Electronic Journal of Differential Equations, Vol. 2019 (2019), No. 73, pp. 1-12. Title: Travelling solitary waves for boson stars Authors: Guoqing Zhang (Univ. of Shanghai for Science and Tech., Shanghai, China) Ningning Song (Univ. of Shanghai for Science and Tech., Shanghai, China) Abstract: In this article, we study the pseudo-relativistic Hartree equation $$ i\partial_{t}\psi=(\sqrt{-\Delta+m^2}-m)\psi -(\frac{e^{-\mu|x|}}{4\pi|x|}\ast|\psi|^2)\psi,\quad \text{on }\mathbb{R}^3, $$ which describes the dynamics of pseudo-relativistic boson stars with rest mass $m>0$ in the mean-field limit. Based on Ekeland variational principle, concentration-compactness lemma and Gagliardo-Nirenberg inequality, we prove existence of travelling solitary waves under the critical stellar mass. In addition to their existence, we obtain orbital stability by using a general idea presented in Cazenave and Lions [2]. Submitted July 3, 2018. Published May 28, 2019. Math Subject Classifications: 35Q40, 35Q55, 47J35. Key Words: Travelling solitary wave; boson star equation; critical stellar mass.