* Astronomy

Blobrana · L

HESS J0632+057

Blobrana · L

Title: The strange case of HESS J0632+057 and the gamma-ray High Mass X-ray Binaries
Authors: G. A. Caliandro, A. B. Hill, on behalf of the Fermi-LAT collaboration

In the last decade Cherenkov telescopes on the ground and space-based \gamma-ray instruments have identified a new class of high mass X-ray binaries (HMXB), whose emission is dominated by \gamma rays. To date only five of these systems are known. All of them are detected by Cherenkov telescopes in the TeV energy range, while at GeV energies there is still one (HESS J0632+057) that has no reported detection with the Fermi-LAT. A deep search for \gamma-ray emission of HESS J0632+057 has been performed using more than 3.5 years of Fermi-LAT data. We discuss the results of this search and compare it to other \gamma-ray binary systems.

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Title: Detection of VHE Gamma-rays from HESS J0632+057 during the 2011 February X-ray outburst with the MAGIC Telescopes
Authors: The MAGIC Collaboration: J. Aleksic (1), E. A. Alvarez (2), L. A. Antonelli (3), P. Antoranz (4), M. Asensio (2), M. Backes (5), U. Barres de Almeida (6), J. A. Barrio (2), D. Bastieri (7), J. Becerra González (8), W. Bednarek (9), K. Berger (8,10), E. Bernardini (11), A. Biland (12), O. Blanch (1), R. K. Bock (6), A. Boller (12), G. Bonnoli (3), D. Borla Tridon (6), V. Bosch-Ramon (14), T. Bretz (13,27), A. Cañellas (14), E. Carmona (6,29), A. Carosi (3), P. Colin (6), E. Colombo (8), J. L. Contreras (2), J. Cortina (1), L. Cossio (15), S. Covino (3), P. Da Vela (4), F. Dazzi (15,28), A. De Angelis (15), G. De Caneva (11), E. De Cea del Pozo (16), B. De Lotto (15), C. Delgado Mendez (8,29), A. Diago Ortega (8,10), M. Doert (5), A. Domínguez (17), D. Dominis Prester (18), et al. (136 additional authors not shown)

The very high energy (VHE) \gamma-ray source HESS J0632+057 has recently been confirmed to be a \gamma-ray binary. The optical counterpart is the Be star MWC 148, and a compact object of unknown nature orbits it every ~321 d with a high eccentricity of ~0.8. We monitored HESS J0632+057 with the stereoscopic MAGIC telescopes from 2010 October to 2011 March and detected significant VHE \gamma-ray emission during 2011 February, when the system exhibited an X-ray outburst. We find no \gamma-ray signal in the other observation periods when the system did not show increased X-ray flux. Thus HESS J0632+057 exhibits \gamma-ray variability on timescales of the order of one to two months possibly linked to the X-ray outburst that takes place about 100 days after the periastron passage. Furthermore our measurements provide for the first time the \gamma-ray spectrum down to about 140 GeV and indicate no turnover of the spectrum at low energies. We compare the properties of HESS J0632+057 with the similar \gamma-ray binary LS I +61 303, and discuss on the possible origin of the multi-wavelength emission of the source

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Title: Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J0632+057
Authors: VERITAS Collaboration: V. A. Acciari, E. Aliu, T. Arlen, M. Beilicke, W. Benbow, D. Boltuch, S. M. Bradbury, J. H. Buckley, V. Bugaev, K. Byrum, A. Cannon, A. Cesarini, A. Cesarini, Y. C. Chow, L. Ciupik, P. Cogan, R. Dickherber, C. Duke, T. Ergin, A. Falcone, S. J. Fegan, J. P. Finley, G. Finnegan, P. Fortin, L. Fortson, A. Furniss, K.Gibbs, G. H. Gillanders, J. Grube, R. Guenette, G. Gyuk, D. Hanna, J. Holder, D. Horan, C. M. Hui, T. B. Humensky, A. Imran, P. Kaaret, N. Karlsson, M. Kertzman, D. Kieda, J. Kildea, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, G. Maier, A. McCann, M. McCutcheon, J. Millis, P. Moriarty, R. Mukherjee, R. A. Ong, A. N. Otte, D. Pandel, J. S. Perkins, D. Petry, M. Pohl, J. Quinn, K. Ragan, L. C. Reyes, P. T. Reynolds, H. J. Rose, M. Schroedter,
G. H. Sembroski, A. W. Smith, D. Steele, M. Theiling, J. A. Toner, A. Varlotta, V. V. Vassiliev, S. Vincent, R. G. Wagner, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, T. Weisgarber, D. A. Williams, S. Wissel, M. Wood
et al. (17 additional authors not shown)

HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057 was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these observations, no significant signal in gamma rays with energies above 1 TeV was detected from the direction of HESS J0632+057. A flux upper limit corresponding to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data. The non-detection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with Swift XRT reveal a factor of 1.8±0.4 higher flux in the 1-10 keV range than earlier X-ray observations of HESS J0632+057. The variability in the gamma-ray and X-ray fluxes supports interpretation of the object as a gamma-ray emitting binary.

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