes polarization X-rays:galaxies scattering radiation mechanisms:non-thermal

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V0644 Ser:An Active Ultrashort Period Contact Binary Star

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Research in Astronomy and Astrophysics 2022年第3期22卷 252-262页

作者： Hu-Shan Xu Li-Ying Zhu Sarotsakulchai Thawicharat Soonthornthum Boonrucksar Yunnan Observatories Chinese Academy of Sciences(CAS)Kunming 650216China University of the Chinese Academy of Sciences Beijing 100049China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China National Astronomical Research Institute of Thailand 191 Siriphanich Bldg.Huay Kaew Rd.Chiang Mai 50200Thailand

The photometric solutions of the ultrashort period close binary V0644 Ser based on our new complete BVRI light curves are derived by the Wilson–Devininney *** results show that V0644 Ser is a W-type shallow contact binary,and the third light was found in the R and I *** with the light curves in 2011,the amplitude variation of the secondary maximum can be explained by the temperature change from hot to cold in the local region of the star surface caused by magnetic activity or convective *** with the Gaia parallax,the absolute parameters of this system are obtained:M_(1)=0.29(4)M_(⊙),R_(1)=0.48(3)R_(⊙),R_(2)=0.65(3)R_(⊙),L_(1)=0.11(2)L_(⊙),L_(2)=0.16(2)L_(⊙)=0.16(2)L_(⊙).To study the period variation,we fitted the Super WASP,CSS,ASAS-SN and ZTF survey timing data to obtain light minima times spanning 14 *** O-C analysis,we find that the orbital period of this system has a long-term period decrease and periodic *** long-term period decrease can be explained by the mass transfer from more-massive component to less one and angular momentum loss via magnetic stellar *** the period decrease,this system is evolving from the present shallow contact phase to a relatively deeper stage predicted by the thermal relaxation oscillation *** oscillation can be explained by the light-time effect of the cool third *** third body may play an important role in the early formation and evolution of the binary system by removing angular momentum.

关键词： (stars:)binaries(including multiple):close (stars:)binaries:eclipsing stars:late-type stars:individual(V0644 Ser)

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AT2021acak:a Candidate Tidal Disruption Event Found in the Zwicky Transient Facility Survey

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Research in Astronomy and Astrophysics 2023年第2期23卷 163-171页

作者： Jie Li Zhong-Xiang Wang Dong Zheng Ju-Jia Zhang Li-Tao Zhu Zhang-Yi Chen Department of Astronomy School of Physics and AstronomyYunnan UniversityKunming 650091China Purple Mountain Observatory Chinese Academy of SciencesNanjing 210034China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Center for Astronomical Mega-Science Chinese Academy of SciencesBejing 100101China

We report a candidate tidal disruption event(TDE) found in the Zwicky Transient Facility survey *** candidate,with its transient name AT2021acak,showed brightness increases of ~1 mag around MJD 59500 and subsequent power-law–like brightness *** have conducted multiple optical spectroscopic observations with the 2.4 m Lijiang telescope and one observation at X-ray and ultraviolet(UV) bands with the Neil Gehrels Swift Observatory(Swift).The optical spectra of the source show broad H and He emission lines and Fe emission *** 0.3–2 ke V X-ray and bright UV emission of the source was *** analyze the declines of the optical light curves,the emission features of the optical spectra,and the constructed broad-band UV and optical *** properties derived from the analyses are consistent with those of reported(candidate) TDEs,and in particular very similar to those of *** identification is complicated by the host being likely an AGN,and thus further observations of the event and quiescent host are required in order to have a clear understanding of the nature of this transient event.

关键词： galaxies nuclei-galaxies active-(galaxies:)quasars general

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Astrometric Observations of NEA 1998 HH49 Using the Daocheng 50 cm Telescope

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Research in Astronomy and Astrophysics 2024年第7期24卷 71-78页

作者： Huan Xu Xiang-Ming Cheng Yi-Gong Zhang Teng-Fei Song Zhen-Jun Zhang Qing-Yu Peng Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China Engineering Laboratory on Applied Astronomical Technology of Yunnan Kunming 650216China School of Information Engineering Kunming UniversityKunming 650214China School of Computer Science and Information Engineering Anyang Institute of TechnologyAnyang 455000China Department of Computer Science Jinan UniversityGuangzhou 510632China Sino-French Joint Laboratory for Astrometry Dynamics and Space ScienceJinan UniversityGuangzhou 510632China

This study details an astrometric observation campaign of the Near-Earth Asteroid 1998 HH49,conducted with the aim of refining our understanding of its physical *** the 50 cm telescope located at the Wumingshan Mountain in Daocheng,Sichuan,images were obtained over four nights,from 2023 October 19 to October *** observations were processed using Astrometrica software,facilitating the precise determination of the asteroid's *** observational results were compared with the ephemerides from three distinct sources to verify accuracy:the Jet Propulsion laboratory(JPL)Horizons System,the Institut de Mécanique Céleste et de Calcul deséphémérides(IMCCE)Miriade,and the Near-Earth objects Dynamic Site(NEODyS-2).When compared with the JPL ephemeris,a mean observed-minus-calculated(O-C)result of 0.″07 in the *** and-0.″35 in the *** was ***,the comparison with the IMCCE ephemeris yielded mean O-C results of 0.″08 in the *** and-0.″06 in the *** comparison with the NEODyS-2 ephemeris yielded the mean O-C results of 0.″06 in ***-0.″49 in *** study's findings demonstrate a general consistency between the observed data and the ephemeris predictions,with minor discrepancies observed across the data ***,both the JPL and NEODyS-2 ephemerides show that the residuals in the *** exceed those in the *** disparities may result from atmospheric differential color refraction,ephemeris discrepancies,observational errors,and other ***,it is worth noting that further investigation is required due to the potential influence of additional ***,the Daocheng 50 cm Telescope exhibits the ability to conduct high-precision positional measurements.

关键词： astrometry ephemerides time

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Mass Transfer Physics in Binary Stars and Applications in Gravitational Wave Sources

arXiv

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arXiv 2024年

作者： Ge, Hongwei Han, Zhanwen Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China

The stability criteria of rapid mass transfer and common-envelope evolution are fundamental in binary star evolution. They determine the mass, mass ratio, and orbital distribution of many important systems, such as X-ray binaries, type Ia supernovae, and merging gravitational-wave sources. In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We built the adiabatic mass-loss model and systematically surveyed the thresholds for dynamical timescale mass transfer over the entire span of possible donor star evolutionary states. Many studies indicate that new mass transfer stability thresholds play an essential role in the formation and properties of double compact object populations and the progenitors of SNe Ia and detectable GW sources. For example, our studies show that the mass transfer in the red giant and the asymptotic giant branch stars and the massive stars can be more stable than previously believed. Consequently, detailed binary population synthesis studies, using updated unstable mass transfer criteria, predicate the non-conservative stable mass transfer may dominate the formation channel of double stellar-mass black holes and can explain the population of the large mass ratio double stellar-mass black holes. Using our updated mass transfer thresholds, binary population thesis studies by Li et al. show that Ge et al.’s results support the observational double white dwarfs merger rate distribution per Galaxy and the space density of double white dwarfs in the Galaxy. Copyright © 2024, The Authors. All rights reserved.

关键词： White dwarfs

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One model to rule them all: magnetic braking from CVs to low-mass stars 6

One model to rule them all: magnetic braking from CVs to low...

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6th Golden Age of Cataclysmic Variables and Related objects, GOLDEN 2023

作者： Sarkar, Arnab Ge, Hongwei Yungelson, Lev Tout, Christopher A. Institute of Astronomy University of Cambridge The Observatories Madingley Road CambridgeCB3 OHA United Kingdom Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Key Laboratory for Structure and Evolution of Celestial Objects CAS Kunming650216 China International Centre of Supernovae Yunnan Key Laboratory Kunming650216 China Institute of Astronomy The Russian Academy of Sciences 48 Pyatnitskaya Str. Moscow119017 Russia

We present the results of the study of the secular evolution of donor stars in cataclysmic variables (CVs) and AM Canum Venaticorum (AM CVn) stars with our double dynamo (DD) formalism of angular momentum loss (AML) by magnetic braking (MB). In our DD model, MB is driven by an interplay between two a − Ω dynamos, one in the convective envelope and the other at the boundary of the radiative core and the convective envelope. We show that (1) our MB model reproduces the period gap (2 Porb/ hr 3) and the period minimum spike (Porb ≈ 80 min) in the distribution of non-magnetic CVs, (2) evolved CVs, where the donor star commences Roche lobe overflow (RLOF) close to or just beyond the end of the main-sequence, populate the region in and beyond the period gap, and are more likely to be detected at Porb ≥ 5.5 hr. This likely contaminates the mass-radius fit of long-period CV donors. We show that (3) some of the evolved CVs become AM CVn stars with 10 Porb/ min 65. Their evolution, driven by AMLMB and AML by gravitational radiation (GR, AMLGR), leaves them extremely H-exhausted to the point of being indistinguishable from AM CVn systems formed via the He-star and the White Dwarf (WD) channels in terms of the absence of H in their spectra. We further show that (4) owing to the presence of a significant radiative region, intermediate-mass giants/sub-giants, which are progenitors of AM CVn stars formed through the He-star channel, may undergo common envelope evolution that does not behave classically, (5) several AM CVn systems with extremely bloated donors, such as Gaia14aae, ZTFJ1637+49 and SRGeJ045359.9+622444 do not match any modelled trajectories if these systems are modelled only with AMLGR without incorporating AMLMB, (6) the uncertainties in MB estimates greatly affect modelling results. This, in turn, affects our efforts to distinguish between different AM CVn formation channels and their relative importance. Finally, we find that (7) a similar MB prescription also expl

关键词： White dwarfs

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