The subsurface convective zones (CZs) of massive stars significantly influence many of their key characteristics.Previous studies have paid little attention to the impact of rotation on the subsurface CZ,so we aim to ...The subsurface convective zones (CZs) of massive stars significantly influence many of their key characteristics.Previous studies have paid little attention to the impact of rotation on the subsurface CZ,so we aim to investigate the evolution of this zone in rapidly rotating massive stars.We use the Modules for Experiments in Stellar Astrophysics to simulate the subsurface CZs of massive stars during the main sequence phase.We establish stellar models with initial masses ranging from 5 M⊙to 120 M⊙,incorporating four metallicities (Z=0.02,0.006,0.002,and 0.0001) and three rotational velocities (ω/ωcrit=0,ω/ωcrit=0.50,andω/ωcrit=0.75).We find that rapid rotation leads to an expansion of the subsurface CZ,increases convective velocities,and promotes the development of this zone.Additionally,subsurface CZs can also emerge in stars with lower metallicities.Comparing our models with observations of massive stars in the Galaxy,the Large Magellanic Cloud,and the Small Magellanic Cloud,we find that rotating models better encompass the observed samples.Rotation significantly influences the evolution of the subsurface CZ in massive stars.By comparing with the observed microturbulence on the surfaces of OB stars,we propose that the subsurface CZs may be one of the sources of microturbulence.展开更多
In this paper,new light curve fitting and orbital period change analysis of two contact binaries NSVS 9023048 and NSVS 2461789 are presented.We found that both of them are totally eclipsing contact binaries.Our photom...In this paper,new light curve fitting and orbital period change analysis of two contact binaries NSVS 9023048 and NSVS 2461789 are presented.We found that both of them are totally eclipsing contact binaries.Our photometric solutions suggest that NSVS 9023048 is a deep contact binary(q=10.14,f=69.2%),however,NSVS 2461789is a shallow one(f=24.4%,q=3.08).The asymmetric light curves of NSVS 2461789 and NSVS 9023048 can be explained by the star-spot activity.At the same time,using the available eclipse times,we first studied the orbital period changes of these two targets.It is discovered that the period of NSVS 9023048 is decreasing at a rate of dP/dt=-1.17×10^(-6)day yr^(-1),which can be explained by mass transfer from the more massive star to the less massive one or angular momentum loss.In addition,the O-C diagrams of NSVS 9023048 and NSVS 2461789show possible cyclic oscillations with a period of 7.29 yr and 9.91 yr,respectively.The cyclic oscillations may be caused by the light-travel time effect due to the presence of a third component.The mass of the tertiary companion is determined to be M_(3)sin(i_(3))=9.05 Mefor NSVS 9023048 and M_(3)sin(i_(3))=0.11 Mefor NSVS 2461789.Based on our calculations,the third body of NSVS 9023048 may be a black hole candidate.Our study also reveals that NSVS 9023048 is stable now.展开更多
We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selec...We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10.By comparing their radial velocities with those predicted from the rotation curve of M31,as well as utilizing Gaia astrometric measurements to exclude foreground contaminations,199 supergiant members in M31,including 168“Rank1”and 31“Rank2,”have been successfully identified.This sample contains 62 blue supergiants(BSGs,all“Rank1”),134 yellow supergiants(YSGs,103“Rank1”and 31“Rank2”)and three red supergiants(RSGs,all“Rank1”).For M33,we identify 84 supergiant members(56“Rank1”and 28“Rank2”),which include 28 BSGs(all“Rank1”),53 YSGs(25“Rank1”and 28“Rank2”)and three RSGs(all“Rank1”).So far,this is one of the largest supergiant samples of M31/M33 with full optical wavelength coverage(3700<λ<9100Å).This sample is valuable for understanding star formation and stellar evolution under different environments.展开更多
Binary interactions lead to the formation of intriguing objects,such as compact binaries,supernovae,gamma ray bursts,X-ray binaries,pulsars,novae,cataclysmic variables,hot subdwarf stars,barium stars and blue straggle...Binary interactions lead to the formation of intriguing objects,such as compact binaries,supernovae,gamma ray bursts,X-ray binaries,pulsars,novae,cataclysmic variables,hot subdwarf stars,barium stars and blue stragglers.To study the evolution of binary populations and the consequent formation of these objects,many methods have been developed over the years,for which a robust approach named binary population synthesis(BPS)warrants special attention.This approach has seen widespread application in many areas of astrophysics,including but not limited to analyses of the stellar content of galaxies,research on galactic chemical evolution and studies concerning star formation and cosmic re-ionization.In this review,we discuss the role of BPS,its general picture and the various components that comprise it.We pay special attention to the stability criteria for mass transfer in binaries,as this stability largely determines the fate of binary systems.We conclude with our perspectives regarding the future of this field.展开更多
Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought ...Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought to the stellar surface by the global oscillating waves and becomes observable.For stellar evolutionary speed(i.e.,how long timescale does a star stay at a special evolution phase?),because of the insurmountable gap between the timescales of the evolutionary history of human civilization and a star,it can only be roughly tested by ensemble of stars in different evolutionary stages in most cases,and all the snapshots of these stars make up our global view of stellar evolution.The effect of stellar evolution on the structure and the corresponding global size of a pulsating star will lead to tiny period variations of its pulsation modes,which are the most valuable indicators of its evolutionary state and can be used to test the stellar evolution theory by a single star rather than ensemble of stars.Here,we report a High-AmplitudeδScuti star AE Ursae Majoris,which is located in the post main-sequence(MS)evolutionary stage and its observed linear period variation rate can be practically ascribed to its evolutionary effect.The result tests the stellar evolution theory from the pre-MS to post-MS with an unprecedented precision by a single star,and the framework can be extended to other type of pulsating stars to perform precise evolutionary asteroseismology,which aims to test the current stellar evolution theory in different evolutionary stages,discover the discrepancies between the theory and observations,and ultimately build a complete and precise stellar evolution theory to backtrack the history of each of these stars.展开更多
TypeⅡb supernovae(SNeⅡb)that have a thin layer of hydrogen left in their outer envelope have been believed to belong to core collapse supernovae.Mass transfer via Roche lobe overflow can significantly change the nuc...TypeⅡb supernovae(SNeⅡb)that have a thin layer of hydrogen left in their outer envelope have been believed to belong to core collapse supernovae.Mass transfer via Roche lobe overflow can significantly change the nucleosynthesis and surface chemical elements of the progenitors of SNeⅡb.We aim to explore what conditions a close binary can meet with the observational features of SNeⅡb.We find that an observed low mass SNⅡb cannot be produced by a low mass isolated star with M<20,M_(⊙)due to the existence of a thick hydrogen envelope regardless of rotation.Binaries dominate as progenitors in the mass interval(i.e.,M<20 M_(⊙))considered in this paper.The 16 M_(⊙),primary with a 14 M_(⊙) companion in a binary system with~10 days <P_(orb) <720 days can reproduce observational features of SNe Ⅱb(i.e.,T_(eff),log L/L_(⊙),M_(He),M_(H),etc.).With the decrease of the hydrogen-rich envelope mass,the radius of the progenitor shrinks.The associated types of SNⅡb progenitors from RSGs and YSGs to BSGs are closely related to the amount of hydrogen left in the envelopes.Rotation can bring the production of the CNO reaction to the stellar surface at an early phase,which would explain the nitrogen-rich circumstellar material of SN 1993 J and can also explain the large He/H ratio of supernova ejecta.Rotation can increase the corresponding region of the orbital period which can produce an SNⅡb.展开更多
Motivated by the determination of black hole masses with gravitational-wave observations,we calculate the evolution of massive stars through presupernova stages and obtain the mass distribution of black holes.In the f...Motivated by the determination of black hole masses with gravitational-wave observations,we calculate the evolution of massive stars through presupernova stages and obtain the mass distribution of black holes.In the first part,we calculate the evolution of He stars with masses of 30-120 M_(⊙).We study in detail how convective carbon shell burning controls pair-instability pulsations before and during oxygen burning and determine their final fates.In the second part,we calculate the evolution of H-rich stars with initial masses of 13-80 M_(⊙) until Fe core collapse and obtain the possible black hole mass range by applying the criterion of the compactness parameters.From these models,we predict the mass distribution of black holes for stars that undergo Fe core collapse and pair-instability pulsation.The predicted masses for black holes range from 4.2 to 46 M_(⊙),which are consistent with the gravitational-wave observations.展开更多
In this study,we determined the physical parameters of W UMa type contact binaries and their stability of mass transfer with different stellar mass ranges over a broad space by applying the basic dynamical evolution e...In this study,we determined the physical parameters of W UMa type contact binaries and their stability of mass transfer with different stellar mass ranges over a broad space by applying the basic dynamical evolution equations of the W UMa type contact binaries using accretor and donor masses between 0.079 and 2.79 M_(⊙).In these systems,we have studied the three subclasses of W UMa systems of A-,B-and W-type contact binaries using the initial and final mass ranges and we investigated different stellar and orbital parameters for the subclasses of W UMa systems.We examined the stability of the W UMa type contact binaries using the orbital parameters such as critical mass ratio,Roche lobe radius of the donor star and mass ratio of these systems.Thus,we computed the observed and calculated physical parameters of A-,B-and W-type W UMa systems.Moreover,we determined the combined and color temperatures to classify the three subclasses of the systems.Also,we presented the result of the internal stellar structure and evolution of W UMa type contact binaries by using the polytropic model.展开更多
We present the first photometric and orbital period investigations for a neglected totally eclipsing contact binary IP Lyn.The photometric solutions derived from both ground-based and several surveys'observations ...We present the first photometric and orbital period investigations for a neglected totally eclipsing contact binary IP Lyn.The photometric solutions derived from both ground-based and several surveys'observations suggest that it is a shallow contact binary with an extremely low mass ratio of 0.055.The weak asymmetry observed in our multiple band light curves can be interpreted as a result of an active cool spot on the primary.The absolute physical parameters were determined with the Gaia-distance-based method and checked by an empirical relation.Combining the eclipse timings collected from the literature and those derived from our and variable surveys'observations,we find that IP Lyn has been undergoing a secular orbital period increase for the past two decades,implying a mass transfer from the less massive secondary to the primary.By comparing the current parameters with the critical instability ones,we infer that IP Lyn is currently stable in spite of its relatively low mass ratio and orbital angular momentum.Finally,from a catalog of 117 extremely low mass ratio contact binaries,we find that their orbital angular momenta are significantly lower than those of the contact binaries with a relatively high mass ratio,suggesting they should be at the late evolutionary stage of a contact binary.展开更多
The binary systems consisting of a Be star and a white dwarf(Be WDs) are very interesting.They can originate from the binaries composed of a Be star and a subdwarf O or B star(Besd OBs),and they can merge into red gia...The binary systems consisting of a Be star and a white dwarf(Be WDs) are very interesting.They can originate from the binaries composed of a Be star and a subdwarf O or B star(Besd OBs),and they can merge into red giants via luminous red nova or can evolve into double WD potentially detected by the LISA mission.Using the method of population synthesis,we investigate the formation and the destiny of Be WDs,and discuss the effects of the metallicity(Z) and the common envelope evolution parameters.We find that Besd OBs are significant progenitors of Be WDs.About 30%(Z = 0.0001)-50%(Z = 0.02) of Be WDs come from Besd OBs.About 60%(Z = 0.0001)-70%(Z = 0.02) of Be WDs turn into red giants via a merger between a WD and a non-degenerated star.About 30%(Z = 0.0001)-40%(Z = 0.02) of Be WDs evolve into double WDs which are potential gravitational waves of the LISA mission at a frequency band between about 3 × 10^(-3)and 3 × 10^(-2)Hz.The common envelope evolution parameter introduces an uncertainty with a factor of about 1.3 on Be WD populations in our simulations.展开更多
W UMi is a near contact,semi-detached,double-lined eclipsing binary star with an orbital period of 1.7 d.Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysica...W UMi is a near contact,semi-detached,double-lined eclipsing binary star with an orbital period of 1.7 d.Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysical parameters of the binary and its component stars.We determined mass and radius to be M1=3.22±0.08 M⊙,R1=3.63±0.04 R⊙for the primary star and M2=1.44±0.05 M⊙,R2=3.09±0.03 R⊙for the secondary star.Based on analysis of mid-eclipse times,variation in the orbital period is represented by a cyclic term and a downward parabola.Mass loss from the system is suggested for a secular decrease(-0.02 s yr-1)in the period.Both the mechanisms of a hypothetical tertiary star orbiting around W UMi and the surface magnetic activity of the less massive cooler companion were used to interpret periodic changes.Observational parameters were found to be consistent with binary stellar evolution models produced in the non-conservative approach of MESA at a higher metallicity than the Sun and an age of about 400 Myr for the system.Evidence that the system is rich in metal was obtained from spectral and kinematic analysis as well as evolution models.W UMi,a high mass ratio system compared to classical semi-detached binaries,is an important example since it is estimated from binary evolutionary models that the system may reach its contact phase in a short time interval.展开更多
基金the National Natural Science Foundation of China under grant Nos.U2031204,12163005,12373038,12288102,and 12263006the science research grant from the China Manned Space Project with No.CMSCSST-2021-A10+1 种基金the Natural Science Foundation of Xinjiang Nos.2022D01D85 and 2022TSYCLJ0006the Major Science and Technology Program of Xinjiang Uygur Autonomous Region under grant No.2022A03013-3.
文摘The subsurface convective zones (CZs) of massive stars significantly influence many of their key characteristics.Previous studies have paid little attention to the impact of rotation on the subsurface CZ,so we aim to investigate the evolution of this zone in rapidly rotating massive stars.We use the Modules for Experiments in Stellar Astrophysics to simulate the subsurface CZs of massive stars during the main sequence phase.We establish stellar models with initial masses ranging from 5 M⊙to 120 M⊙,incorporating four metallicities (Z=0.02,0.006,0.002,and 0.0001) and three rotational velocities (ω/ωcrit=0,ω/ωcrit=0.50,andω/ωcrit=0.75).We find that rapid rotation leads to an expansion of the subsurface CZ,increases convective velocities,and promotes the development of this zone.Additionally,subsurface CZs can also emerge in stars with lower metallicities.Comparing our models with observations of massive stars in the Galaxy,the Large Magellanic Cloud,and the Small Magellanic Cloud,we find that rotating models better encompass the observed samples.Rotation significantly influences the evolution of the subsurface CZ in massive stars.By comparing with the observed microturbulence on the surfaces of OB stars,we propose that the subsurface CZs may be one of the sources of microturbulence.
基金supported by the National Natural Science Foundation of China(Nos.11988101,U1931101,42364001 and 11933008)the Foundation of Education Bureau of Guizhou Province,China(No.KY(2020)003)+1 种基金the Guizhou Provincial Science and Technology Foundation(No.ZK[2022]322)the Guizhou Normal University 2019Special project of training new academics。
文摘In this paper,new light curve fitting and orbital period change analysis of two contact binaries NSVS 9023048 and NSVS 2461789 are presented.We found that both of them are totally eclipsing contact binaries.Our photometric solutions suggest that NSVS 9023048 is a deep contact binary(q=10.14,f=69.2%),however,NSVS 2461789is a shallow one(f=24.4%,q=3.08).The asymmetric light curves of NSVS 2461789 and NSVS 9023048 can be explained by the star-spot activity.At the same time,using the available eclipse times,we first studied the orbital period changes of these two targets.It is discovered that the period of NSVS 9023048 is decreasing at a rate of dP/dt=-1.17×10^(-6)day yr^(-1),which can be explained by mass transfer from the more massive star to the less massive one or angular momentum loss.In addition,the O-C diagrams of NSVS 9023048 and NSVS 2461789show possible cyclic oscillations with a period of 7.29 yr and 9.91 yr,respectively.The cyclic oscillations may be caused by the light-travel time effect due to the presence of a third component.The mass of the tertiary companion is determined to be M_(3)sin(i_(3))=9.05 Mefor NSVS 9023048 and M_(3)sin(i_(3))=0.11 Mefor NSVS 2461789.Based on our calculations,the third body of NSVS 9023048 may be a black hole candidate.Our study also reveals that NSVS 9023048 is stable now.
基金funded by the National Natural Science Foundation of China(NSFC,grant Nos.12090040,12090044,12133001,and 12422303)Beijing Natural Science Foundation(no.1242016)+2 种基金the science research grants from the China Manned Space Projectsupported by the Talents Program(24CE-YS-08)the Popular Science Project(24CD012)of the Beijing Academy of Science and Technology.
文摘We present systematic identifications of supergiants in M31/M33 based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)spectroscopic survey.Radial velocities of nearly 5000 photometrically selected M31/M33 supergiant candidates have been properly derived from the qualified spectra released in LAMOST DR10.By comparing their radial velocities with those predicted from the rotation curve of M31,as well as utilizing Gaia astrometric measurements to exclude foreground contaminations,199 supergiant members in M31,including 168“Rank1”and 31“Rank2,”have been successfully identified.This sample contains 62 blue supergiants(BSGs,all“Rank1”),134 yellow supergiants(YSGs,103“Rank1”and 31“Rank2”)and three red supergiants(RSGs,all“Rank1”).For M33,we identify 84 supergiant members(56“Rank1”and 28“Rank2”),which include 28 BSGs(all“Rank1”),53 YSGs(25“Rank1”and 28“Rank2”)and three RSGs(all“Rank1”).So far,this is one of the largest supergiant samples of M31/M33 with full optical wavelength coverage(3700<λ<9100Å).This sample is valuable for understanding star formation and stellar evolution under different environments.
基金supported by the National Natural Science Foundation of China(Nos 11521303,11733008,11673058 and 11703081)the Key Research Programme of Frontier Sciences of the CAS(No.ZDBS-LY-7005)。
文摘Binary interactions lead to the formation of intriguing objects,such as compact binaries,supernovae,gamma ray bursts,X-ray binaries,pulsars,novae,cataclysmic variables,hot subdwarf stars,barium stars and blue stragglers.To study the evolution of binary populations and the consequent formation of these objects,many methods have been developed over the years,for which a robust approach named binary population synthesis(BPS)warrants special attention.This approach has seen widespread application in many areas of astrophysics,including but not limited to analyses of the stellar content of galaxies,research on galactic chemical evolution and studies concerning star formation and cosmic re-ionization.In this review,we discuss the role of BPS,its general picture and the various components that comprise it.We pay special attention to the stability criteria for mass transfer in binaries,as this stability largely determines the fate of binary systems.We conclude with our perspectives regarding the future of this field.
基金support from the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)(No.2020L0528)the Applied Basic Research Programs of Natural Science Foundation of Shanxi Province(No.202103021223320)+1 种基金support from the National Natural Science Foundation of China(NSFC)(Nos.12005124 and 12147215)support from the NSFC(Nos.11833002,12090040,and 12090042)。
文摘Stellar structure and evolution theory is one of the bases in modern astronomy.Stellar inner structures and their evolutionary states can be precisely tested by asteroseismology,since the inner information is brought to the stellar surface by the global oscillating waves and becomes observable.For stellar evolutionary speed(i.e.,how long timescale does a star stay at a special evolution phase?),because of the insurmountable gap between the timescales of the evolutionary history of human civilization and a star,it can only be roughly tested by ensemble of stars in different evolutionary stages in most cases,and all the snapshots of these stars make up our global view of stellar evolution.The effect of stellar evolution on the structure and the corresponding global size of a pulsating star will lead to tiny period variations of its pulsation modes,which are the most valuable indicators of its evolutionary state and can be used to test the stellar evolution theory by a single star rather than ensemble of stars.Here,we report a High-AmplitudeδScuti star AE Ursae Majoris,which is located in the post main-sequence(MS)evolutionary stage and its observed linear period variation rate can be practically ascribed to its evolutionary effect.The result tests the stellar evolution theory from the pre-MS to post-MS with an unprecedented precision by a single star,and the framework can be extended to other type of pulsating stars to perform precise evolutionary asteroseismology,which aims to test the current stellar evolution theory in different evolutionary stages,discover the discrepancies between the theory and observations,and ultimately build a complete and precise stellar evolution theory to backtrack the history of each of these stars.
基金supported by the National Natural Science Foundation of China(Grant Nos.11863003 and 12173010)Science and technology plan projects of Guizhou province(Grant No.[2018]5781)。
文摘TypeⅡb supernovae(SNeⅡb)that have a thin layer of hydrogen left in their outer envelope have been believed to belong to core collapse supernovae.Mass transfer via Roche lobe overflow can significantly change the nucleosynthesis and surface chemical elements of the progenitors of SNeⅡb.We aim to explore what conditions a close binary can meet with the observational features of SNeⅡb.We find that an observed low mass SNⅡb cannot be produced by a low mass isolated star with M<20,M_(⊙)due to the existence of a thick hydrogen envelope regardless of rotation.Binaries dominate as progenitors in the mass interval(i.e.,M<20 M_(⊙))considered in this paper.The 16 M_(⊙),primary with a 14 M_(⊙) companion in a binary system with~10 days <P_(orb) <720 days can reproduce observational features of SNe Ⅱb(i.e.,T_(eff),log L/L_(⊙),M_(He),M_(H),etc.).With the decrease of the hydrogen-rich envelope mass,the radius of the progenitor shrinks.The associated types of SNⅡb progenitors from RSGs and YSGs to BSGs are closely related to the amount of hydrogen left in the envelopes.Rotation can bring the production of the CNO reaction to the stellar surface at an early phase,which would explain the nitrogen-rich circumstellar material of SN 1993 J and can also explain the large He/H ratio of supernova ejecta.Rotation can increase the corresponding region of the orbital period which can produce an SNⅡb.
基金supported by the National Natural Science Foundation of China under Grant Nos.11988101 and 11890694the National Key R&D Program of China No.2019YFA0405502+1 种基金supported by the World Premier International Research Center Initiative(WPI),MEXT,Japanthe Japan Society for the Promotion of Science(JSPS)KAKENHI grants JP17K05382,JP20K04024 and JP21H04499。
文摘Motivated by the determination of black hole masses with gravitational-wave observations,we calculate the evolution of massive stars through presupernova stages and obtain the mass distribution of black holes.In the first part,we calculate the evolution of He stars with masses of 30-120 M_(⊙).We study in detail how convective carbon shell burning controls pair-instability pulsations before and during oxygen burning and determine their final fates.In the second part,we calculate the evolution of H-rich stars with initial masses of 13-80 M_(⊙) until Fe core collapse and obtain the possible black hole mass range by applying the criterion of the compactness parameters.From these models,we predict the mass distribution of black holes for stars that undergo Fe core collapse and pair-instability pulsation.The predicted masses for black holes range from 4.2 to 46 M_(⊙),which are consistent with the gravitational-wave observations.
基金the Space Science and Geospatial Institute (SSGI) -Entoto Observatory and Research Center (EORC)Astronomy and Astrophysics Department for supporting this research。
文摘In this study,we determined the physical parameters of W UMa type contact binaries and their stability of mass transfer with different stellar mass ranges over a broad space by applying the basic dynamical evolution equations of the W UMa type contact binaries using accretor and donor masses between 0.079 and 2.79 M_(⊙).In these systems,we have studied the three subclasses of W UMa systems of A-,B-and W-type contact binaries using the initial and final mass ranges and we investigated different stellar and orbital parameters for the subclasses of W UMa systems.We examined the stability of the W UMa type contact binaries using the orbital parameters such as critical mass ratio,Roche lobe radius of the donor star and mass ratio of these systems.Thus,we computed the observed and calculated physical parameters of A-,B-and W-type W UMa systems.Moreover,we determined the combined and color temperatures to classify the three subclasses of the systems.Also,we presented the result of the internal stellar structure and evolution of W UMa type contact binaries by using the polytropic model.
基金supported by the Joint Research Funds in Astronomy under a cooperative agreement between the National Natural Science Foundation of China(NSFC)and the Chinese Academy of Sciences(Nos.U1931115 and U2031114)Scientific Research Fund of Hunan Provincial Education Department grant No.22A0099+1 种基金the support of the staff of the Xinglong 85 cm telescopepartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences。
文摘We present the first photometric and orbital period investigations for a neglected totally eclipsing contact binary IP Lyn.The photometric solutions derived from both ground-based and several surveys'observations suggest that it is a shallow contact binary with an extremely low mass ratio of 0.055.The weak asymmetry observed in our multiple band light curves can be interpreted as a result of an active cool spot on the primary.The absolute physical parameters were determined with the Gaia-distance-based method and checked by an empirical relation.Combining the eclipse timings collected from the literature and those derived from our and variable surveys'observations,we find that IP Lyn has been undergoing a secular orbital period increase for the past two decades,implying a mass transfer from the less massive secondary to the primary.By comparing the current parameters with the critical instability ones,we infer that IP Lyn is currently stable in spite of its relatively low mass ratio and orbital angular momentum.Finally,from a catalog of 117 extremely low mass ratio contact binaries,we find that their orbital angular momenta are significantly lower than those of the contact binaries with a relatively high mass ratio,suggesting they should be at the late evolutionary stage of a contact binary.
基金the generous support of the Natural Science Foundation of Xinjiang No.2021D01C075the National Natural Science Foundation of China+1 种基金project Nos.12163005,U2031204 and 11863005the science research grants from the China Manned Space Project with No.CMSCSST-2021-A10。
文摘The binary systems consisting of a Be star and a white dwarf(Be WDs) are very interesting.They can originate from the binaries composed of a Be star and a subdwarf O or B star(Besd OBs),and they can merge into red giants via luminous red nova or can evolve into double WD potentially detected by the LISA mission.Using the method of population synthesis,we investigate the formation and the destiny of Be WDs,and discuss the effects of the metallicity(Z) and the common envelope evolution parameters.We find that Besd OBs are significant progenitors of Be WDs.About 30%(Z = 0.0001)-50%(Z = 0.02) of Be WDs come from Besd OBs.About 60%(Z = 0.0001)-70%(Z = 0.02) of Be WDs turn into red giants via a merger between a WD and a non-degenerated star.About 30%(Z = 0.0001)-40%(Z = 0.02) of Be WDs evolve into double WDs which are potential gravitational waves of the LISA mission at a frequency band between about 3 × 10^(-3)and 3 × 10^(-2)Hz.The common envelope evolution parameter introduces an uncertainty with a factor of about 1.3 on Be WD populations in our simulations.
基金Canakkale Onsekiz Mart University,the Scientific Research Coordination Unit,Project number:FBA-2018–2549supported by TUBITAK(Scientific and Technological Research Council of Turkey)under Grant No.111T224Funding for the DPAC has been provided by national institutions,in particular the institutions participating in the Gaia Multilateral Agreement。
文摘W UMi is a near contact,semi-detached,double-lined eclipsing binary star with an orbital period of 1.7 d.Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysical parameters of the binary and its component stars.We determined mass and radius to be M1=3.22±0.08 M⊙,R1=3.63±0.04 R⊙for the primary star and M2=1.44±0.05 M⊙,R2=3.09±0.03 R⊙for the secondary star.Based on analysis of mid-eclipse times,variation in the orbital period is represented by a cyclic term and a downward parabola.Mass loss from the system is suggested for a secular decrease(-0.02 s yr-1)in the period.Both the mechanisms of a hypothetical tertiary star orbiting around W UMi and the surface magnetic activity of the less massive cooler companion were used to interpret periodic changes.Observational parameters were found to be consistent with binary stellar evolution models produced in the non-conservative approach of MESA at a higher metallicity than the Sun and an age of about 400 Myr for the system.Evidence that the system is rich in metal was obtained from spectral and kinematic analysis as well as evolution models.W UMi,a high mass ratio system compared to classical semi-detached binaries,is an important example since it is estimated from binary evolutionary models that the system may reach its contact phase in a short time interval.
