Gravitational Redshift for Wide Binaries in Gaia eDR3

Abstract

Abstract The Doppler effect is commonly used to infer the velocity difference between stars based on the relative shifts in the rest-frame wavelengths of their spectral features. In wide binaries, the difference in gravitational redshift from the surfaces of the constituent stars with distinct compactness dominates at separations ≳10−2 pc. I suggest that this effect became apparent for wide pairs in the Gaia eDR3 catalog but was incorrectly interpreted as a possible modification of Newtonian gravity in the internal kinematics of very wide binaries.