Multi-Wavelength Observation Campaign of the TeV Gamma-Ray Binary HESS J0632+057 with NuSTAR, VERITAS, MDM, and Swift

Abstract

HESS J0632+057 belongs to a rare subclass of binary systems which emits gamma-rays above 100 GeV. It stands out for its distinctive high-energy light curve, which features a sharp ``primary'' peak and broader ``secondary'' peak. We present the results of contemporaneous observations by NuSTAR and VERITAS during the secondary peak between Dec. 2019 and Feb. 2020, when the orbital phase ($\varphi$) is between 0.55 and 0.75. NuSTAR detected X-ray spectral evolution, while VERITAS detected TeV emission. We fit a leptonic wind-collision model to the multi-wavelength spectra data obtained over the four NuSTAR and VERITAS observations, constraining the pulsar spin-down luminosity and the magnetization parameter at the shock. Despite long-term monitoring of the source from Oct. 2019 to Mar. 2020, the MDM observatory did not detect significant variation in H$\alpha$ and H$\beta$ line equivalent widths, an expected signature of Be-disk interaction with the pulsar. Furthermore, fitting folded Swift-XRT light curve data with an intra-binary shock model constrained the orbital parameters, suggesting two orbital phases (at ${\varphi }_D=0.13$ and 0.37) where the pulsar crosses the Be-disk, as well as phases for the periastron (${\varphi }_0=0.30$) and inferior conjunction (${\varphi }_{\text{IFC}}=0.75$). The broad-band X-ray spectra with Swift-XRT and NuSTAR allowed us to measure a higher neutral hydrogen column density at one of the predicted disk-passing phases.

arXiv comment21 pages, 9 figures, accepted to ApJ

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Cited by in corpus (3)

• Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC, and VERITAS telescopes
• Modelling the correlated keV/TeV light curves of Be/gamma-ray binaries
• Investigation of the broadband emission of the gamma-ray binary HESS J0632+057 using an intrabinary shock model