GeV Detection of HESS J0632+057

Jian Li, Diego F. Torres, K. S. Cheng, Emma De Oña Wilhelmi, Peter Kretschmar, Xian Hou, Jumpei Takata

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    © 2017. The American Astronomical Society. All rights reserved. HESS J0632+057 is the only gamma-ray binary that has been detected at TeV energies, but not at GeV energies yet. Based on nearly nine years of Fermi Large Area Telescope (LAT) Pass 8 data, we report here on a deep search for the gamma-ray emission from HESS J0632+057 in the 0.1-300 GeV energy range. We find a previously unknown gamma-ray source, Fermi J0632.6+0548, spatially coincident with HESS J0632+057. The measured flux of Fermi J0632.6+0548 is consistent with the previous flux upper limit on HESS J0632+057 and shows variability that can be related to the HESS J0632+057 orbital phase. We propose that Fermi J0632.6+0548 is the GeV counterpart of HESS J0632+057. Considering the Very High Energy spectrum of HESS J0632+057, a possible spectral turnover above 10 GeV may exist in Fermi J0632.6+0548, as appears to be common in other established gamma-ray binaries.
    Original languageEnglish
    Article number169
    JournalAstrophysical Journal
    Issue number2
    Publication statusPublished - 10 Sep 2017


    • X-rays: individual (HESS J0632+057)
    • gamma-rays: stars


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