Multi-wavelength Study of HESS J0632+057: New Insights into Pulsar-Disk Interaction

TL;DR

This study analyzes multi-wavelength data of the gamma-ray binary HESS J0632+057, revealing orbital and short-term variability in X-ray and TeV emissions, offering new insights into pulsar-disk interactions and shock emission mechanisms.

Contribution

The paper provides new multi-wavelength observations that confirm orbital variability and reveal independent flux variations, advancing understanding of pulsar-disk interactions in gamma-ray binaries.

Findings

Confirmed orbital variability in X-ray spectrum.

Detected short-term X-ray flux variations under 3 days.

Observed independent variability in X-ray and TeV fluxes.

Abstract

We present an analysis of new multi-wavelength observations of the TeV gamma-ray binary HESS J0632+057, conducted using SALT, Swift, NuSTAR, and VERITAS in 2023--2024. By combining these new data with archival observations, we confirm previous suggestions of orbital variability in the source's X-ray spectrum, including increased X-ray absorption at the orbital phase interval of $\phi\approx0.3\textrm{--}0.4$. The source's X-ray flux within this phase interval seems to have exhibited a significant change on an orbital timescale. Additionally, occasional short-term variations in the X-ray band on a timescale of less than 3 days have been observed. The measured duration of the increased absorbing column density and the flux variability timescales can provide clues about the interaction between the putative pulsar and the Be companion's disk if, as previously suggested, the pulsar crosses the disk at this phase interval. Moreover, the new contemporaneous X-ray and TeV observations around the pulsar-crossing phases revealed independent variability in the X-ray and TeV fluxes, contrary to a previous observation of concurrent flux increases. While these observations alone cannot provide definitive conclusions, we discuss our results in the context of pulsar-disk interaction and intrabinary shock emission scenarios.