Evidence for Long-Term Gamma-Ray and X-Ray Variability from the Unidentified TeV Source HESS J0632+057

• Published in: Astrophysical journal. Letters 2009-06, Vol.698 (2), p.L94-L97
• Main Authors: Acciari, V. A, Aliu, E, Arlen, T, Beilicke, M, Benbow, W, Boltuch, D, Bradbury, S. M, Buckley, J. H, Bugaev, V, Byrum, K, Cannon, A, Cesarini, A, Chow, Y. C, Ciupik, L, Cogan, P, Dickherber, R, Duke, C, Ergin, T, Falcone, A, Fegan, S. J, Finley, J. P, Finnegan, G, Fortin, P, Fortson, L, Furniss, A, Gibbs, K, Gillanders, G. H, Grube, J, Guenette, R, Gyuk, G, Hanna, D, Holder, J, Horan, D, Hui, C. M, Humensky, T. B, Imran, A, Kaaret, P, Karlsson, N, Kertzman, M, Kieda, D, Kildea, J, Konopelko, A, Krawczynski, H, Krennrich, F, Lang, M. J, LeBohec, S, Maier, G, McCann, A, McCutcheon, M, Millis, J, Moriarty, P, Mukherjee, R, Ong, R. A, Otte, A. N, Pandel, D, Perkins, J. S, Petry, D, Pohl, M, Quinn, J, Ragan, K, Reyes, L. C, Reynolds, P. T, Rose, H. J, Schroedter, M, Sembroski, G. H, Smith, A. W, Steele, D, Swordy, S, Theiling, M, Toner, J. A, Varlotta, A, Vassiliev, V. V, Vincent, S, Wagner, R. G, Wakely, S. P, Ward, J. E, Weekes, T. C, Weinstein, A, Weisgarber, T, Williams, D. A, Wissel, S, Wood, M
• Format: Article
• Language: English
• ISSN: 1538-4357; 0004-637X; 2041-8205; 1538-4357
• DOI: 10.1088/0004-637X/698/2/L94

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 hr 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 nondetection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with the Swift X-Ray Telescope 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.