X-ray and radio variabilities of PSR J2032+4127 near 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 indicates 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.

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ORCID for Wynn C.G. Ho: orcid.org/0000-0002-6089-6836

ORCID for Malcolm J. Coe: orcid.org/0000-0002-0763-8547

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