X-ray and Radio Variabilities of PSR J2032+4127 near Periastron

TL;DR

This study reports on X-ray and radio observations of PSR J2032+4127 during its 2017 periastron, revealing flux variability, spectral changes, and flares indicative of complex pulsar-stellar interactions.

Contribution

It provides detailed multi-wavelength monitoring data of PSR J2032+4127 near periastron, highlighting spectral variability and emission mechanisms in a long-period gamma-ray binary.

Findings

X-ray spectrum hardened near periastron with increased absorption

Detected a possible spectral break at a few keV suggesting synchrotron cooling

Observed a radio and X-ray flare one week after periastron

Abstract

We present X-ray and radio monitoring observations of the gamma-ray binary PSR J2032+4127/MT91 213 during its periastron passage in late 2017. Dedicated Chandra, XMM-Newton,NuSTAR X-ray observations and VLA radio observations of this long orbit (50 years), 143 ms pulsar/Be star system clearly revealed flux and spectral variability during the passage. The X-ray spectrum hardened near periastron, with a significant decrease in the power-law photon index from \Gamma ~ 2 to 1.2 and evidence of an increased absorption column density. We identified a possible spectral break at a few keV in the spectrum that suggests synchrotron cooling. A coincident radio and X-ray flare occurred one week after periastron, which is possibly the result of the pulsar wind interacting with the Be stellar disk and generating synchrotron radiation. However, a multi-wavelength comparison indicate that the X-ray and radio spectra cannot be simply connected by a single power-law component. Hence, the emission in these two energy bands must originate from different particle populations.