Multiwavelength monitoring and X-ray brightening of Be X-ray binary PSR J2032+4127/MT91 213 on its approach to periastron

Abstract

The radio and gamma-ray pulsar PSR J2032+4127 was recently found to be in a decadeslong orbit with the Be star MT91 213, with the pulsar moving rapidly towards periastron. This binary shares many similar characteristics with the previously unique binary system PSR B1259−63/LS 2883. Here, we describe radio, X-ray, and optical monitoring of PSR J2032+4127/MT91 213. Our extended orbital phase coverage in radio, supplemented with Fermi LAT gamma-ray data, allows us to update and refine the orbital period to 45-50 yr and time of periastron passage to 2017 November. We analyse archival and recent Chandra and Swift observations and show that PSR J2032+4127/MT91 213 is now brighter in X-rays by a factor of ∼ 70 since 2002 and ∼ 20 since 2010. While the pulsar is still far from periastron, this increase in X-rays is possibly due to collisions between pulsar and Be star winds. Optical observations of the Hα emission line of the Be star suggest that the size of its circumstellar disc may be varying by ∼ 2 over timescales as short as 1-2 months. Multiwavelength monitoring of PSR J2032+4127/MT91 213 will continue through periastron passage, and the system should present an interesting test case and comparison to PSR B1259−63/LS 2883.

Gamma–Gamma Absorption in the γ-ray Binary System PSR B1259-63/LS 2883

“…This source has been detected by Fermi-LAT but, unlike the other sources, has not been detected at TeV energies. One other candidate γ-ray binary system, PSR J2032+4127/MT91 213, which contains a γ-ray pulsar, has also recently been highlighted by Ho et al (2017). A possible TeV counterpart of this binary system, TeV J2032+4130, was one of the first sources ever detected at TeV energies and the first TeV source with no obvious counterpart at other wavelengths (Aharonian et al 2002).…”

“…The source, however, exhibits a steady TeV flux with no evidence of periodic behaviour and was at first suggested to be the evolved pulsar wind nebula of PSR J2032+4127 (Aliu et al 2014, and references therein). The recent discovery that the pulsar is in a ∼ 30 year orbit around MT91 213, and is expected to pass through periastron by the end of 2017, challenges the current interpretation (Lyne et al 2015;Ho et al 2017).…”

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

“…Other scenarios such as the microquasar model (Romero et al 2003;Bosch-Ramon & Paredes 2004) are less plausible since the spectral and timing properties are similar in all TeV gamma-ray binaries, including the two containing radio pulsars (Dubus 2013). 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).…”

Recent Galactic Science Results from VERITAS on Pulsar Searches, PSR J2032+4127, and HAWC Follow-Ups

“…The X-ray flux from J2032 has been rising for some time, with an increase by a factor of 70 since 2002 (as of 2016 May) reported in [14]. This brightening has been interpreted as a result of increasing collisional wind energy in the shock region formed by the pulsar and stellar winds [14].…”