Observation of binary systems at very-high energies with VERITAS

TL;DR

This paper reports new high-sensitivity VERITAS observations of gamma-ray binary systems LS I +61 303 and HESS J0632+057, providing insights into their variable very-high energy emission and discussing implications with X-ray and gamma-ray data.

Contribution

It presents the most sensitive VERITAS observations to date of these binaries, with dense temporal coverage, enhancing understanding of their VHE emission mechanisms.

Findings

Detection of variable VHE gamma-ray emission from LS I +61 303 and HESS J0632+057.

Correlated X-ray and gamma-ray activity observed, suggesting linked emission processes.

Implications for physical models of gamma-ray binaries discussed.

Abstract

Non-thermal variable emission from radio to very-high energy gamma rays (VHE; >100 GeV) are the prime characteristics of gamma-ray binaries. The underlying physical processes leading to the observed VHE emission are not well understood, as even the most basic features of these systems are under dispute (microquasar model vs shocked pulsar wind model). VHE binaries can be difficult to observe, some have orbital periods of the order of years (e.g. HESS J0632+057 or PSR B1259-69) or show irregular emission patterns as observed in LS I +61 303. We present here new VERITAS observations of the binary systems LS I +61 303 and HESS J0632+057 carried out with higher sensitivity and more dense temporal coverage than previous observations. The gamma-ray results and their astrophysical implications are discussed in the context of contemporaneous observations with Swift XRT and Fermi LAT at X-ray and gamma-ray energies.