Riemann solitons on Vaidya spacetimes

In this paper, we study some solitons on Vaidya spacetimes. We classify all of Riemann solitons, conformal Ricci solitons, and Ricci solitons on Vaidya spacetimes and show that which of them are of gradient solitons type. Also, we provide any potential vector field of Riemann solitons is Ricci bi-conformal vector field, Killing vector field, Ricci collineation vector field, and potential vector field of steady Ricci soliton.