High-energy Emissions from the Pulsar/Be Binary System PSR J2032+4127/MT91 213

Abstract

PSR J2032+4127 is a radio-loud gamma-ray-emitting pulsar; it is orbiting around a high-mass Be type star with a very long orbital period of 25 − 50years, and is approaching periastron, which will occur in late 2017/early 2018. This system comprises with a young pulsar and a Be type star, which is similar to the so-called gamma-ray binary PSR B1259-63/LS2883. It is expected therefore that PSR J2032+4127 shows an enhancement of high-energy emission caused by the interaction between the pulsar wind and Be wind/disk around periastron. Ho et al. recently reported a rapid increase in the X-ray flux from this system. In this paper, we also confirm a rapid increase in the X-ray flux along the orbit, while the GeV flux shows no significant change. We discuss the high-energy emissions from the shock caused by the pulsar wind and stellar wind interaction and examine the properties of the pulsar wind in this binary system. We argue that the rate of increase of the X-ray flux observed by Swift indicates (1) a variation of the momentum ratio of the two-wind interaction region along the orbit, or (2) an evolution of the magnetization parameter of the pulsar wind with the radial distance from the pulsar. We also discuss the pulsar wind/Be disk interaction at the periastron passage, and propose the possibility of formation of an accretion disk around the pulsar. We model high-energy emissions through the inverse-Compton scattering process of the cold-relativistic pulsar wind off soft photons from the accretion disk.

NuSTAR Hard X-Ray Observation of the Gamma-Ray Binary Candidate HESS J1832–093

“…Multi-wavelength monitoring of the gamma-ray binaries in the X-ray, GeV, and TeV bands revealed the complex emission mechanisms and geometry (Kaspi et al 1995;Chernyakova et al 2006aChernyakova et al , 2006bChernyakova et al , 2009Kishishita et al 2009;Takahashi et al 2009;Uchiyama et al 2009;Li et al 2011;An et al 2013An et al , 2015Aliu et al 2014;Ho et al 2017). A number of theoretical models, including numerical hydrodynamics simulations, have been developed to account for the orbital dependence of the X-ray and gamma-ray spectra via anisotropic radiation processes, relativistic Doppler boosting, and inhomogeneous stellar winds de la Cita et al 2017;Takata et al 2017). Studying these rare gamma-ray binaries not only probes the unique environment of the pulsar and stellar wind interaction but also sheds light on the (short) X-ray binary evolution stage before they become "regular" accretion powered high-mass X-ray binaries (HMXBs; Dubus 2013).…”

Gamma-rays from the binary system containing PSR J2032+4127 during its periastron passage

“…This luminosity corresponds to a star with the effective surface temperature, the radius, and the distance as given in Table 1 [17]. Note that the radius and the luminosity of the star are lower than those used in [10] by a factor of 7/3 and ∼ 5.4, respectively. The luminosity of the companion star which we consider is consistent with the observations of MT91 213 [17].…”

Modelling the GeV emission of HESS J0632+057

“…Takata et al 2017;Yi & Cheng 2017). The pulsar companion travels through the circumstellar disc of the main sequence star twice in each orbit, when some of the matter is gravity-captured.…”