Volume 386, Number 3, May II 2002
|Page(s)||843 - 853|
|Section||Cosmology (including clusters of galaxies)|
|Published online||15 May 2002|
COMPTEL observations of the gamma-ray blazar PKS 1622-297
Max-Planck-Institut für extraterrestrische Physik, PO Box 1603, 85740 Garching, Germany
2 Laboratory of Cosmic Ray and High Energy Astrophysics, Institute of High Energy Physics, PO Box 918-3, Beijing 100039, China
3 Astrophysics Division, Space Science Department of ESA/ESTEC, 2200 AG Noordwijk, The Netherlands
4 SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
5 University of New Hampshire, Institute for the Study of Earth, Oceans and Space, Durham NH 03824, USA
6 NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
7 Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany
Corresponding author: S. Zhang, firstname.lastname@example.org
Accepted: 19 February 2002
We report results of observations and analyses on the γ-ray blazar PKS 1622-297, with emphasis on the COMPTEL data (0.75–30 MeV) collected between April 1991 and November 1997. PKS 1622-297 was detected as a source of γ-rays by the EGRET experiment aboard CGRO in 1995 during a γ-ray outburst at energies above 100 MeV lasting for five weeks. In this time period the blazar was significantly (~5.9 σ) detected by COMPTEL at 10–30 MeV. At lower COMPTEL energies the detection is marginal, resulting in a hard MeV spectrum. The combined COMPTEL/EGRET energy spectrum shows a break at MeV energies. The broad-band spectrum (radio – γ-rays) shows that the γ-ray emission dominates the overall power output. On top of the 5-week γ-ray outburst, EGRET detected a huge flare lasting for >1 day. Enhanced MeV emission (10–30 MeV) is found near the time of this flare, suggesting a possible time delay with respect to the emission above 100 MeV. Outside the 5-week flaring period in 1995, we do not detect MeV emission from PKS 1622-297.
Key words: γ rays: observations / galaxies: active / galaxies: quasars: individual: PKS 1622-297
© ESO, 2002
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