The X-ray flux and spectral variability of the Einstein Extended Medium Sensitivity Survey AGN

Details The X-ray flux and spectral variability of the Einstein Extended Medium Sensitivity Survey AGN The X-ray flux and spectral variability of the Einstein Extended Medium Sensitivity Survey AGN

Dec 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997mnras.292..338c&link_type=abstract

Monthly Notices of the Royal Astronomical Society, vol. 292, p. 338

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Active Galactic Nuclei, X Ray Sources, Rosat Mission, Spectral Sensitivity, Line Of Sight, Particle Flux Density, Variability, Computational Astrophysics, Time Measurement

Scientific paper

Fifteen ROSAT PSPC observations available in the public archive are analyzed in order to study time and spectral variability of the 12 Einstein Extended Medium Sensitivity Survey (EMSS) AGN detected by ROSAT with more than 2000 net counts. Time variability was investigated on 13 different time-scales, ranging from 400 to 3.15 x 10 exp 6 s (1 yr). Of the 12 sources analyzed, only two do not show a significant variability on any time-scale. On a short time-scale, not more than 20 percent of AGN are seen as variable sources, while on a time-scale of not less than 100,000 s the fraction becomes not less than 50 percent. However, the visibility function for variability is far from being uniform, and small amplitude variations can be detected more often on a long time-scale than on a short time-scale. Spectral variability was detected in only two sources: MS1158.6-0323 shows a hardening of the spectrum with increasing intensity, while MS2254.9-3712 shows a softening of the spectrum with increasing intensity. Finally, for one source (MS1416.3-1257), the observed variability is the result not of an intrinsic flux variation but of a variation in the column density along the line of sight.

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