Probing the Properties of the Pulsar Wind in the Gamma-Ray Binary HESS J0632+057 with NuSTAR and VERITAS Observations

Abstract

HESS J0632+057 is a gamma-ray binary composed of a compact object orbiting a Be star with a period of about $315$ days. Extensive X-ray and TeV gamma-ray observations have revealed a peculiar light curve containing two peaks, separated by a dip. We present the results of simultaneous observations in hard X-rays with NuSTAR and in TeV gamma-rays with VERITAS, performed in November and December 2017. These observations correspond to the orbital phases $\varphi \approx 0.22$ and $0.3$, where the fluxes are rising towards the first light-curve peak. A significant variation of the spectral index from 1.77$\pm$0.05 to 1.56$\pm$0.05 is observed in the X-ray data. The multi-wavelength spectral energy distributions (SED) derived from the observations are interpreted in terms of a leptonic model, in which the compact object is assumed to be a pulsar and non-thermal radiation is emitted by high-energy electrons accelerated at the shock formed by the collision between the stellar and pulsar wind. The results of the SED fitting show that our data can be consistently described within this scenario, and allow us to estimate the magnetization of the pulsar wind at the location of the shock formation. The constraints on the pulsar-wind magnetization provided by our results are shown to be consistent with those obtained from other systems.

Accepted for publication in The Astrophysical Journal

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Cited by in corpus (6)

• NuSTAR observation of LS 5039
• Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes
• Multi-Wavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632+057 with NuSTAR, VERITAS, MDM, and Swift
• Multi-wavelength observations of 2HWC J1928+177: dark accelerator or new TeV gamma-ray binary?
• Radius, rotational period and inclination of the Be stars in the Be/gamma-ray binaries MWC 148 and MWC 656
• X-ray imaging observations of the high-mass gamma-ray binary HESS J0632+057