PSR B1259–63 is a γ-ray emitting high mass X-ray binary system, in which the compact object is a millisecond pulsar.The system has an orbital period of 1236.7 d and shows peculiar γ-ray flares when the neutron star...PSR B1259–63 is a γ-ray emitting high mass X-ray binary system, in which the compact object is a millisecond pulsar.The system has an orbital period of 1236.7 d and shows peculiar γ-ray flares when the neutron star moves out of the stellar disk of the companion star.The γ-ray flare events were firstly discovered by using Fermi-LAT around the 2010 periastron passage, which was repeated for the 2014 and 2017 periastron passages.We analyze the Fermi-LAT data for all the three periastron passages and found that in each flare the energy spectrum can be represented well by a simple power law.The γ-ray light curves show that in 2010 and 2014 after each periastron there are two main flares,but in 2017 there are four flares including one precursor about 10 d after the periastron passage.The first main flares in 2010 and 2014 are located at around 35 d after the periastron passage, and the main flare in 2014 is delayed by roughly 1.7 d with respect to that in 2010.In the 2017 flare, the source shows a precursor about 10 d after the periastron passage, but the following two flares become weaker and lag behind those in 2010 by roughly 5 d.The strongest flares in 2017 occurred 58 d and 70 d after the periastron passage.These results challenge the previous models.展开更多
LS 5039 is a well-known γ-ray binary system which consists of an unknown compact object and a massive companion O star. It shows rather stable emissions at high energies over years and hence serves as an ideal labora...LS 5039 is a well-known γ-ray binary system which consists of an unknown compact object and a massive companion O star. It shows rather stable emissions at high energies over years and hence serves as an ideal laboratory to investigate the emission mechanism for such peculiar systems which emit prominent γ-rays. To this end, we take the orbital phase resolved energy spectrum as observed by Fermi-LAT over 10 years. We divide the orbit into four orbital phases, each with an orbital phase range of 0.25,centered at 0.00, 0.25, 0.50 and 0.75 respectively, where the phase 0.0 is the periastron and phase 0.5 is the apastron. The phases around 0.25 and 0.75 are symmetric and hence are supposed to have identical local acceleration environment. The spectral analysis shows that the Fermi-LAT spectra are largely different from these two symmetric orbital phases: the emission from orbital phase 0.25 turns out to be significantly stronger than that from 0.75. This result does not fit a scenario that γ-rays are Doppler boosted emission from bow shock tails if LS 5039 has a shock configuration similar to PSR B1259-63, and indicates that the inverse Compton scatterings between the shock accelerated plasma and the stellar particle environment is the underline procedure. We also find that the previous report for a disappearance of the orbital modulation at 3–20 GeV is due to the similar spectral turn-over energies of the different orbital phases. The spectral properties of periastron and apastron regions are addressed in the context of the measurements in phase regions around 0.25 and 0.75.展开更多
From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6...From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6 h)over 25 nights,yielding a total of about 767000 spectra,and the medium-resolution survey took 177 exposures(≈49.1 h)over 27 nights,collecting about 478000 spectra.More than 70%/50%of low-resolution/medium-resolution spectra have signal-to-noise ratio higher than 10.We determine stellar parameters(e.g.,Teff,log g,[Fe/H])and radial velocity(RV)with different methods,including LASP,DD-Payne and SLAM.In general,these parameter estimations from different methods show good agreement,and the stellar parameter values are consistent with those of APOGEE.We use the Gaia DR2 RV values to calculate a median RV zero point(RVZP)for each spectrograph exposure by exposure,and the RVZP-corrected RVs agree well with the APOGEE data.The stellar evolutionary and spectroscopic masses are estimated based on the stellar parameters,multi-band magnitudes,distances and extinction values.Finally,we construct a binary catalog including about 2700 candidates by analyzing their light curves,fitting the RV data,calculating the binarity parameters from medium-resolution spectra and cross-matching the spatially resolved binary catalog from Gaia EDR3.The LAMOST TD survey is expected to represent a breakthrough in various scientific topics,such as binary systems,stellar activity,stellar pulsation,etc.展开更多
The red giant branch(RGB)of globular clusters(GCs)is home to some exotic stars,which may provide clues on the formation of multiple stellar populations in GCs.It is well known that binary interactions are responsible ...The red giant branch(RGB)of globular clusters(GCs)is home to some exotic stars,which may provide clues on the formation of multiple stellar populations in GCs.It is well known that binary interactions are responsible for many exotic stars.Thus,it is important to understand what fraction of stars on the RGB of GCs is the result of binary interactions.In this paper,we performed a binary population synthesis study to track the number of post-binary-interaction(post-BI)stars that appear on the RGB,with particular emphasis on the evolved blue straggler stars(E-BSSs).Assuming an initial binary fraction of nearly 50%,we find that about half of the objects on the RGB(called giants)underwent the binary interactions,and that E-BSSs account for around 10%of the giants in our standard simulation.We also compare the properties of post-BI giants that evolved from different channels.We find that the initial orbital period and mass ratio distributions significantly affect the fraction of post-BI giants.Our results imply that the non-standard stars from binary interactions provide a non-negligible contribution to the RGB stars in GCs,which should be considered in future investigations of the origin of multiple stellar populations.展开更多
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
The pulsar timing residuals induced by gravitational waves from non- evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. W...The pulsar timing residuals induced by gravitational waves from non- evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The or- bits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities.展开更多
We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are...We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified). In addition, we recovered 11 old variables previously discovered by other authors. Preliminary parameters are given for some of these variables.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
There is accumulating evidence for mass ejection in low-mass X-ray binaries （LMXBs） driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pre...There is accumulating evidence for mass ejection in low-mass X-ray binaries （LMXBs） driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar, and the gas pressure at the inner Lagrange point or at the surrounding accretion disk. We calculate the critical spin period of the pulsar below which mass ejection is allowed. Combining with the evolution of the mass transfer rate, we present constraints on the orbital periods of the systems. We show that mass ejection could happen in both wide and compact LMXBs. It may be caused by transient accretion due to thermal instability in the accretion disks in the former, and irradiation-driven mass-transfer cycles in the latter.展开更多
A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W ...A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems,one EA type and two EB type eclipsing binaries （one of them could be a W UMa system）, and seven pulsating stars including three candidates of δ Scuti stars.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
Classical Newtonian f and g series for a Keplerian two-body problem are extended for the case of a post-Newtonian two-body problem with parameters β and γ. These two parameters are introduced to parameterize the pos...Classical Newtonian f and g series for a Keplerian two-body problem are extended for the case of a post-Newtonian two-body problem with parameters β and γ. These two parameters are introduced to parameterize the post-Newtonian approximation of alternative theories of gravity and they are both equal to1 in general relativity. Up to the order of 30, we obtain all of the coefficients of the series in their exact forms without any cutoff for significant figures. The f and g series for the post-Newtonian two-body problem are also compared with a Runge-Kutta order 7 integrator. Although the f and g series have no superiority in terms of accuracy or efficiency at the order of 7, the discrepancy in the performances of these two methods is not quite distinct. However, the f and g series have the advantage of flexibility for going to higher orders.Some examples of relativistic advance of periastron are given and the effect of gravitational radiation on the scheme of f and g series is evaluated.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
Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it ha...Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it has been erroneously adopted as a constant in most population synthesis calculations. We have system- atically calculated the values of A for stars of masses 1 - 60 M by use of an updated stellar evolution code, taking into account the contribution from both gravitational energy and internal energy to the binding energy of the envelope. We adopt the criterion for the core-envelope boundary advocated by Ivanova. A new kind of A with an enthalpy prescription is also investigated. We present fitting formulae for the calculated values of various kinds of A, which can be used in future population synthesis studies.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
基金support from the National Key R&D Program of China(Grant No.2016YFA0400800)the NSFC(Nos.U1838201,U1838202,11733009 and 11473027)+1 种基金XTP project(XDA 04060604)the Strategic Priority Research Programme‘The Emergence of Cosmological Structures’of the Chinese Academy of Sciences(Grant No.XDB09000000)
文摘PSR B1259–63 is a γ-ray emitting high mass X-ray binary system, in which the compact object is a millisecond pulsar.The system has an orbital period of 1236.7 d and shows peculiar γ-ray flares when the neutron star moves out of the stellar disk of the companion star.The γ-ray flare events were firstly discovered by using Fermi-LAT around the 2010 periastron passage, which was repeated for the 2014 and 2017 periastron passages.We analyze the Fermi-LAT data for all the three periastron passages and found that in each flare the energy spectrum can be represented well by a simple power law.The γ-ray light curves show that in 2010 and 2014 after each periastron there are two main flares,but in 2017 there are four flares including one precursor about 10 d after the periastron passage.The first main flares in 2010 and 2014 are located at around 35 d after the periastron passage, and the main flare in 2014 is delayed by roughly 1.7 d with respect to that in 2010.In the 2017 flare, the source shows a precursor about 10 d after the periastron passage, but the following two flares become weaker and lag behind those in 2010 by roughly 5 d.The strongest flares in 2017 occurred 58 d and 70 d after the periastron passage.These results challenge the previous models.
基金support from the National Key R&D Program of China (Grant No. 2016YFA0400800)the NSFC (Nos. U1838201, U1838202 and 11733009)XTP project (XDA 04060604)the Strategic Priority Research Programme ‘The Emergence of Cosmological Structures’ of the Chinese Academy of Sciences (Grant No. XDB09000000)
文摘LS 5039 is a well-known γ-ray binary system which consists of an unknown compact object and a massive companion O star. It shows rather stable emissions at high energies over years and hence serves as an ideal laboratory to investigate the emission mechanism for such peculiar systems which emit prominent γ-rays. To this end, we take the orbital phase resolved energy spectrum as observed by Fermi-LAT over 10 years. We divide the orbit into four orbital phases, each with an orbital phase range of 0.25,centered at 0.00, 0.25, 0.50 and 0.75 respectively, where the phase 0.0 is the periastron and phase 0.5 is the apastron. The phases around 0.25 and 0.75 are symmetric and hence are supposed to have identical local acceleration environment. The spectral analysis shows that the Fermi-LAT spectra are largely different from these two symmetric orbital phases: the emission from orbital phase 0.25 turns out to be significantly stronger than that from 0.75. This result does not fit a scenario that γ-rays are Doppler boosted emission from bow shock tails if LS 5039 has a shock configuration similar to PSR B1259-63, and indicates that the inverse Compton scatterings between the shock accelerated plasma and the stellar particle environment is the underline procedure. We also find that the previous report for a disappearance of the orbital modulation at 3–20 GeV is due to the similar spectral turn-over energies of the different orbital phases. The spectral properties of periastron and apastron regions are addressed in the context of the measurements in phase regions around 0.25 and 0.75.
文摘TESS(Transiting Exoplanet Survey Satellite)空间卫星提供的短曝光、高精度光度测量为寻找并区分变星与搜寻行星提供了良好的数据.利用变星源的光变曲线,使用周期频谱分析与光变折叠等一系列方法分析了TESS空间卫星21扇区19995颗拥有高质量光变数据的目标源,并对这些源进行了分类,共获得4624颗变星,其中食双星322颗、脉动变星470颗、行星凌星37颗.所得变星结果与VSX(The International Variable Star Index)变星表进行了交叉比较,共交叉匹配了625颗变星源,这些交叉源中共有131颗为食双星系统、31颗为脉动变星,并通过周期频谱分析获取了双星绕转以及脉动周期.另外在59颗变星中发现明显耀发现象,交叉源中有8颗变星为行星凌星并同样通过周期频谱分析获取了行星绕转周期,从而验证了TESS空间卫星数据对变星分析的可行性.通过利用TESS空间卫星21扇区获得的变星周期结果与VSX变星表中提供的变星周期对比,发现与VSX变星表中绝大部分变星的周期一致,有一部分结果与VSX变星表中的结果差别较大,对这些变星周期结果做了进一步修正,并给出了变星表未列出的变星周期结果.
基金the National Natural Science Foundation of China(Grant Nos.11988101,11933004 and 12003050)supported by the National Key Research and Development Program of China(Grant Nos.2019YFA0405000,2019YFA0405504 and 2016YFA0400804)+2 种基金the B-type Strategic Priority Program of the Chinese Academy of Sciences(CAS)under grant number XDB41000000the Youth Innovation Promotion Association of CAS(id.2019057 and 2020060,respectively)the European Research Council(ERC)under the European Union Horizon 2020 research and innovation programme(Cartograph Y GA.804752)。
文摘From Oct.2019 to Apr.2020,LAMOST performed a time-domain(TD)spectroscopic survey of four K2 plates with both low-and medium-resolution observations.The low-resolution spectroscopic survey acquired 282 exposures(≈46.6 h)over 25 nights,yielding a total of about 767000 spectra,and the medium-resolution survey took 177 exposures(≈49.1 h)over 27 nights,collecting about 478000 spectra.More than 70%/50%of low-resolution/medium-resolution spectra have signal-to-noise ratio higher than 10.We determine stellar parameters(e.g.,Teff,log g,[Fe/H])and radial velocity(RV)with different methods,including LASP,DD-Payne and SLAM.In general,these parameter estimations from different methods show good agreement,and the stellar parameter values are consistent with those of APOGEE.We use the Gaia DR2 RV values to calculate a median RV zero point(RVZP)for each spectrograph exposure by exposure,and the RVZP-corrected RVs agree well with the APOGEE data.The stellar evolutionary and spectroscopic masses are estimated based on the stellar parameters,multi-band magnitudes,distances and extinction values.Finally,we construct a binary catalog including about 2700 candidates by analyzing their light curves,fitting the RV data,calculating the binarity parameters from medium-resolution spectra and cross-matching the spatially resolved binary catalog from Gaia EDR3.The LAMOST TD survey is expected to represent a breakthrough in various scientific topics,such as binary systems,stellar activity,stellar pulsation,etc.
基金the National Natural Science Foundation of China(Grant Nos.12073070,11733008,11873085,11521303,12073071,11873016,11903075,12003027 and 11973081)the Natural Science Foundation of Yunnan Province(Nos.2017HC018,202001AT070058 and 202001AU070054)+8 种基金Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant Nos.2018076 and 2012048)the Chinese Academy of Sciences(CASKJZDEW-M06-01)for supportsupported by CAS‘Light of West China’Programsupported by the National Key Basic R&D Program of China(2019YFA0405500)the LAMOST Fellow project,funded by China Postdoctoral Science Foundation(Grant Nos.2019M653504 and 2020T130563)Yunnan province postdoctoral Directed culture Foundationthe Cultivation Project for LAMOST Scientific Payoff and Research Achievement of CAMS-CASthe science research grants from the China Manned Space Project(No.CMS-CSST-2021-A08)。
文摘The red giant branch(RGB)of globular clusters(GCs)is home to some exotic stars,which may provide clues on the formation of multiple stellar populations in GCs.It is well known that binary interactions are responsible for many exotic stars.Thus,it is important to understand what fraction of stars on the RGB of GCs is the result of binary interactions.In this paper,we performed a binary population synthesis study to track the number of post-binary-interaction(post-BI)stars that appear on the RGB,with particular emphasis on the evolved blue straggler stars(E-BSSs).Assuming an initial binary fraction of nearly 50%,we find that about half of the objects on the RGB(called giants)underwent the binary interactions,and that E-BSSs account for around 10%of the giants in our standard simulation.We also compare the properties of post-BI giants that evolved from different channels.We find that the initial orbital period and mass ratio distributions significantly affect the fraction of post-BI giants.Our results imply that the non-standard stars from binary interactions provide a non-negligible contribution to the RGB stars in GCs,which should be considered in future investigations of the origin of multiple stellar populations.
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 the National Natural Science Foundation of China
文摘The pulsar timing residuals induced by gravitational waves from non- evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The or- bits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities.
基金Supported by the National Natural Science Foundation of China.
文摘We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified). In addition, we recovered 11 old variables previously discovered by other authors. Preliminary parameters are given for some of these variables.
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supported by the Natural Science Foundation of China(Grant No.10873008)the Ministry of Science and the National Basic Research Program of China(973 ProgramGrant No.2009CB824800)
文摘There is accumulating evidence for mass ejection in low-mass X-ray binaries （LMXBs） driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar, and the gas pressure at the inner Lagrange point or at the surrounding accretion disk. We calculate the critical spin period of the pulsar below which mass ejection is allowed. Combining with the evolution of the mass transfer rate, we present constraints on the orbital periods of the systems. We show that mass ejection could happen in both wide and compact LMXBs. It may be caused by transient accretion due to thermal instability in the accretion disks in the former, and irradiation-driven mass-transfer cycles in the latter.
文摘A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems,one EA type and two EB type eclipsing binaries （one of them could be a W UMa system）, and seven pulsating stars including three candidates of δ Scuti stars.
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funded by the National Natural Science Foundation of China (Grant No.J1210039)the Fundamental Research Funds for the Central Universities (Grant No.20620140586)the Opening Project of Shanghai Key Laboratory of Space Navigation and Position Techniques (Grant No.14DZ2276100)
文摘Classical Newtonian f and g series for a Keplerian two-body problem are extended for the case of a post-Newtonian two-body problem with parameters β and γ. These two parameters are introduced to parameterize the post-Newtonian approximation of alternative theories of gravity and they are both equal to1 in general relativity. Up to the order of 30, we obtain all of the coefficients of the series in their exact forms without any cutoff for significant figures. The f and g series for the post-Newtonian two-body problem are also compared with a Runge-Kutta order 7 integrator. Although the f and g series have no superiority in terms of accuracy or efficiency at the order of 7, the discrepancy in the performances of these two methods is not quite distinct. However, the f and g series have the advantage of flexibility for going to higher orders.Some examples of relativistic advance of periastron are given and the effect of gravitational radiation on the scheme of f and g series is evaluated.
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funded by the National Natural Science Foundation of China(Grant Nos.11133001 and 11333004)the Strategic Priority Research Program of CAS(Grant No.XDB09000000)
文摘Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it has been erroneously adopted as a constant in most population synthesis calculations. We have system- atically calculated the values of A for stars of masses 1 - 60 M by use of an updated stellar evolution code, taking into account the contribution from both gravitational energy and internal energy to the binding energy of the envelope. We adopt the criterion for the core-envelope boundary advocated by Ivanova. A new kind of A with an enthalpy prescription is also investigated. We present fitting formulae for the calculated values of various kinds of A, which can be used in future population synthesis studies.
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.
