Hour-Scale Multiwavelength Variability in Markarian 421

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.

Hour-Scale Multiwavelength Variability in Markarian 421

Authors

Description

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.
4 pages, 1 figure, to be published in the proceedings of the 26th ICRC (Salt Lake City, 1999)