X-RAY SPECTRAL EVOLUTION OF MKN421 IN A VERY HIGH STATE.

Authors :: Malizia, A.
Fiore, F.
Antonelli, L. A.
Giommi, P.
Capalbi, M.
Tesseri, A.
Gandolfi, G.
Rebecchi, S.
Ricci, D.
Di Ciolo, L.
Celidonio, G.
Ricci, R.
Torroni, V.
Spoliti, G.
Smith, M.
Muller, J. M.
Butler, R. C.
Piro, L.
Source :: Astrophysical Letters & Communications; Dec99 Pt 2, Vol. 39 Issue 1-6, p537, 4p, 3 Graphs
Publication Year :: 1999
Abstract: ABSTRACT Preliminary results from a BeppoSAX NFI observation of Mkn421 in a very bright state are reported together with monitoring data collected with the BeppoSAX-WFC and the RXTE-ASM. The BeppoSAX observation was carried out as part of a Target Of Opportunity program aimed at the study of AGN near record level intensity states. The comparison of our results with those of previous observations of Mkn421 shows clear evidence for strong spectral evolution. [ABSTRACT FROM AUTHOR]