The orbital parameters of gamma-ray binary PSR~J2032+4127

Abstract

PSR~J2032+4127 is the only one of gamma-ray binary, that exhibits pulsations in gamma-ray. Previous research has indicated that the pulsar and the Be star MT91 213 orbit each other in a highly eccentric orbit with an extremely long period, with the pulsar reaching its periastron on November 13, 2017. Since its launch, the \fermi{} satellite has been monitoring this pulsar for 16 years, covering the 8 years before and the 8 years after the pulsar passed its periastron. Using these data, we present an analysis of pulse arrival times, and precisely determine the orbital parameters for the first time: the orbital period of $P_{\mathrm{orb}}\sim 52.3$ yr, the eccentricity of $e\sim 0.98$, the semimajor axis of $a$sin$i\sim 25.3$ AU, and the orbital inclination of $\sim$ 47.1${}^{\circ }$ -- 55.1${}^{\circ }$. We also reveal another small glitch occurred in 2021, MJD $\sim$ 59500.

7 pages, 3 figure, 2 tables, accepted for publication in ApJ