Hour-Scale Multiwavelength Variability in Markarian 421

Authors :: Catanese, M.
Bond, I. H.
Bradbury, S. M.
Breslin, A. C.
Buckley, J. H.
Burdett, A. M.
Carter-Lewis, D. A.
Cawley, M. F.
Dunlea, S.
D'Vali, M.
Fegan, D. J.
Fegan, S. J.
Finley, J. P.
Gaidos, J. A.
Hall, T. A.
Hillas, A. M.
Horan, D.
Knapp, J.
Krennrich, F.
Bohec, S. Le
Lessard, R. W.
Masterson, C.
Moriarty, P.
Quinn, J.
Rose, H. J.
Samuelson, F. W.
Sembroski, G. H.
Vassiliev, V. V.
Weekes, T. C.
Maraschi, L.
Fossati, G.
Tavecchio, F.
Chiappetti, L.
Celotti, A.
Ghisellini, G.
Grandi, P.
Pian, E.
Tagliaferri, G.
Treves, A.
Publication Year :: 1999
Abstract: Markarian 421 was observed for about four days with BeppoSAX and the Whipple Observatory gamma-ray telescope in April 1998. A pronounced, well-defined, flare with hour-scale variability was observed simultaneously in X-rays and very high energy gamma-rays. These data provide the first evidence that the X-ray and TeV intensities are well correlated on time-scales of hours. While the rise of the flare occurred on a similar time-scale in the two wavebands, the decay of the flare was much more rapid in gamma rays, providing the first clear indication that the X-ray and gamma-ray emission may not be completely correlated in Markarian 421.<br />4 pages, 1 figure, to be published in the proceedings of the 26th ICRC (Salt Lake City, 1999)