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
In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star g...In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.展开更多
AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the dise...AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.展开更多
δScuti(δSct)stars are potential distance tracers for studying the Milky Way structure.We conduct a comprehensive analysis of the period-luminosity(PL)and period-luminosity-metallicity(PLZ)relations forδSct stars,in...δScuti(δSct)stars are potential distance tracers for studying the Milky Way structure.We conduct a comprehensive analysis of the period-luminosity(PL)and period-luminosity-metallicity(PLZ)relations forδSct stars,integrating data from the Zwicky Transient Facility,the Transiting Exoplanet Survey Satellite,Large Sky Area Multi-Object Fiber Spectroscopic Telescope,Apache Point Observatory Galactic Evolution Experiment,and Gaia.To mitigate the impact of the Gaia parallax zero point offset,we applied a correction method,determining the optimal zero point value to be zp(?)=35±2μas.Using the three best bands,by varying the parallax error threshold,we found that the total error of the PLR zero point was minimized to 0.9%at a parallax error threshold of 6%.With this threshold,we derived the PL and PLZ relations for nine bands(from optical to mid-infrared)and five Wesenheit bands.Through our analysis,we conclude that the influence of metallicity on the PLR ofδSct stars is not significant,and the differences across various bands are minimal.展开更多
We presented the first photometric light curve solutions of four W Ursae Majoris-type contact binary systems.This investigation utilized photometric data from the Transiting Exoplanet Survey Satellite and Gaia Data Re...We presented the first photometric light curve solutions of four W Ursae Majoris-type contact binary systems.This investigation utilized photometric data from the Transiting Exoplanet Survey Satellite and Gaia Data Release 3(DR3).We used the PHysics Of Eclipsing BinariEs Python code and the Markov Chain Monte Carlo method for these light curve solutions.Only TIC 249064185 among the target systems needed a cold starspot to be included in the analysis.Based on the estimated mass ratios for these total eclipse systems,three of them are categorized as low mass ratio contact binary stars.The absolute parameters of the systems were estimated using the Gaia DR3 parallax method and the orbital period and semimajor axis(P-a)empirical relationship.We ascertained that the TIC 318015356 and TIC 55522736 systems are A-subtypes,while TIC 249064185 and TIC 397984843 are W-subtypes,depending on each component’s effective temperature and mass.We estimated the initial masses of the stars,the mass lost by the binary system,and the systems’ages.We displayed star positions in the mass-radius,mass-luminosity,and total mass-orbital angular momentum diagrams.In addition,our findings indicate a good agreement with the mass-temperature empirical parameter relationship for the primary stars.展开更多
Sulfur-bearing molecules are frequently detected in star-forming regions.The abundance ratio of SO to SO_(2)(hereafter,SO/SO_(2) ratio)has been proposed as a potential evolutionary tracer of star formation because ten...Sulfur-bearing molecules are frequently detected in star-forming regions.The abundance ratio of SO to SO_(2)(hereafter,SO/SO_(2) ratio)has been proposed as a potential evolutionary tracer of star formation because tentative correlations have been found between SO/SO_(2) ratio and evolutionary stages.Nonetheless,the lack of highresolution observations and extensive statistical analyses of large samples raises questions regarding its efficacy as an evolutionary tracer.In this study,we analyze 31 protostellar cores with both SO and SO_(2) detection to investigate the relationship between the SO/SO_(2) ratio and two evolutionary parameters of chemical richness factor and gas temperatures.The correlations between SO/SO_(2) ratio and evolutionary parameters have been found,but these correlations are mainly contributed by low-mass cores rather than high-mass cores.Our findings suggest that the SO/SO_(2) ratio serves as a reliable evolutionary tracer for low-mass dense cores.In high-mass cores,the relationship between the SO/SO_(2) ratio and evolutionary stage remains ambiguous.This likely arises from both vigorous stellar feedback effects and the potential absence of distinct evolutionary stages analogous to those in low-mass cores.Consequently,higher-resolution observations with expanded statistical samples are required to assess the viability of SO/SO_(2) ratio as an evolutionary tracer for high-mass cores.展开更多
The availability of large data sets containing stellar parameters,distances,and extinctions for stars in the Milky Way,particularly within the Galactic disk,is essential for advancing our understanding of the Galaxy’...The availability of large data sets containing stellar parameters,distances,and extinctions for stars in the Milky Way,particularly within the Galactic disk,is essential for advancing our understanding of the Galaxy’s stellar populations,structure,kinematics,and chemical evolution.In this study,we present a catalog of stellar parameters,including effective temperature (T_(eff)),metallicity ([Fe/H]),absolute magnitudes (M_(G)),distances (d),and reddening values (E(G_(BP)-G_(RP))),for a sample of 141 million stars from the SkyMapper Southern Survey.These parameters are derived using the SPar algorithm,which employs a fitting procedure to match multi-band photometric observations and estimate the stellar properties (T_(eff),[Fe/H],M_(G),d,and E(G_(BP)-G_(RP))) on an individual star basis,following the methodology outlined in our previous work.This study successfully determines stellar parameters and extinction values simultaneously for stars located in high and low Galactic latitudes.The resulting stellar parameters and extinction values are in good agreement with results from other studies,demonstrating the robustness of our method.We derive a temperature dispersion of 195 K and a metallicity dispersion of 0.31 dex when comparing our results with spectroscopic data.The catalog produced in this work provides a valuable resource for future research on the Galactic metallicity distribution function,the structure of the Galaxy,threedimensional extinction mapping,and other related astrophysical topics.展开更多
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
Hot subdwarf stars are important celestial objects in the study of stellar physics,but the population remains limited.The LAMOST DR12-V1,released in 2025 March,is currently the world’s largest spectroscopic database,...Hot subdwarf stars are important celestial objects in the study of stellar physics,but the population remains limited.The LAMOST DR12-V1,released in 2025 March,is currently the world’s largest spectroscopic database,holding great potential for the search of hot subdwarf stars.In this study,we propose a two-stage deep learning model called the hot subdwarf network(HsdNet),which integrates multiple advanced techniques,comprising a binary classification model in stage one and a five-class classification model in stage two.HsdNet not only achieves high precision with 94.33%and 94.00%in the binary and the five-class classification stages,respectively,but also quantifies the predicted uncertainty,enhancing the interpretability of the classification results through visualizing the model’s key focus regions.We applied HsdNet to the 601,217 spectra from the LAMOST DR12-V1 database,conducting a two-stage search for hot subdwarf candidates.In stage one,we initially identified candidates using the binary classification model.In stage two,the five-class classification model was used to further refine these candidates.Finally,we confirmed 1008 newly identified hot subdwarf stars.The distribution of their atmospheric parameters is consistent with that of known hot subdwarf stars.These efforts are expected to significantly advance the research on hot subdwarf stars.展开更多
We propose that the core mass function(CMF)can be driven by filament fragmentation.To model a star-forming system of filaments and fibers,we develop a fractal and turbulent tree with a fractal dimension of 2 and a Lar...We propose that the core mass function(CMF)can be driven by filament fragmentation.To model a star-forming system of filaments and fibers,we develop a fractal and turbulent tree with a fractal dimension of 2 and a Larson's law exponent(β)of 0.5.The fragmentation driven by convergent flows along the splines of the fractal tree yields a Kroupa-IMF-like CMF that can be divided into three power-law segments with exponentsα=-0.5,-1.5,and-2,respectively.The turnover masses of the derived CMF are approximately four times those of the Kroupa IMF,corresponding to a star formation efficiency of 0.25.Adoptingβ=1/3,which leads to fractional Brownian motion along the filament,may explain a steeper CMF at the high-mass end,withα=-3.33 close to that of the Salpeter IMF.We suggest that the fibers of the tree are basic building blocks of star formation,with similar properties across different clouds,establishing a common density threshold for star formation and leading to a universal CMF.展开更多
在分子云中,新生恒星之间的关系复杂且多样,这些关系对恒星的形成和演化过程具有重要影响。本文以Sgr C Cores为研究对象,利用DS9软件制作RGB三色图,并测量了云核质量、外流长度与年龄等基本物理性质。通过数据分析,探讨了云核质量与外...在分子云中,新生恒星之间的关系复杂且多样,这些关系对恒星的形成和演化过程具有重要影响。本文以Sgr C Cores为研究对象,利用DS9软件制作RGB三色图,并测量了云核质量、外流长度与年龄等基本物理性质。通过数据分析,探讨了云核质量与外流长度之间的关系,并使用Python绘制最小树状图,测量了云核之间的距离。研究发现,云核质量与外流长度之间无明显相关性,且周围云核的存在可能对外流的形状和长度产生影响。此外,云核之间的距离主要集中在40000个天文单位以内,推测Sgr C Cores可能在未来演化为一个疏散星团。然而,由于数据和时间的限制,本研究尚未全面探讨所有可能的影响因素,未来将致力于分析观测角度对结果的影响,并进一步验证上述结论。展开更多
Red clump(RC)stars are reliable standard candles for studying the structure and evolution of the Milky Way.In this study,we present empirical calibrations of RC absolute magnitudes in the Mephisto(v,g,r,i)and CSST(g,r...Red clump(RC)stars are reliable standard candles for studying the structure and evolution of the Milky Way.In this study,we present empirical calibrations of RC absolute magnitudes in the Mephisto(v,g,r,i)and CSST(g,r,i)photometric systems using a high-purity sample of 25,059 RC stars cross-matched between APOGEE and Gaia DR3 XP spectra.Through synthetic photometry and polynomial fitting,we find that RC absolute magnitudes exhibit strong dependencies on effective temperature and metallicity,with the strongest variations observed in bluer bands and progressively decreasing towards redder wavelengths.In particular,the Mephisto v band exhibits the highest sensitivity,with variations reaching up to 2.0 mag across the metallicity range(−1.0 dex<[Fe/H]<0.5 dex)and the temperature range(4500–5200 K).The calibrations achieve high precision for all bands,enabling accurate determination of RC absolute magnitudes and distances.Furthermore,we evaluate the metallicity estimation capabilities of both systems using a Random Forest-based method,achieving a precision of 0.12 dex for Mephisto and 0.14 dex for CSST under typical photometric uncertainties(≤0.01 mag).These results provide robust tools for distance and metallicity determinations,supporting future Galactic structure studies with Mephisto and CSST data.展开更多
Using ground-based telescopes,the multi-color photometric observations of the contact binary EF Boo were obtained in 2020,2023,and 2024.Combining these with 7-sectors of light curves from TESS data,the variations of t...Using ground-based telescopes,the multi-color photometric observations of the contact binary EF Boo were obtained in 2020,2023,and 2024.Combining these with 7-sectors of light curves from TESS data,the variations of the O'Connell effect in continuous time and shapes of light curves over several years were identified.Three sets of typical light curves were analyzed to determine the photometric solutions via the Wilson-Devinney program.Considering the spectroscopic mass ratio of q=0.53,these photometric solutions suggest that EF Boo is a W-type W UMa contact binary with the averaged filling factor of f=22.26%,a small temperature difference,and a cool spot on the primary component.If the variations of the O'Connell effect are due to the magnetic activity of this cool spot,the longitudinal location varied from 50.4 to 302.7 over the time interval of 1434 days.Based on all CCD minimum times from ground-based telescope and TESS data,the O-C curve was also analyzed.A cyclic oscillation(A3=0.00575 days,T3=27.8 yr)superimposed on a secular increase(dP/dt=6.74×10^(-8)day yr^(-1))was discovered for the first time.The successive increase is possibly a result of mass transfer from the less massive star to the more massive one.The cyclic oscillations were possibly explained by the light-travel time effect via a third body or the magnetic activities.From the short cadence observations from TESS,we also calculated the value of the O'Connell effect and O-C value for each cycle and found no correlation between the O'Connell effect and O-C over nearly 30 days across different sectors.展开更多
Based on positional observations and measurements of radial velocities,the orbits of 850 wide visual binary stars have been determined.The parameters of the log-normal distributions for the histograms of orbital perio...Based on positional observations and measurements of radial velocities,the orbits of 850 wide visual binary stars have been determined.The parameters of the log-normal distributions for the histograms of orbital periods,stellar masses,and semimajor axes in astronomical units have been obtained.The eccentricity histogram for binary stars with orbital periods less than 400 yr follows a normal distribution centered at e=0.545+/−0.029.For stars with longer periods,this distribution obeys the law f=2e,with accuracy to errors.The mass-to-luminosity relation for stars with well-determined masses is given by:log L_(⊙)=4.33 logM_(⊙)-0.11,where L_(⊙) and M_(⊙) are the luminosity and mass of the star in units of the solar luminosity and mass,respectively.展开更多
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.
文摘In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.
文摘AR Aur A+B is a close binary of astrophysical interest because dissimilar surface compositions are reported between similar late B-type dwarfs.A new spectroscopic study on this system was carried out based on the disentangled spectra,in order to determine their atmospheric parameters and elemental abundances.The effective temperature and microturbulence(determined from the equivalent widths of Fe II lines)turned out to be(11,150 K,0.9 km s^(-1))and(10,650 K,0.1 km s^(-1))for A and B,respectively.The chemical abundances of 28 elements were then derived while taking into account the non-LTE effect for Z≤15 elements(Z:atomic number).The following trends were elucidated for[X/H](abundance of X relative to the Sun):(1)Qualitatively,[X/H]shows a rough global tendency to increase with Z,with the gradient steeper for A than for B.(2)However,considerable dispersion is involved for A,since prominently large peculiarities are seen in specific elements reflecting the characteristics of HgMn stars(e.g.,very deficient N,Al,Sc,Ni;markedly overabundant P,Mn).(3)In contrast,the Z-dependence of[X/H]for B tends to be nearly linear with only a small dispersion.These observational facts may serve as a key to understanding the critical condition for the emergence of the chemical anomaly.
基金supported by the National Natural Science Foundation of China(NSFC)through grants 12173047,12373035,12322306,12373028,12233009 and 12133002X.C.and S.W.acknowledge supports from the Youth Innovation Promotion Association of the Chinese Academy of Sciences(CAS,Nos.2022055 and 2023065)+2 种基金support from the National Key Research and Development Program of China,grant 2022YFF0503404Funding for the DPAC has been provided by national institutions,in particular the institutions participating in the Gaia Multilateral AgreementFunding for the project has been provided by the National Development and Reform Commission。
文摘δScuti(δSct)stars are potential distance tracers for studying the Milky Way structure.We conduct a comprehensive analysis of the period-luminosity(PL)and period-luminosity-metallicity(PLZ)relations forδSct stars,integrating data from the Zwicky Transient Facility,the Transiting Exoplanet Survey Satellite,Large Sky Area Multi-Object Fiber Spectroscopic Telescope,Apache Point Observatory Galactic Evolution Experiment,and Gaia.To mitigate the impact of the Gaia parallax zero point offset,we applied a correction method,determining the optimal zero point value to be zp(?)=35±2μas.Using the three best bands,by varying the parallax error threshold,we found that the total error of the PLR zero point was minimized to 0.9%at a parallax error threshold of 6%.With this threshold,we derived the PL and PLZ relations for nine bands(from optical to mid-infrared)and five Wesenheit bands.Through our analysis,we conclude that the influence of metallicity on the PLR ofδSct stars is not significant,and the differences across various bands are minimal.
基金founded by the Gordon and Betty Moore Foundation through grants GBMF5490 and GBMF10501 to Ohio State Universitythe Alfred P.Sloan Foundation grant G-2021-14192
文摘We presented the first photometric light curve solutions of four W Ursae Majoris-type contact binary systems.This investigation utilized photometric data from the Transiting Exoplanet Survey Satellite and Gaia Data Release 3(DR3).We used the PHysics Of Eclipsing BinariEs Python code and the Markov Chain Monte Carlo method for these light curve solutions.Only TIC 249064185 among the target systems needed a cold starspot to be included in the analysis.Based on the estimated mass ratios for these total eclipse systems,three of them are categorized as low mass ratio contact binary stars.The absolute parameters of the systems were estimated using the Gaia DR3 parallax method and the orbital period and semimajor axis(P-a)empirical relationship.We ascertained that the TIC 318015356 and TIC 55522736 systems are A-subtypes,while TIC 249064185 and TIC 397984843 are W-subtypes,depending on each component’s effective temperature and mass.We estimated the initial masses of the stars,the mass lost by the binary system,and the systems’ages.We displayed star positions in the mass-radius,mass-luminosity,and total mass-orbital angular momentum diagrams.In addition,our findings indicate a good agreement with the mass-temperature empirical parameter relationship for the primary stars.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.12203011 and 12033005)the support by Yunnan province Xingdian talent support program,Yunnan provincial Department of Science and Technology through grant No.202101BA070001-261+8 种基金Yunnan University Laboratory Open ProjectPhD research startup foundation of Chuxiong Normal Universitythe Xinjiang Uygur Autonomous Region of China for their support through the Tianchi Programsupported by the international partnership program of Chinese Academy of Sciences through grant No.114231KYSB20200009Shanghai Pujiang Program 20PJ1415500the science research grant from the China Manned Space Project with No.CMS-CSST-2021-B06support from NSFC through grant No.12303028support from the Natural Science Foundation of Xinjiang Uygur Autonomous Region(No.2024D01E37)the NSFC(12473025).
文摘Sulfur-bearing molecules are frequently detected in star-forming regions.The abundance ratio of SO to SO_(2)(hereafter,SO/SO_(2) ratio)has been proposed as a potential evolutionary tracer of star formation because tentative correlations have been found between SO/SO_(2) ratio and evolutionary stages.Nonetheless,the lack of highresolution observations and extensive statistical analyses of large samples raises questions regarding its efficacy as an evolutionary tracer.In this study,we analyze 31 protostellar cores with both SO and SO_(2) detection to investigate the relationship between the SO/SO_(2) ratio and two evolutionary parameters of chemical richness factor and gas temperatures.The correlations between SO/SO_(2) ratio and evolutionary parameters have been found,but these correlations are mainly contributed by low-mass cores rather than high-mass cores.Our findings suggest that the SO/SO_(2) ratio serves as a reliable evolutionary tracer for low-mass dense cores.In high-mass cores,the relationship between the SO/SO_(2) ratio and evolutionary stage remains ambiguous.This likely arises from both vigorous stellar feedback effects and the potential absence of distinct evolutionary stages analogous to those in low-mass cores.Consequently,higher-resolution observations with expanded statistical samples are required to assess the viability of SO/SO_(2) ratio as an evolutionary tracer for high-mass cores.
基金supported by the National Natural Science Foundation of China12203016,12173034,12322304 and 12173013Natural Science Foundation of Hebei Province No.A2022205018,A2021205006,226Z7604G+4 种基金Yunnan University grant No.C619300A034Science Foundation of Hebei Normal University No.L2022B33.W.Y.Cacknowledges the science research grants from the China Manned Space Projectthe support of Physics Postdoctoral Research Station at Hebei Normal Universitythe science research grants from the China Manned Space Project with NOs.CMS-CSST-2021-A09,CMS-CSST-2021-A08 and CMS-CSST-2021-B03。
文摘The availability of large data sets containing stellar parameters,distances,and extinctions for stars in the Milky Way,particularly within the Galactic disk,is essential for advancing our understanding of the Galaxy’s stellar populations,structure,kinematics,and chemical evolution.In this study,we present a catalog of stellar parameters,including effective temperature (T_(eff)),metallicity ([Fe/H]),absolute magnitudes (M_(G)),distances (d),and reddening values (E(G_(BP)-G_(RP))),for a sample of 141 million stars from the SkyMapper Southern Survey.These parameters are derived using the SPar algorithm,which employs a fitting procedure to match multi-band photometric observations and estimate the stellar properties (T_(eff),[Fe/H],M_(G),d,and E(G_(BP)-G_(RP))) on an individual star basis,following the methodology outlined in our previous work.This study successfully determines stellar parameters and extinction values simultaneously for stars located in high and low Galactic latitudes.The resulting stellar parameters and extinction values are in good agreement with results from other studies,demonstrating the robustness of our method.We derive a temperature dispersion of 195 K and a metallicity dispersion of 0.31 dex when comparing our results with spectroscopic data.The catalog produced in this work provides a valuable resource for future research on the Galactic metallicity distribution function,the structure of the Galaxy,threedimensional extinction mapping,and other related astrophysical topics.
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the Natural Science Foundation of Shandong Province with grant Nos.ZR2024MA063,ZR2022MA076 and ZR2022MA089Additional support was provided by the science research grants from the China Manned Space Project with grant Nos.CMS-CSST-2021-B05 and CMS-CSST-2021-A08+1 种基金supported by the National Natural Science Foundation of China(NSFC)under grant Nos.11873037 and 11803016Furthermore,the Young Scholars Program of Shandong University,Weihai(2016WHWLJH09)provided support for this research.
文摘Hot subdwarf stars are important celestial objects in the study of stellar physics,but the population remains limited.The LAMOST DR12-V1,released in 2025 March,is currently the world’s largest spectroscopic database,holding great potential for the search of hot subdwarf stars.In this study,we propose a two-stage deep learning model called the hot subdwarf network(HsdNet),which integrates multiple advanced techniques,comprising a binary classification model in stage one and a five-class classification model in stage two.HsdNet not only achieves high precision with 94.33%and 94.00%in the binary and the five-class classification stages,respectively,but also quantifies the predicted uncertainty,enhancing the interpretability of the classification results through visualizing the model’s key focus regions.We applied HsdNet to the 601,217 spectra from the LAMOST DR12-V1 database,conducting a two-stage search for hot subdwarf candidates.In stage one,we initially identified candidates using the binary classification model.In stage two,the five-class classification model was used to further refine these candidates.Finally,we confirmed 1008 newly identified hot subdwarf stars.The distribution of their atmospheric parameters is consistent with that of known hot subdwarf stars.These efforts are expected to significantly advance the research on hot subdwarf stars.
基金support of the Strategic Priority Research Program of the Chinese Academy of Sciences under grant No.XDB0800303the National Key R&D Program of China under grant No.2022YFA1603100the National Natural Science Foundation of China(NSFC,Grant No.12203086)。
文摘We propose that the core mass function(CMF)can be driven by filament fragmentation.To model a star-forming system of filaments and fibers,we develop a fractal and turbulent tree with a fractal dimension of 2 and a Larson's law exponent(β)of 0.5.The fragmentation driven by convergent flows along the splines of the fractal tree yields a Kroupa-IMF-like CMF that can be divided into three power-law segments with exponentsα=-0.5,-1.5,and-2,respectively.The turnover masses of the derived CMF are approximately four times those of the Kroupa IMF,corresponding to a star formation efficiency of 0.25.Adoptingβ=1/3,which leads to fractional Brownian motion along the filament,may explain a steeper CMF at the high-mass end,withα=-3.33 close to that of the Salpeter IMF.We suggest that the fibers of the tree are basic building blocks of star formation,with similar properties across different clouds,establishing a common density threshold for star formation and leading to a universal CMF.
文摘在分子云中,新生恒星之间的关系复杂且多样,这些关系对恒星的形成和演化过程具有重要影响。本文以Sgr C Cores为研究对象,利用DS9软件制作RGB三色图,并测量了云核质量、外流长度与年龄等基本物理性质。通过数据分析,探讨了云核质量与外流长度之间的关系,并使用Python绘制最小树状图,测量了云核之间的距离。研究发现,云核质量与外流长度之间无明显相关性,且周围云核的存在可能对外流的形状和长度产生影响。此外,云核之间的距离主要集中在40000个天文单位以内,推测Sgr C Cores可能在未来演化为一个疏散星团。然而,由于数据和时间的限制,本研究尚未全面探讨所有可能的影响因素,未来将致力于分析观测角度对结果的影响,并进一步验证上述结论。
基金partially supported by the National Natural Science Foundation of China(NSFC,Grant Nos.12173034 and 12322304)the National Natural Science Foundation of Yunnan Province 202301AV070002+1 种基金the Xingdian talent support program of Yunnan Provincethe science research grants from the China Manned Space Project with No.CMS-CSST-2021-A09,CMS-CSST-2021-A08 and CMS-CSST-2021-B03。
文摘Red clump(RC)stars are reliable standard candles for studying the structure and evolution of the Milky Way.In this study,we present empirical calibrations of RC absolute magnitudes in the Mephisto(v,g,r,i)and CSST(g,r,i)photometric systems using a high-purity sample of 25,059 RC stars cross-matched between APOGEE and Gaia DR3 XP spectra.Through synthetic photometry and polynomial fitting,we find that RC absolute magnitudes exhibit strong dependencies on effective temperature and metallicity,with the strongest variations observed in bluer bands and progressively decreasing towards redder wavelengths.In particular,the Mephisto v band exhibits the highest sensitivity,with variations reaching up to 2.0 mag across the metallicity range(−1.0 dex<[Fe/H]<0.5 dex)and the temperature range(4500–5200 K).The calibrations achieve high precision for all bands,enabling accurate determination of RC absolute magnitudes and distances.Furthermore,we evaluate the metallicity estimation capabilities of both systems using a Random Forest-based method,achieving a precision of 0.12 dex for Mephisto and 0.14 dex for CSST under typical photometric uncertainties(≤0.01 mag).These results provide robust tools for distance and metallicity determinations,supporting future Galactic structure studies with Mephisto and CSST data.
基金support of the staff of the 85 cm,60 cm telescopes at the Xinglong observational station of the National Astronomical Observatories,Chinese Academy of Sciences,and TESS team works funding by the NASA Science Mission directorate.This work is sponsored by the Natural Science Foundation of Xinjiang Uygur Autonomous Region(No.2022D01A164)the National Natural Science Foundation of China(Nos.U1831109 and 12103030)。
文摘Using ground-based telescopes,the multi-color photometric observations of the contact binary EF Boo were obtained in 2020,2023,and 2024.Combining these with 7-sectors of light curves from TESS data,the variations of the O'Connell effect in continuous time and shapes of light curves over several years were identified.Three sets of typical light curves were analyzed to determine the photometric solutions via the Wilson-Devinney program.Considering the spectroscopic mass ratio of q=0.53,these photometric solutions suggest that EF Boo is a W-type W UMa contact binary with the averaged filling factor of f=22.26%,a small temperature difference,and a cool spot on the primary component.If the variations of the O'Connell effect are due to the magnetic activity of this cool spot,the longitudinal location varied from 50.4 to 302.7 over the time interval of 1434 days.Based on all CCD minimum times from ground-based telescope and TESS data,the O-C curve was also analyzed.A cyclic oscillation(A3=0.00575 days,T3=27.8 yr)superimposed on a secular increase(dP/dt=6.74×10^(-8)day yr^(-1))was discovered for the first time.The successive increase is possibly a result of mass transfer from the less massive star to the more massive one.The cyclic oscillations were possibly explained by the light-travel time effect via a third body or the magnetic activities.From the short cadence observations from TESS,we also calculated the value of the O'Connell effect and O-C value for each cycle and found no correlation between the O'Connell effect and O-C over nearly 30 days across different sectors.
基金support of the Russian Foundation for Basic Research under Contract No.20-02-00563A.
文摘Based on positional observations and measurements of radial velocities,the orbits of 850 wide visual binary stars have been determined.The parameters of the log-normal distributions for the histograms of orbital periods,stellar masses,and semimajor axes in astronomical units have been obtained.The eccentricity histogram for binary stars with orbital periods less than 400 yr follows a normal distribution centered at e=0.545+/−0.029.For stars with longer periods,this distribution obeys the law f=2e,with accuracy to errors.The mass-to-luminosity relation for stars with well-determined masses is given by:log L_(⊙)=4.33 logM_(⊙)-0.11,where L_(⊙) and M_(⊙) are the luminosity and mass of the star in units of the solar luminosity and mass,respectively.
