A new TeV binary: The discovery of an orbital period in HESS J0632+057

S. D. Bongiorno, A. D. Falcone, M. Stroh, J. Holder, J. L. Skilton, J. A. Hinton, N. Gehrels, J. Grube

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HESS J0632+057 is a variable, point-like source of very high energy (>100GeV) gamma rays located in the Galactic plane. It is positionally coincident with a Be star, it is a variable radio and X-ray source, has a hard X-ray spectrum, and has low radio flux. These properties suggest that the object may be a member of the rare class ofTeV/X-ray binary systems. The definitive confirmation of this would be the detection of a periodic orbital modulation of the flux at any wavelength. We have obtained Swift X-Ray Telescope observations of the source from MJD 54857 to 55647 (2009 January-2011 March) to test the hypothesis that HESS J0632+057 is an X-ray/TeV binary. We show that these data exhibit flux modulation with a period of 321±5 days and we evaluate the significance of this period by calculating the null hypothesis probability, allowing for stochastic flaring. This periodicity establishes the binary nature of HESS J0632+057.

Original languageEnglish (US)
Article numberL11
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Aug 10 2011

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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