BeppoSAX Observations of Markarian 501 in June 1999
Abstract
We present the preliminary results of a long BeppoSAX observation of the BL Lac object Mkn501 carried out in June 1999. The source was fainter than found during the BeppoSAX pointings of 1997 and 1998, but is still detected with a good signal-to-noise ratio up to ~40 keV. The X-ray spectrum in the energy range 0.1-40 keV, produced through synchrotron radiation, is steeper than in the previous years, it is clearly curved, and peaks (in nu*F_nu) at ~0.5 keV. This energy is much lower than those at which the synchrotron component was found to peak in 1997 and 1998. Some intraday variability suggests that activity of the source on small time scales accompanies the large long time scale changes of brightness and spectrum.
Cite
@article{arxiv.astro-ph/0007268,
title = {BeppoSAX Observations of Markarian 501 in June 1999},
author = {E. Pian and L. Chiappetti and P. Giommi and F. Tavecchio and L. Maraschi and E. Palazzi and F. Aharonian and M. Catanese and A. Celotti and B. Degrange and A. Djannati-Atai and G. Fossati and G. Ghisellini and H. Krawczynski and C. M. Raiteri and R. M. Sambruna and D. Smith and G. Tagliaferri and G. Tosti and A. Treves and C. M. Urry and M. Villata},
journal= {arXiv preprint arXiv:astro-ph/0007268},
year = {2009}
}
Comments
4 pages, Latex, 2 PostScript figures, to appear in the Proceedings of the Conference "X-ray Astronomy '999: Stellar Endpoints, AGNs, and the Diffuse X-ray Background" (Bologna, 6-10 September 1999)