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The gamma-ray binary HESS J0632+057 is in an unusually high X-ray and TeV emission state.

ATel #11223; Reshmi Mukherjee (Barnard College) for the VERITAS Collaboration
on 24 Jan 2018; 22:05 UT
Credential Certification: Reshmi Mukherjee (muk@astro.columbia.edu)

Subjects: Gamma Ray, TeV, VHE, Binary

Referred to by ATel #: 11233, 11257

Observations by the VERITAS collaboration and with the Swift XRT show the TeV and X-ray emission of the gamma-ray binary HESS J0632+057 (RA 06h32m59.26s, Dec +05d48m01.2s, J2000.0) are comparable to the highest ever observed from this object. HESS J0632+057 (VER J0633+057 in the VERITAS catalog) is associated with the B0pe star MWC 148 and the X-ray source XMMU J063259.3+054801, and has also been weakly detected at GeV energies. The binary orbital period is 315 days, and the nature of the compact object is unknown. Correlated X-ray and TeV flares have been observed in the past, usually peaking around orbital phase 0.35. The system is currently at phase 0.42. Observations made with VERITAS on MJDs 58136 and 58141 detect the source with a statistical significance in excess of 10 standard deviations in an exposure of 4.3 hours. The integral gamma-ray flux is 5.9e-12 ± 7.7e-13 photons cm^-2 s^-1 above 350 GeV (corresponding to about 6% of the flux of the Crab Nebula above the same energy), about twice the flux typically measured in this orbital phase range. Swift XRT observations on MJD 58142 show a 0.3-10 keV count rate of 0.060 ± 0.007.

We encourage multi-wavelength observations. VERITAS observations will continue until Sep 26th, but will not be possible over the following full Moon period. Questions regarding VERITAS should be directed to Reshmi Mukherjee (rmukherj@nevis.columbia.edu). The VERITAS array is located at the Fred Lawrence Whipple Observatory in southern Arizona, USA (http://veritas.sao.arizona.edu). This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.