Use The OB Star To Trace The Spiral Arm Structure Near The Sun

GAIA released the second data set(GAIA DR2)in April 2018,which contains parallax and proper motions for a large number of OB stars.From these data,we studied the structure of the spiral arm in the solar neighborhood revealed by the GAIA DR2 and compared it with the results of the VLBI masers.In this paper,we have selected three different samples to study by limiting the distance error,stellar spectral type,and peculiar motion.We found that the structure shown by GAIA DR2 in the solar neighborhood agree with the results of the VLBI maser;the result of GAIA DR2 extends the spiral arm defined by the VLBI maser to the fourth quadrant;and suggests a spur between the Local and Sagittarius arms.