Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Comp...Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Compact objects in binaries with a luminous stellar companion are perfect targets for optical observations.Candidate compact objects can be achieved by monitoring the radial velocities of the companion star.However,most of the spectroscopic telescopes usually obtain stellar spectra at a relatively low efficiency,which makes a sky survey for millions of stars practically impossible.The efficiency of a large-scale spectroscopic survey,the Large Sky Area Multi-Object Fiber Spectroscopy Telescope(LAMOST),presents a specific opportunity to search for compact object candidates,i.e.,simply from the spectroscopic observations.Late-type K/M stars are the most abundant populations in our Galaxy.Owing to the relatively large Keplerian velocities in the close binaries with a K/M-dwarf companion,a hidden compact object could be discovered and followed-up more easily.In this study,compact object candidates with K/Mdwarf companions are investigated with the LAMOST low-resolution stellar spectra.Based on the LAMOST Data Release 5,we obtained a sample of 56 binaries,each containing a K/M-dwarf with a large radial velocity variation △VR>150 km s^(-1).Complemented with the photometric information from the Transiting Exoplanet Survey Satellite,we derived a sample of 35 compact object candidates,among which,the orbital periods of 16 sources were revealed by the light curves.Considering two sources as examples,we confirmed that a compact object existed in the two systems by fitting the radial velocity curve.This study demonstrates the principle and the power of searching for compact objects through LAMOST.展开更多
The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs...The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.展开更多
This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V4...This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V455 And were obtained at the 6-m BTA of the SAO RAS in the low state of these systems with the determination of white dwarf radiation.The theoretical spectra were calculated using the grid models of hydrogen dwarf atmospheres of white dwarfs by varying the parameters(T_(eff) and log g) to reach the best agreement with the observed ones.We highlight different effects of the parameters on the shape and intensity of the HI lines.Therefore,it is possible to unambiguously determine T_(eff) and log g from the analysis of observations.The fundamental parameters of white dwarfs(M and R) were found by comparing the parameters of atmospheres with theoretical models of the internal structure.The obtained parameters of the primaries of TY Psc,FL Psc and V455 And are consistent with the average values for SU UMa and WZ Sge systems.As a result,we demonstrate the efficiency of the method for determining the parameters of such systems based on the analysis of a limited set of observed optical spectra.展开更多
Twenty-five typical massive white dwarfs(WDs)are selected and the proton decay reaction catalyzed by magnetic monopoles(MMs)for these WDs is discussed.A velocity-dependent correction factor strongly affects the cross-...Twenty-five typical massive white dwarfs(WDs)are selected and the proton decay reaction catalyzed by magnetic monopoles(MMs)for these WDs is discussed.A velocity-dependent correction factor strongly affects the cross-section.We find that a strong suppression controls the monopole catalysis of nucleon decay by the correction factor.The maximum number of MMs is captured and the luminosity can be 2.235×10^(21)and 1.7859×10^(32)erg s^(-1)(e.g.,for the O+Ne core mass WD J055631.17+130639.78).The luminosities of most massive WDs agree well with the observations at relatively low temperatures(e.g.,T_(6)=0.1),but can be three and two orders of magnitude higher than those of the observations for model(Ⅰ)and(Ⅱ)at relatively high temperatures(e.g.,T_(6)=10),respectively.The luminosities of model(Ⅰ)are about one order of magnitude higher than those of model(Ⅱ).Since we consider the effect of the number of MMs captured on the mass–radius relation and the suppression of the proton decay by the correction factor,the study by model(Ⅱ)may be an improved estimation.展开更多
The final outcomes of accreting ONe white dwarfs（ONe WDs） have been studied for several decades,but there are still some issues that are not resolved. Recently,some studies suggested that the deflagration of oxygen ...The final outcomes of accreting ONe white dwarfs（ONe WDs） have been studied for several decades,but there are still some issues that are not resolved. Recently,some studies suggested that the deflagration of oxygen would occur for accreting ONe WDs with Chandrasekhar masses. In this paper,we aim to investigate whether ONe WDs can experience accretion-induced collapse（AIC） or explosions when their masses approach the Chandrasekhar limit. Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics（MESA）,we simulate the longterm evolution of ONe WDs with accreting CO material. The ONe WDs undergo weak multicycle carbon flashes during the mass-accretion process,leading to mass increase of the WDs. We found that different initial WD masses and mass-accretion rates influence the evolution of central density and temperature. However,the central temperature cannot reach the explosive oxygen ignition temperature due to neutrino cooling. This work implies that the final outcome of accreting ONe WDs is electroncapture induced collapse rather than thermonuclear explosion.展开更多
据英国 New Scientist,2005,185(2486):12报道,美国一天文观测小组用斯皮泽空间望远镜拍摄到了一褐矮星周围的原行星盘,于2005年2月报告了他们的观测结果,并认为褐矮星周围能够出现适合生命演化的行星。褐矮星是质量介于木星的15至70倍...据英国 New Scientist,2005,185(2486):12报道,美国一天文观测小组用斯皮泽空间望远镜拍摄到了一褐矮星周围的原行星盘,于2005年2月报告了他们的观测结果,并认为褐矮星周围能够出现适合生命演化的行星。褐矮星是质量介于木星的15至70倍之间的星体,即质量不及太阳8%的星,故其内部不能连续地产生氢核聚变反应以提供发光能源,但它们和普通恒星一样。展开更多
中国空间站工程巡天望远镜(China Space Station Telescope,CSST)计划于2024年发射,将主要开展高空间分辨率、天区大面积(约17500平方度)的多色成像与无缝光谱巡天,预计可极大地提高白矮星的观测样本数量.本文分别基于盖亚第三次早期数...中国空间站工程巡天望远镜(China Space Station Telescope,CSST)计划于2024年发射,将主要开展高空间分辨率、天区大面积(约17500平方度)的多色成像与无缝光谱巡天,预计可极大地提高白矮星的观测样本数量.本文分别基于盖亚第三次早期数据发布(Gaia EDR3)和斯隆数字巡天第十六次数据发布(SDSS DR16)探测到的白矮星候选体和已确认的白矮星样本,进行统计分析,得出恒星参数的分布(多波段星等、有效温度、表面重力加速度、距离和质量),并分析各参数之间的相关性,计算白矮星的空间密度;最后,结合CSST的观测性能,预计其将探测到的白矮星数目,为基于CSST主巡天数据开展大样本暗弱白矮星搜寻和研究工作提供预估和分析.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12103047,11925301,12033006,12005192)the National Key Research and Development Program of China(Grant No.2019YFA0405000)+2 种基金the China Manned Space Project(Grant No.CMS-CSST-2021-B07)the China Postdoctoral Science Foundation(Grant Nos.2019TQ0288,2020TQ0287,2020M672255,2021M702742)the Natural Science Foundation of Henan Province of China(Grant No.212300410290)。
文摘Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Compact objects in binaries with a luminous stellar companion are perfect targets for optical observations.Candidate compact objects can be achieved by monitoring the radial velocities of the companion star.However,most of the spectroscopic telescopes usually obtain stellar spectra at a relatively low efficiency,which makes a sky survey for millions of stars practically impossible.The efficiency of a large-scale spectroscopic survey,the Large Sky Area Multi-Object Fiber Spectroscopy Telescope(LAMOST),presents a specific opportunity to search for compact object candidates,i.e.,simply from the spectroscopic observations.Late-type K/M stars are the most abundant populations in our Galaxy.Owing to the relatively large Keplerian velocities in the close binaries with a K/M-dwarf companion,a hidden compact object could be discovered and followed-up more easily.In this study,compact object candidates with K/Mdwarf companions are investigated with the LAMOST low-resolution stellar spectra.Based on the LAMOST Data Release 5,we obtained a sample of 56 binaries,each containing a K/M-dwarf with a large radial velocity variation △VR>150 km s^(-1).Complemented with the photometric information from the Transiting Exoplanet Survey Satellite,we derived a sample of 35 compact object candidates,among which,the orbital periods of 16 sources were revealed by the light curves.Considering two sources as examples,we confirmed that a compact object existed in the two systems by fitting the radial velocity curve.This study demonstrates the principle and the power of searching for compact objects through LAMOST.
基金supported by the National Natural Science Foundation of China through Grant 11873029the National Key Research and Development Program of China(2016YFA0400803 and 2017YFA0402703)。
文摘The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.
基金supported by the Ministry of Science and Higher Education of the Russian Federationfinancial support from the RFBR and the Government of the RT in the framework of scientific projects 18–42–160003funded by the subsidy 671–2020–0052 allocated to KFU for assignment in scientific activities。
文摘This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V455 And were obtained at the 6-m BTA of the SAO RAS in the low state of these systems with the determination of white dwarf radiation.The theoretical spectra were calculated using the grid models of hydrogen dwarf atmospheres of white dwarfs by varying the parameters(T_(eff) and log g) to reach the best agreement with the observed ones.We highlight different effects of the parameters on the shape and intensity of the HI lines.Therefore,it is possible to unambiguously determine T_(eff) and log g from the analysis of observations.The fundamental parameters of white dwarfs(M and R) were found by comparing the parameters of atmospheres with theoretical models of the internal structure.The obtained parameters of the primaries of TY Psc,FL Psc and V455 And are consistent with the average values for SU UMa and WZ Sge systems.As a result,we demonstrate the efficiency of the method for determining the parameters of such systems based on the analysis of a limited set of observed optical spectra.
基金supported in part by the National Natural Science Foundation of China(NSFC,grant Nos.11965010 and 11565020)the foundation for high-level talents program of Hainan basic and applied basic research program(natural science)under grant 2019RC239+3 种基金the Natural Science Foundation of Hainan Province under grants 118MS071 and 114012the Counterpart Foundation of Sanya under grants 2016PT43 and 2019PT76the Special Foundation of Science and Technology Cooperation for Advanced Academy and Regional of Sanya under grant 2016YD28the Scientific Research Starting Foundation for 515 Talented Project of Hainan Tropical Ocean University under grant RHDRC201701。
文摘Twenty-five typical massive white dwarfs(WDs)are selected and the proton decay reaction catalyzed by magnetic monopoles(MMs)for these WDs is discussed.A velocity-dependent correction factor strongly affects the cross-section.We find that a strong suppression controls the monopole catalysis of nucleon decay by the correction factor.The maximum number of MMs is captured and the luminosity can be 2.235×10^(21)and 1.7859×10^(32)erg s^(-1)(e.g.,for the O+Ne core mass WD J055631.17+130639.78).The luminosities of most massive WDs agree well with the observations at relatively low temperatures(e.g.,T_(6)=0.1),but can be three and two orders of magnitude higher than those of the observations for model(Ⅰ)and(Ⅱ)at relatively high temperatures(e.g.,T_(6)=10),respectively.The luminosities of model(Ⅰ)are about one order of magnitude higher than those of model(Ⅱ).Since we consider the effect of the number of MMs captured on the mass–radius relation and the suppression of the proton decay by the correction factor,the study by model(Ⅱ)may be an improved estimation.
基金supported by the National Basic Research Program of China (973 program,2014CB845700)the Chinese Academy of Sciences (Nos.KJZD-EW-M06-01 and QYZDBSSW-SYS001)+1 种基金the National Natural Science Foundation of China (Nos.11673059,11521303,11390374 and 11573016)the Natural Science Foundation of Yunnan Province (Nos.2013HB097,2013HA005 and 2017HC018)
文摘The final outcomes of accreting ONe white dwarfs（ONe WDs） have been studied for several decades,but there are still some issues that are not resolved. Recently,some studies suggested that the deflagration of oxygen would occur for accreting ONe WDs with Chandrasekhar masses. In this paper,we aim to investigate whether ONe WDs can experience accretion-induced collapse（AIC） or explosions when their masses approach the Chandrasekhar limit. Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics（MESA）,we simulate the longterm evolution of ONe WDs with accreting CO material. The ONe WDs undergo weak multicycle carbon flashes during the mass-accretion process,leading to mass increase of the WDs. We found that different initial WD masses and mass-accretion rates influence the evolution of central density and temperature. However,the central temperature cannot reach the explosive oxygen ignition temperature due to neutrino cooling. This work implies that the final outcome of accreting ONe WDs is electroncapture induced collapse rather than thermonuclear explosion.
文摘据英国 New Scientist,2005,185(2486):12报道,美国一天文观测小组用斯皮泽空间望远镜拍摄到了一褐矮星周围的原行星盘,于2005年2月报告了他们的观测结果,并认为褐矮星周围能够出现适合生命演化的行星。褐矮星是质量介于木星的15至70倍之间的星体,即质量不及太阳8%的星,故其内部不能连续地产生氢核聚变反应以提供发光能源,但它们和普通恒星一样。
文摘中国空间站工程巡天望远镜(China Space Station Telescope,CSST)计划于2024年发射,将主要开展高空间分辨率、天区大面积(约17500平方度)的多色成像与无缝光谱巡天,预计可极大地提高白矮星的观测样本数量.本文分别基于盖亚第三次早期数据发布(Gaia EDR3)和斯隆数字巡天第十六次数据发布(SDSS DR16)探测到的白矮星候选体和已确认的白矮星样本,进行统计分析,得出恒星参数的分布(多波段星等、有效温度、表面重力加速度、距离和质量),并分析各参数之间的相关性,计算白矮星的空间密度;最后,结合CSST的观测性能,预计其将探测到的白矮星数目,为基于CSST主巡天数据开展大样本暗弱白矮星搜寻和研究工作提供预估和分析.
