Speaker
Description
Gamma-ray binaries exhibit variable high-energy emission driven by interactions between a compact object and its massive stellar companion. Their orbitally modulated emission provides an opportunity to investigate particle acceleration under dynamically changing astrophysical conditions. HESS J0632+057, discovered by the High Energy Stereoscopic System (H.E.S.S.) in 2007, is a Galactic gamma-ray binary with a known orbital period of approximately 315 days.
In this work, we perform a time-dependent analysis of HESS J0632+057 using 2,886 days of data collected by the High Altitude Water Cherenkov (HAWC) observatory. HAWC is a ground-based gamma-ray detector located in Mexico that continuously monitors the overhead sky with a wide field of view (~2 sr) and a duty cycle exceeding 95%. These characteristics make HAWC particularly well suited for long-term studies of variable sources. Using nearly eight years of continuous observations, we achieve uniform phase coverage over multiple orbital cycles, enabling a consistent comparison of emission states and a search for orbital modulation in the very-high-energy (VHE) regime.
We divide the dataset according to the orbital phase of HESS J0632+057 into four emission states, namely, first high state, low state, second high state, and medium state, and construct phase-folded sky maps for each interval. We observe enhanced gamma-ray emission during the two high states. We report the corresponding VHE gamma-ray flux measurements as well as flux upper limits for the low and medium states. We also compare them with phase-resolved results from imaging atmospheric Cherenkov telescopes. In addition, we examine the spectral properties to search for evidence of phase-dependent spectral variability.
