Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so f...Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so far is limited,and the reasons for their formation are still unclear.This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features.Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods.Among them,the results of 11 OCs are reliable as the observed CMDs are well-reproduced.We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies.The results also show that the impact of age spread is important,as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.展开更多
We present an updated catalog of 46,753 radial velocity(RV)standard stars selected from the APOGEE DR17.These stars cover the Northern and Southern Hemispheres almost evenly,with 62%being red giants and 38%being main ...We present an updated catalog of 46,753 radial velocity(RV)standard stars selected from the APOGEE DR17.These stars cover the Northern and Southern Hemispheres almost evenly,with 62%being red giants and 38%being main sequence stars.These RV standard stars are stable on a baseline longer than 200 days(with 54%longer than one year and 10%longer than five years)with a median stability better than 215 m s~(-1).The average number of observations of those stars is 5 and each observation is required to have signal-to-noise ratio greater than50 and RV measurement error smaller than 500 m s~(-1).Based on the new APOGEE RV standard star catalog,we have checked the RV zero-points(RVZPs)for current large-scale stellar spectroscopic surveys including RAVE,LAMOST,GALAH and Gaia.By careful analysis,we estimate their mean RVZP to be+0.149 kms~(-1),+4.574 km s~(-1)(for LRS),-0.031 km s~(-1)and+0.014 kms~(-1),respectively,for the four surveys.In the RAVE,LAMOST(for MRS),GALAH and Gaia surveys,RVZP exhibits a systematic trend with stellar parameters(mainly[Fe/H],T_(eff),log g,G_(BP)-G_(RP)and G_(RVS)).The corrections to those small but clear RVZPs are of vital importance for these massive spectroscopic surveys in various studies that require extremely high RV accuracies.展开更多
GW170817 is the unique gravitational-wave(GW)event associated with the electromagnetic(EM)counterpart GRB 170817A.NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A.In this paper,we focus on the spatial...GW170817 is the unique gravitational-wave(GW)event associated with the electromagnetic(EM)counterpart GRB 170817A.NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A.In this paper,we focus on the spatially resolved properties of NGC 4993.We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands.The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of a major galaxy merger.The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion.We derive the merging rate of the compact object per galaxy by a co-evolution scenario of a supermassive black hole and its host galaxy.If 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 Gyr.The results provide vital information for ongoing GW EM counterpart detections.The Hubble space telescope data analysis presented in this paper can be also applied to Chinese Space Station Telescope research in the future.展开更多
Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a ~2–5 M⊙mass gap between the most massive neutron stars and the least massive black holes, while some recent evidenc...Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a ~2–5 M⊙mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears to support that this mass gap is being populated. Whether there is a mass gap or not can potentially shed light on the physics of supernova explosions that form neutron stars and black holes, although significant mass accretion of neutron stars including binary mergers may lead to the formation of mass-gap objects. In this review, I collect the compact objects that are probable black holes with masses being in the gap. Most of them are in binaries, their mass measurements are obviously subject to some uncertainties. Current observations are still unable to confidently infer an absence or presence of the mass gap. Ongoing and future surveys are expected to build the mass spectrum of black holes which can be used to constrain the process of their formation especially in binaries. I describe the theoretical predictions for the formation of black holes in various types of binaries, and present some prospects of searching for black holes via electromagnetic and gravitational wave observations.展开更多
I review studies of core collapse supernovae(CCSNe) and similar transient events that attribute major roles to jets in powering most CCSNe and in shaping their ejecta. I start with reviewing the jittering jets explosi...I review studies of core collapse supernovae(CCSNe) and similar transient events that attribute major roles to jets in powering most CCSNe and in shaping their ejecta. I start with reviewing the jittering jets explosion mechanism that I take to power most CCSN explosions. Neutrino heating does play a role in boosting the jets. I compare the morphologies of some CCSN remnants to planetary nebulae to conclude that jets and instabilities are behind the shaping of their ejecta. I then discuss CCSNe that are descendants of rapidly rotating collapsing cores that result in fixed-axis jets(with small jittering) that shape bipolar ejecta. A large fraction of the bipolar CCSNe are superluminous supernovae(SLSNe). I conclude that modeling of SLSN light curves and bumps in the light curves must include jets, even when considering energetic magnetars and/or ejecta interaction with the circumstellar matter(CSM). I connect the properties of bipolar CCSNe to common envelope jets supernovae(CEJSNe) where an old neutron star or a black hole spirals-in inside the envelope and then inside the core of a red supergiant. I discuss how jets can shape the pre-explosion CSM, as in Supernova 1987A, and can power pre-explosion outbursts(precursors)in binary system progenitors of CCSNe and CEJSNe. Binary interaction also facilitates the launching of postexplosion jets.展开更多
We study the origin of the UV-excess in star clusters by performing N-body simulations of six clusters with N = 10 k and N = 100 k(single stars & binary systems) and metallicities of Z = 0.01, 0.001 and 0.0001, us...We study the origin of the UV-excess in star clusters by performing N-body simulations of six clusters with N = 10 k and N = 100 k(single stars & binary systems) and metallicities of Z = 0.01, 0.001 and 0.0001, using PETAR. All models initially have a 50% primordial binary fraction. Using Galev NB we convert the simulated data into synthetic spectra and photometry for the China Space Station Telescope(CSST) and Hubble Space Telescope(HST). From the spectral energy distributions we identify three stellar populations that contribute to the UVexcess:(1) second asymptotic giant branch stars, which contribute to the UV flux at early times;(2) naked helium stars and(3) white dwarfs, which are long-term contributors to the FUV spectra. Binary stars consisting of a white dwarf and a main sequence star are cataclysmic variable(CV) candidates. The magnitude distribution of CV candidates is bimodal up to 2 Gyr. The bright CV population is particularly bright in FUV-NUV. The FUV-NUV color of our model clusters is 1–2 mag redder than the UV-excess globular clusters in M87 and in the Milky Way. This discrepancy may be induced by helium enrichment in observed clusters. Our simulations are based on simple stellar evolution;we do not include the effects of variations in helium and light elements or multiple stellar populations. A positive radial color gradient is present in CSST NUV-y for main sequence stars in all models with a color difference of 0.2–0.5 mag, up to 4 half-mass radii. The CSST NUV-g color correlates strongly with HST FUV-NUV for NUV-g > 1 mag, with the linear relation FUV-NUV =(1.09 ± 0.12) ×(NUV-g) +(-1.01 ± 0.22). This allows for conversion of future CSST NUV-g colors into HST FUV-NUV colors, which are sensitive to UV-excess features. We find that CSST will be able to detect UVexcess in Galactic/extragalactic star clusters with ages >200 Myr.展开更多
This paper presents a database of the spectroscopic-and photometric-spectral energy distributions(spec-SEDs and phot-SEDs respectively)of the progenitors of core-collapse supernovae(CCSNe).Both binary-and single-star ...This paper presents a database of the spectroscopic-and photometric-spectral energy distributions(spec-SEDs and phot-SEDs respectively)of the progenitors of core-collapse supernovae(CCSNe).Both binary-and single-star progenitors are included in the database.The database covers the initial metallicity(Z)range of 0.0001-0.03,mass range of 8-25 M⊙,binary mass ratio range of 0-1,and orbital period range of 0.1-10000 d.The low-resolution spec-SEDs and phot-SEDs of single-and binary-star CCSN progenitors are included in the database.These data can be used for studying the basic parameters,e.g.,metallicity,age,and initial and final masses of CCSN progenitors.It can also be used for studying the effects of different factors on the determination of parameters of CCSN progenitors.When the database is utilized for fitting the SEDs of binary-star CCSN progenitors,it is strongly suggested to determine the metallicity and orbital period in advance,but this is not necessary for single-star progenitors.展开更多
The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution hav...The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution have shown that the magnetic fields of WDs may significantly influence their accretion and nuclear burning processes.In this work we focus on the evolution of magnetized WD+He star binaries with detailed stellar evolution and binary population synthesis(BPS)calculations.In the case of magnetized WDs,the magnetic fields may disrupt the inner regions of the accretion disk,funnel the accretion flow onto the polar caps and even confine helium burning within the caps.We find that,for WDs with sufficiently strong magnetic fields,the parameter space of the potential SN Ia progenitor systems shrinks toward shorter orbital periods and lower donor masses compared with that in the non-magnetized WD case.The reason is that the magnetic confinement usually works with relatively high mass transfer rates,which can trigger strong wind mass loss from the WD,thus limiting the He-rich mass accumulation efficiency.The surviving companion stars are likely of low-mass at the moment of the SN explosions,which can be regarded as a possible explanation for the non-detection of surviving companions after the SNe or inside the SN remnants.However,the corresponding birthrate of Galactic SNe Ia in our high-magnetic models is estimated to be~(0.08–0.13)×10^(-3)yr^(-1)(~0.17–0.28×10^(-3)yr^(-1)for the non-magnetic models),significantly lower than the observed Galactic SN Ia birthrate.展开更多
The Binary star DataBase(BDB, http://bdb.inasan.ru) combines data from catalogs of binary and multiple stars of all observational types. There is a number of ways for variable stars to form or to be a part of binary o...The Binary star DataBase(BDB, http://bdb.inasan.ru) combines data from catalogs of binary and multiple stars of all observational types. There is a number of ways for variable stars to form or to be a part of binary or multiple systems. We describe how such stars are represented in the database.展开更多
The first BV bands photometric observations and the low-resolution spectrum of the shortest period Am type eclipsing binary TYC 6408-989-1 have been obtained.The stellar atmospheric parameters of the primary star were...The first BV bands photometric observations and the low-resolution spectrum of the shortest period Am type eclipsing binary TYC 6408-989-1 have been obtained.The stellar atmospheric parameters of the primary star were obtained through the spectral fitting as follows:Teff=6990±117 K,log g=4.25±0.26 cm s^(-2),[Fe/H]=-0.45±0.03 dex.The original spectra obtained by European Southern Observatory(ESO)were processed with an IRAF package by us.Based on the ESO blue-violet spectra,TYC 6408-989-1 was concluded as a marginal Am(Am:)star with a spectral type of kA3 hF1 mA5Ⅳ-Ⅴidentified through the MKCLASS program.The observed light curves were analyzed through the WilsonDevinney code.The final photometric solutions show that TYC 6408-989-1 is a marginal contact binary with a low mass ratio(q=0.27).The temperature of the secondary component derived through the light curve analysis is significantly higher than main sequence stars.In addition,TYC 6408-989-1 is a poor thermal contact binary.The temperature differences between the two components is about 1800 K.TYC6408-989-1 should be located in the oscillation stage predicted by the thermal relaxation oscillations theory(TRO)and will evolve into the shallow contact stage eventually.The very short period(less than one day),marginal Am peculiarity and quite large rotational velocity(v sin i■160 km s^(-1))make TYC 6408-989-1 become a challenge to the cut-off of rotation velocities and periods of Am stars.We have collected the well known eclipsing Am binaries with absolute parameters from the literature.展开更多
Three important physical processes occurring in contact binary systems are studied. The first one is the effect of spin, orbital rotation and tide on the structure of the components, which includes also the effect of ...Three important physical processes occurring in contact binary systems are studied. The first one is the effect of spin, orbital rotation and tide on the structure of the components, which includes also the effect of meridian circulation on the mixing of the chemical elements in the components. The second one is the mass and energy exchange between the components. To describe the energy exchange, a new approach is introduced based on the understanding that the exchange is due to the release of the potential, kinetic and thermal energy of the exchanged mass. The third is the loss of mass and angular momentum through the outer Lagrangian point. The rate of mass loss and the angular momentum carded away by the lost mass are discussed. To show the effects of these processes, we follow the evolution of a binary system consisting of a 12M⊙ and a 5M⊙ star with mass exchange between the components and mass loss via the outer Lagrangian point, both with and without considering the effects of rotation and tide. The result shows that the effect of rotation and tide advances the start of the semi-detached and the contact phases, and delays the end of the hydrogen-burning phase of the primary. Furthermore, it can change not only the occurrence of mass and angular momentum loss via the outer Lagrangian point, but also the contact or semi-contact status of the system. Thus, this effect can result in the special phenomenon of short-term variations occurring over a slow increase of the orbital period. The occurrence of mass and angular momentum loss via the outer Lagrangian point can affect the orbital period of the system significantly, but this process can be influenced, even suppressed out by the effect of rotation and tide. The mass and energy exchange occurs in the common envelope. The net result of the mass exchange process is a mass transfer from the primary to the secondary during the whole contact phase.展开更多
With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed ...With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs： hot Jupiter systems, standard systems and distant giant planet systems. The standard systems can be further categorized into three sub-types under different circumstances： solar-like systems, hot Super-Earth systems, and sub- giant planet systems. We also review the theory of planet detection and formation in binary systems as well as planets in star clusters.展开更多
基金supported by Yunnan Academician Workstation of Wang Jingxiu(202005AF150025)China Manned Space Project(NO.CMSCSST-2021-A08)+1 种基金Guanghe project(ghfund202302019167)the Natural Science Foundation of Yunnan Province(No.202201BC070003)。
文摘Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so far is limited,and the reasons for their formation are still unclear.This work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these features.Stellar population types and fundamental parameters of cluster samples are acquired using CMD fitting methods.Among them,the results of 11 OCs are reliable as the observed CMDs are well-reproduced.We propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO morphologies.The results also show that the impact of age spread is important,as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.
基金supported by National Key R&D Program of China No.2019YFA0405102,2019YFA0405500National Natural Science Foundation of China(NSFC,Grant Nos.11903027,11973001,11833006,U1731108,12090040and 12090044)+2 种基金Funding for the Sloan Digital Sky SurveyⅣhas been provided by the Alfred P.Sloan Foundationthe U.S.Department of Energy Office of Sciencesupport and resources from the Center for High-Performance Computing at the University of Utah。
文摘We present an updated catalog of 46,753 radial velocity(RV)standard stars selected from the APOGEE DR17.These stars cover the Northern and Southern Hemispheres almost evenly,with 62%being red giants and 38%being main sequence stars.These RV standard stars are stable on a baseline longer than 200 days(with 54%longer than one year and 10%longer than five years)with a median stability better than 215 m s~(-1).The average number of observations of those stars is 5 and each observation is required to have signal-to-noise ratio greater than50 and RV measurement error smaller than 500 m s~(-1).Based on the new APOGEE RV standard star catalog,we have checked the RV zero-points(RVZPs)for current large-scale stellar spectroscopic surveys including RAVE,LAMOST,GALAH and Gaia.By careful analysis,we estimate their mean RVZP to be+0.149 kms~(-1),+4.574 km s~(-1)(for LRS),-0.031 km s~(-1)and+0.014 kms~(-1),respectively,for the four surveys.In the RAVE,LAMOST(for MRS),GALAH and Gaia surveys,RVZP exhibits a systematic trend with stellar parameters(mainly[Fe/H],T_(eff),log g,G_(BP)-G_(RP)and G_(RVS)).The corrections to those small but clear RVZPs are of vital importance for these massive spectroscopic surveys in various studies that require extremely high RV accuracies.
基金supported by the National Science Foundation of China(NSFC 11673062)the China Manned Space Project(CMS-CSST-2021-A06)+7 种基金the Yunnan Revitalization Talent Support Program(Yun Ling Scholar Award)support from the Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2022ZB473)support from the NSFC(11773076 and 12073078)the National Key R&D Program of China(2017YFA0402703)science research grants from the China Manned Space Project(Nos.CMS-CSST-2021-A02,CMS-CSST-2021-A04 and CMS-CSST-2021-A07)support from the NSFC(11733006 and 12273052)support from the NSFC(12173079)support from the NSFC(U1831135)。
文摘GW170817 is the unique gravitational-wave(GW)event associated with the electromagnetic(EM)counterpart GRB 170817A.NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A.In this paper,we focus on the spatially resolved properties of NGC 4993.We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands.The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of a major galaxy merger.The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion.We derive the merging rate of the compact object per galaxy by a co-evolution scenario of a supermassive black hole and its host galaxy.If 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 Gyr.The results provide vital information for ongoing GW EM counterpart detections.The Hubble space telescope data analysis presented in this paper can be also applied to Chinese Space Station Telescope research in the future.
基金supported by the National Natural Science Foundation of China (Grant No. 11973026)the National Program on Key Research and Development Project (Grant No. 2021YFA0718500)。
文摘Mass distribution of black holes in low-mass X-ray binaries previously suggested the existence of a ~2–5 M⊙mass gap between the most massive neutron stars and the least massive black holes, while some recent evidence appears to support that this mass gap is being populated. Whether there is a mass gap or not can potentially shed light on the physics of supernova explosions that form neutron stars and black holes, although significant mass accretion of neutron stars including binary mergers may lead to the formation of mass-gap objects. In this review, I collect the compact objects that are probable black holes with masses being in the gap. Most of them are in binaries, their mass measurements are obviously subject to some uncertainties. Current observations are still unable to confidently infer an absence or presence of the mass gap. Ongoing and future surveys are expected to build the mass spectrum of black holes which can be used to constrain the process of their formation especially in binaries. I describe the theoretical predictions for the formation of black holes in various types of binaries, and present some prospects of searching for black holes via electromagnetic and gravitational wave observations.
基金supported by a grant from the Israel Science Foundation (769/20)。
文摘I review studies of core collapse supernovae(CCSNe) and similar transient events that attribute major roles to jets in powering most CCSNe and in shaping their ejecta. I start with reviewing the jittering jets explosion mechanism that I take to power most CCSN explosions. Neutrino heating does play a role in boosting the jets. I compare the morphologies of some CCSN remnants to planetary nebulae to conclude that jets and instabilities are behind the shaping of their ejecta. I then discuss CCSNe that are descendants of rapidly rotating collapsing cores that result in fixed-axis jets(with small jittering) that shape bipolar ejecta. A large fraction of the bipolar CCSNe are superluminous supernovae(SLSNe). I conclude that modeling of SLSN light curves and bumps in the light curves must include jets, even when considering energetic magnetars and/or ejecta interaction with the circumstellar matter(CSM). I connect the properties of bipolar CCSNe to common envelope jets supernovae(CEJSNe) where an old neutron star or a black hole spirals-in inside the envelope and then inside the core of a red supergiant. I discuss how jets can shape the pre-explosion CSM, as in Supernova 1987A, and can power pre-explosion outbursts(precursors)in binary system progenitors of CCSNe and CEJSNe. Binary interaction also facilitates the launching of postexplosion jets.
基金Supported by the research grants from the China Manned Space Project with No. CMS-CSST-2021-A08。
文摘We study the origin of the UV-excess in star clusters by performing N-body simulations of six clusters with N = 10 k and N = 100 k(single stars & binary systems) and metallicities of Z = 0.01, 0.001 and 0.0001, using PETAR. All models initially have a 50% primordial binary fraction. Using Galev NB we convert the simulated data into synthetic spectra and photometry for the China Space Station Telescope(CSST) and Hubble Space Telescope(HST). From the spectral energy distributions we identify three stellar populations that contribute to the UVexcess:(1) second asymptotic giant branch stars, which contribute to the UV flux at early times;(2) naked helium stars and(3) white dwarfs, which are long-term contributors to the FUV spectra. Binary stars consisting of a white dwarf and a main sequence star are cataclysmic variable(CV) candidates. The magnitude distribution of CV candidates is bimodal up to 2 Gyr. The bright CV population is particularly bright in FUV-NUV. The FUV-NUV color of our model clusters is 1–2 mag redder than the UV-excess globular clusters in M87 and in the Milky Way. This discrepancy may be induced by helium enrichment in observed clusters. Our simulations are based on simple stellar evolution;we do not include the effects of variations in helium and light elements or multiple stellar populations. A positive radial color gradient is present in CSST NUV-y for main sequence stars in all models with a color difference of 0.2–0.5 mag, up to 4 half-mass radii. The CSST NUV-g color correlates strongly with HST FUV-NUV for NUV-g > 1 mag, with the linear relation FUV-NUV =(1.09 ± 0.12) ×(NUV-g) +(-1.01 ± 0.22). This allows for conversion of future CSST NUV-g colors into HST FUV-NUV colors, which are sensitive to UV-excess features. We find that CSST will be able to detect UVexcess in Galactic/extragalactic star clusters with ages >200 Myr.
基金supported by the National Natural Science Foundation of China(Grant No.11863002)Sino-German Cooperation Project(Grant No.GZ 1284)Yunnan Academician Workstation of Wang Jingxiu(Grant No.202005AF150025)。
文摘This paper presents a database of the spectroscopic-and photometric-spectral energy distributions(spec-SEDs and phot-SEDs respectively)of the progenitors of core-collapse supernovae(CCSNe).Both binary-and single-star progenitors are included in the database.The database covers the initial metallicity(Z)range of 0.0001-0.03,mass range of 8-25 M⊙,binary mass ratio range of 0-1,and orbital period range of 0.1-10000 d.The low-resolution spec-SEDs and phot-SEDs of single-and binary-star CCSN progenitors are included in the database.These data can be used for studying the basic parameters,e.g.,metallicity,age,and initial and final masses of CCSN progenitors.It can also be used for studying the effects of different factors on the determination of parameters of CCSN progenitors.When the database is utilized for fitting the SEDs of binary-star CCSN progenitors,it is strongly suggested to determine the metallicity and orbital period in advance,but this is not necessary for single-star progenitors.
基金supported by the Natural Science Foundation of China(Grant Nos.11773015,12121003,12041301)Project U1838201 supported by NSFC and CAS。
文摘The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution have shown that the magnetic fields of WDs may significantly influence their accretion and nuclear burning processes.In this work we focus on the evolution of magnetized WD+He star binaries with detailed stellar evolution and binary population synthesis(BPS)calculations.In the case of magnetized WDs,the magnetic fields may disrupt the inner regions of the accretion disk,funnel the accretion flow onto the polar caps and even confine helium burning within the caps.We find that,for WDs with sufficiently strong magnetic fields,the parameter space of the potential SN Ia progenitor systems shrinks toward shorter orbital periods and lower donor masses compared with that in the non-magnetized WD case.The reason is that the magnetic confinement usually works with relatively high mass transfer rates,which can trigger strong wind mass loss from the WD,thus limiting the He-rich mass accumulation efficiency.The surviving companion stars are likely of low-mass at the moment of the SN explosions,which can be regarded as a possible explanation for the non-detection of surviving companions after the SNe or inside the SN remnants.However,the corresponding birthrate of Galactic SNe Ia in our high-magnetic models is estimated to be~(0.08–0.13)×10^(-3)yr^(-1)(~0.17–0.28×10^(-3)yr^(-1)for the non-magnetic models),significantly lower than the observed Galactic SN Ia birthrate.
基金supportedby the Russian Foundation of Basic Researches,projects 16–07–1162 and 18–02–00890Funding for the DPAC has been provided by nationalinstitutions, in particular the institutions participating inthe Gaia Multilateral Agreement
文摘The Binary star DataBase(BDB, http://bdb.inasan.ru) combines data from catalogs of binary and multiple stars of all observational types. There is a number of ways for variable stars to form or to be a part of binary or multiple systems. We describe how such stars are represented in the database.
基金partly supported by the National Natural Science Foundation of China(Nos.11922306 and U1831109)the Natural Science Foundation of Shandong Province(Nos.ZR2020QA048)+1 种基金the CAS Interdisciplinary Innovation Teampartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘The first BV bands photometric observations and the low-resolution spectrum of the shortest period Am type eclipsing binary TYC 6408-989-1 have been obtained.The stellar atmospheric parameters of the primary star were obtained through the spectral fitting as follows:Teff=6990±117 K,log g=4.25±0.26 cm s^(-2),[Fe/H]=-0.45±0.03 dex.The original spectra obtained by European Southern Observatory(ESO)were processed with an IRAF package by us.Based on the ESO blue-violet spectra,TYC 6408-989-1 was concluded as a marginal Am(Am:)star with a spectral type of kA3 hF1 mA5Ⅳ-Ⅴidentified through the MKCLASS program.The observed light curves were analyzed through the WilsonDevinney code.The final photometric solutions show that TYC 6408-989-1 is a marginal contact binary with a low mass ratio(q=0.27).The temperature of the secondary component derived through the light curve analysis is significantly higher than main sequence stars.In addition,TYC 6408-989-1 is a poor thermal contact binary.The temperature differences between the two components is about 1800 K.TYC6408-989-1 should be located in the oscillation stage predicted by the thermal relaxation oscillations theory(TRO)and will evolve into the shallow contact stage eventually.The very short period(less than one day),marginal Am peculiarity and quite large rotational velocity(v sin i■160 km s^(-1))make TYC 6408-989-1 become a challenge to the cut-off of rotation velocities and periods of Am stars.We have collected the well known eclipsing Am binaries with absolute parameters from the literature.
基金Supported by the National Natural Science Foundation of China.
文摘Three important physical processes occurring in contact binary systems are studied. The first one is the effect of spin, orbital rotation and tide on the structure of the components, which includes also the effect of meridian circulation on the mixing of the chemical elements in the components. The second one is the mass and energy exchange between the components. To describe the energy exchange, a new approach is introduced based on the understanding that the exchange is due to the release of the potential, kinetic and thermal energy of the exchanged mass. The third is the loss of mass and angular momentum through the outer Lagrangian point. The rate of mass loss and the angular momentum carded away by the lost mass are discussed. To show the effects of these processes, we follow the evolution of a binary system consisting of a 12M⊙ and a 5M⊙ star with mass exchange between the components and mass loss via the outer Lagrangian point, both with and without considering the effects of rotation and tide. The result shows that the effect of rotation and tide advances the start of the semi-detached and the contact phases, and delays the end of the hydrogen-burning phase of the primary. Furthermore, it can change not only the occurrence of mass and angular momentum loss via the outer Lagrangian point, but also the contact or semi-contact status of the system. Thus, this effect can result in the special phenomenon of short-term variations occurring over a slow increase of the orbital period. The occurrence of mass and angular momentum loss via the outer Lagrangian point can affect the orbital period of the system significantly, but this process can be influenced, even suppressed out by the effect of rotation and tide. The mass and energy exchange occurs in the common envelope. The net result of the mass exchange process is a mass transfer from the primary to the secondary during the whole contact phase.
基金supported by the National Natural Science Foundation of China (Nos. 10833001, 10925313, 11078001 and 11003010)Fundamental Research Funds for the Central Universities (No. 1112020102)the Research Fund for the Doctoral Program of Higher Education of China (Nos. 20090091110002 and 20090091120025)
文摘With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we sum- marize the major statistical results that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs： hot Jupiter systems, standard systems and distant giant planet systems. The standard systems can be further categorized into three sub-types under different circumstances： solar-like systems, hot Super-Earth systems, and sub- giant planet systems. We also review the theory of planet detection and formation in binary systems as well as planets in star clusters.
