Broad-band X-ray observations of NGC 4151. by the ART-P and SIGMA telescopes in 1990-92.
Abstract
During GRANAT operation in 1990-92, a total of 35 and 207 hours of NGC 4151 observations were accumulated by the ART-P and SIGMA telescopes, respectively. The steep spectrum of NGC 4151 in hard X-rays, first detected by SIGMA in 1990 (Jourdain et al. 1992), was also found in later SIGMA observations. Comparing the results of quasi simultaneous observations of the ART-P, SIGMA and OSSE telescopes in July 1991 showed that the spectrum exhibits at least two breaks at energies above 8keV. The broad band spectrum can be satisfactorily described by a model with exponential cut-off above E~50keV. This result argues in favor of a thermal origin of the hard X-ray emission from the source. We further note that the spectrum of NGC 4151 observed by GRANAT meets the requirements for potential sources constituting the cosmic X-ray background in the 3-100keV band.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1995
- Bibcode:
- 1995A&A...300..101F
- Keywords:
-
- GALAXIES: NGC 4151;
- SEYFERT;
- DIFFUSE RADIATION;
- GAMMA-RAYS: OBSERVATIONS;
- X-RAYS: GALAXIES