Measuring the Absolute Total Intrinsic Redshifts (Surface Gravity Plus the Convective Blueshift) of the Main-sequence Stars and Red Giants using Gaia Data

Abstract

We analyze the GAIA release II data to demonstrate how one can measure the absolute total intrinsic redshifts of the main-sequence stars and red giants. We remove the relative velocity components of the stars’ motion with respect to the Sun by doing the analysis in the local standard of the rest frame defined by the average stars’ motion. We provide results for four different types of stars. F-, G-, and K-type stars have about the same value of intrinsic redshift, which is, however, much smaller than the expected gravitational redshift. This indicates that GAIA ’s data includes a convective blueshift effect of a several hundred m s −1 magnitude. The red giants’ intrinsic redshifts are negative, which implies that their convective blueshift is stronger than the gravitational redshift. This is expected since red giants are far less compact than other types.