COMPTEL observations of the gamma-ray blazar PKS 1622-297

Landessternwarte Heidelberg, K¨onigstuhl, D-69117 Heidelberg, GermanyReceived November 6, 2001 / Accepted February 19, 2002Abstract. We report results of observations and analyses on the γ-ray blazar PKS 1622-297, with emphasis on theCOMPTEL data (0.75 - 30 MeV) collected between April 1991 and November 1997. PKS 1622-297 was detectedas a source of γ-rays by the EGRET experiment aboard CGRO in 1995 during a γ-ray outburst at energies above100 MeV lasting for five weeks. In this time period the blazar was significantly (∼ 5.9 σ) detected by COMPTELat 10-30 MeV. At lower COMPTEL energies the detection is marginal, resulting in a hard MeV spectrum. Thecombined 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 timeof this flare, suggesting a possible time delay with respect to the emission above 100 MeV. Outside the 5-weekflaring 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