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Date and Time of the Query: 2019-06-18 T13:25:16 PDT
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For refcode 1992A&A...264...22L:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1992A&A...264...22L SIGMA observations of the Virgo cluster F. Lebrun, J. Ballet, J. Paul, P. Laurent, E. Jourdain, L. Bassani, J.-P. Roques, P. Mandrou, A. Finogenov, R. Sunyaev, E. Churazov, M. Gilfanov, N. Khavenson, V. Kovtunenko, R. Kremnev, K. Sukhanov Service d'Astrophysique, Centre d'Eludes Nucleaires de Saclay, F-91 191 Gif-sur-Yvette Cedex, France Centre d'Etude Spatiale des Rayonnements, 9 Av du Colonel Roche, BP 4346, F-3 1029 Toulouse Cedex, France Space Research Institute, Profsouznaya, 84/32, 117810 Moscow, Russia Lavotchkin Association, Khimki, Moscow District, Russia Received June 1, accepted June 10, 1992 Abstract. The Virgo cluster has been observed 10 times by the hard X-ray/soft gamma-ray telescope SIGMA for a total of about 130 useful hours. It is found that M87 is not visible at hard X-ray energies nor any of the well known X-ray and radio sources (M86, M84, NGC4438), except the Seyfert 2 galaxy NGC 4388 close to the limit of visibility (2.2 10^-5^ ph cm^-2^ s^-1^ keV^-1^ at 3 sigma at 60 keV). Together with previous observations, our result implies that NGC4388 is variable and can account alone for the whole cluster emission above 40 keV. Key words: gamma rays : general - X-rays : general - clusters of galaxies - galaxies : active - galaxies : Seyfert - galaxies : individual : NGC 4388
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