We present combined photometric and spectroscopic analyses of the southern binary star PU Pup.High-resolution spectra of this system were taken at the University of Canterbury Mt.John Observatory in the years 2008 and...We present combined photometric and spectroscopic analyses of the southern binary star PU Pup.High-resolution spectra of this system were taken at the University of Canterbury Mt.John Observatory in the years 2008 and again in 2014-2015.We find the light contribution of the secondary component to be only 2%of the total light of the system in optical wavelengths,resulting in a single-lined spectroscopic binary.Recent TESS data revealed grazing eclipses within the light minima,though the tidal distortion,examined also from Hipparcos data,remains the predominating light curve effect.Our model shows PU Pup to have the more massive primary relatively close to filling its Roche lobe.PU Pup is thus approaching the rare‘fast phase’of interactive(Case B)evolution.Our adopted absolute parameters are as follows:M_(1)=4.10(±0.20)M_(⊙),M_(2)=0.65(±0.05)M_(⊙),R_(1)=6.60(±0.30)R_(⊙),R_(2)=0.90(±0.10)R_(⊙);T_(1)=11500(±500)K,T_(2)=5000(±350)K;photometric distance=186(±20)pc,age=170(±20)Myr.The less-massive secondary component is found to be significantly oversized and overluminous compared to standard main sequence models.We discuss this discrepancy referring to heating from the reflection effect.展开更多
This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by m...This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by meridional circulation and shear turbulence. The circulation carries part of the angular momentum of the accreted layers to the accretor's surface. The greater the rate of arrival of angular momentum in the accretor is, the greater this part. It is assumed that this part of the angular momentum can be removed by the disk further from the accretor. If the angular momentum in the matter entering the accretor is more than half the Keplerian value, then the angular momentum obtained by the accretor during mass exchange stage does not depend on the rate of arrival of angular momentum. The accretor may have the characteristics of a Be-star immediately after the end of mass exchange.展开更多
The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physica...The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such systems.The model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact binaries.It is necessary to test whether this model can be used for W UMa-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such systems.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.The result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries.展开更多
Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Comp...Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Compact objects in binaries with a luminous stellar companion are perfect targets for optical observations.Candidate compact objects can be achieved by monitoring the radial velocities of the companion star.However,most of the spectroscopic telescopes usually obtain stellar spectra at a relatively low efficiency,which makes a sky survey for millions of stars practically impossible.The efficiency of a large-scale spectroscopic survey,the Large Sky Area Multi-Object Fiber Spectroscopy Telescope(LAMOST),presents a specific opportunity to search for compact object candidates,i.e.,simply from the spectroscopic observations.Late-type K/M stars are the most abundant populations in our Galaxy.Owing to the relatively large Keplerian velocities in the close binaries with a K/M-dwarf companion,a hidden compact object could be discovered and followed-up more easily.In this study,compact object candidates with K/Mdwarf companions are investigated with the LAMOST low-resolution stellar spectra.Based on the LAMOST Data Release 5,we obtained a sample of 56 binaries,each containing a K/M-dwarf with a large radial velocity variation △VR>150 km s^(-1).Complemented with the photometric information from the Transiting Exoplanet Survey Satellite,we derived a sample of 35 compact object candidates,among which,the orbital periods of 16 sources were revealed by the light curves.Considering two sources as examples,we confirmed that a compact object existed in the two systems by fitting the radial velocity curve.This study demonstrates the principle and the power of searching for compact objects through LAMOST.展开更多
文摘We present combined photometric and spectroscopic analyses of the southern binary star PU Pup.High-resolution spectra of this system were taken at the University of Canterbury Mt.John Observatory in the years 2008 and again in 2014-2015.We find the light contribution of the secondary component to be only 2%of the total light of the system in optical wavelengths,resulting in a single-lined spectroscopic binary.Recent TESS data revealed grazing eclipses within the light minima,though the tidal distortion,examined also from Hipparcos data,remains the predominating light curve effect.Our model shows PU Pup to have the more massive primary relatively close to filling its Roche lobe.PU Pup is thus approaching the rare‘fast phase’of interactive(Case B)evolution.Our adopted absolute parameters are as follows:M_(1)=4.10(±0.20)M_(⊙),M_(2)=0.65(±0.05)M_(⊙),R_(1)=6.60(±0.30)R_(⊙),R_(2)=0.90(±0.10)R_(⊙);T_(1)=11500(±500)K,T_(2)=5000(±350)K;photometric distance=186(±20)pc,age=170(±20)Myr.The less-massive secondary component is found to be significantly oversized and overluminous compared to standard main sequence models.We discuss this discrepancy referring to heating from the reflection effect.
基金supported by the Ministry of Science and EducationFEUZ-2023-0019。
文摘This paper investigates the spin-up of a mass-accreting star in a close binary system passing through the first stage of mass exchange in the Hertzsprung gap. Inside an accreting star, angular momentum is carried by meridional circulation and shear turbulence. The circulation carries part of the angular momentum of the accreted layers to the accretor's surface. The greater the rate of arrival of angular momentum in the accretor is, the greater this part. It is assumed that this part of the angular momentum can be removed by the disk further from the accretor. If the angular momentum in the matter entering the accretor is more than half the Keplerian value, then the angular momentum obtained by the accretor during mass exchange stage does not depend on the rate of arrival of angular momentum. The accretor may have the characteristics of a Be-star immediately after the end of mass exchange.
基金supported by the National Natural Science Foundation of China (Grant No. 10933002)
文摘The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such systems.The model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact binaries.It is necessary to test whether this model can be used for W UMa-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such systems.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.The result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries.
基金supported by the National Natural Science Foundation of China(Grant Nos.12103047,11925301,12033006,12005192)the National Key Research and Development Program of China(Grant No.2019YFA0405000)+2 种基金the China Manned Space Project(Grant No.CMS-CSST-2021-B07)the China Postdoctoral Science Foundation(Grant Nos.2019TQ0288,2020TQ0287,2020M672255,2021M702742)the Natural Science Foundation of Henan Province of China(Grant No.212300410290)。
文摘Searching for compact objects(black holes,neutron stars,or white dwarfs)in the Milky Way is essential for understanding the stellar evolution history,the physics of compact objects,and the structure of our Galaxy.Compact objects in binaries with a luminous stellar companion are perfect targets for optical observations.Candidate compact objects can be achieved by monitoring the radial velocities of the companion star.However,most of the spectroscopic telescopes usually obtain stellar spectra at a relatively low efficiency,which makes a sky survey for millions of stars practically impossible.The efficiency of a large-scale spectroscopic survey,the Large Sky Area Multi-Object Fiber Spectroscopy Telescope(LAMOST),presents a specific opportunity to search for compact object candidates,i.e.,simply from the spectroscopic observations.Late-type K/M stars are the most abundant populations in our Galaxy.Owing to the relatively large Keplerian velocities in the close binaries with a K/M-dwarf companion,a hidden compact object could be discovered and followed-up more easily.In this study,compact object candidates with K/Mdwarf companions are investigated with the LAMOST low-resolution stellar spectra.Based on the LAMOST Data Release 5,we obtained a sample of 56 binaries,each containing a K/M-dwarf with a large radial velocity variation △VR>150 km s^(-1).Complemented with the photometric information from the Transiting Exoplanet Survey Satellite,we derived a sample of 35 compact object candidates,among which,the orbital periods of 16 sources were revealed by the light curves.Considering two sources as examples,we confirmed that a compact object existed in the two systems by fitting the radial velocity curve.This study demonstrates the principle and the power of searching for compact objects through LAMOST.
