Hard X-ray variability of three active galactic nuclei

Details Hard X-ray variability of three active galactic nuclei Hard X-ray variability of three active galactic nuclei

Sep 1984

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984apj...284...54u&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 284, Sept. 1, 1984, p. 54-59.

Astronomy and Astrophysics

Astrophysics

16

Active Galactic Nuclei, Astronomical Spectroscopy, Bl Lacertae Objects, Seyfert Galaxies, X Ray Sources, Balloon-Borne Instruments, Proportional Counters, Spectral Energy Distribution

Scientific paper

Spectral observations of three active galactic nuclei (AGN) in the hard X-ray range between 20 and 100 keV are reported. The data include two Seyfert galaxies (MCG 8-11-11 and NGC 4151) and the BL Lac object Mrk 421. The observational results were obtained with a large-area balloon-borne telescope consisting of a one sq m. array of multiwire Spectroscopic Proportional Counters (SPCs). The observations show that the Seyfert galaxies exhibit very flat hard X-ray spectra which can be fitted with a power law with photo indices of about 1.4 and 1.1, respectively. Flux measurements for NGC 4151 are found, to be in agreement with measurements from the literature. The source shows an integral flux value of a factor of about 4 lower than preflare measurements made during the HEAO 1 A-2 experiment in 1980 in the 20-200 keV energy range. Mrk 421 showed a flatter spectrum with a power law photon index of about 0.85, confirming its spectral shape variability. A comparison of these spectral measurements with earlier data confirmed the long-term variability of the AGNs in terms of integral intensity.

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