Study Of The OB And Special Stars From LAMOST DR7 Data

Massive stars are the main sources of the chemical elements of the universe.and they play important roles in the evolution of their host galaxies.OB stars(stars with spectral types of O or B),as typical young massive stars,are the main probe in studying the star formation region(SFR)and molecular clouds(GC)of the Milky Way.Be stars as a special kind of B-type stars play significant roles in the study of the internal physical process of highly evolved stars.WD and sd OB stars as low-and intermediate-mass stars provide important data resources for investigating the mechanisms of star formation,evolution,as well as determining the ages of clusters,Galactic disk and halo.As the highest temperature stars,OB stars usually located on the upper left corner of the Hertzsprung-Russell diagram(HRD),and play key roles in the studies of the Milky Way evolution and cosmology structure.By analyzing the spectra of identified OB stars,the characteristics of OB stars that distinguish them from other types stars were obtained.And based on this,the work that searching for more OB stars of our group(Liu et al.2019)are pushed forward to the two new additional spectra libraries of LAMOST DR6 and DR7.Using the line index of stellar spectra,4878 new OB stars were eventually discovered,including 32 O-type stars,4105 B-type stars,58 WD stars,214 sd OB stars,and 469 Be stars(in total 1680 Be stars are found,but 1211stars among them have been discovered in Liu et al.2019).This work largely increased the number of known OB stars.But to confirm the validity of the sample,by deriving their location in the Cartesian space(X,Y,Z)and the relative velocity of UVW and V_ZV_RV_?,we also studied the location of these stars in the space,and the result show that the young OB(including Be stars)are mostly located on the galactic disk,while WD and sd OB stars are also ocated on the galactic disk,mainly due to the limitation of the LAMOST telescope observation capability.Besides of that,we also examined the location of these stars in the HRD,and the result is also consistent with the theoretical perception,indicating that the identification of OB stars in this work is acceptable.