We present a study of the soft X-ray properties of a sample of 15 Seyfert 1 observed with ASCA. The spectrum of 11 objects in the sample shows a soft excess over a single power-law model. We found that the best interpretation of this excess is a thermal radiation coming from the innermost region of an accretion disc. Indeed the use of a black body model gives a good fit in 9 sources out of the 11 that show the excess. However the temperatures obtained from the best fit are higher than those expected if the emission comes from a region just outside the last stable orbit around a non-rotating black hole (Schwarzschild black hole). The temperatures obtained seem to indicate that the emission region is closer than three Schwarzschild radii, suggesting the presence of a Kerr (rotating) black hole.
Implication of the thermal origin of the soft excess in Seyfert 1 galaxies
BURDERI, LUCIANO;
1999-01-01
Abstract
We present a study of the soft X-ray properties of a sample of 15 Seyfert 1 observed with ASCA. The spectrum of 11 objects in the sample shows a soft excess over a single power-law model. We found that the best interpretation of this excess is a thermal radiation coming from the innermost region of an accretion disc. Indeed the use of a black body model gives a good fit in 9 sources out of the 11 that show the excess. However the temperatures obtained from the best fit are higher than those expected if the emission comes from a region just outside the last stable orbit around a non-rotating black hole (Schwarzschild black hole). The temperatures obtained seem to indicate that the emission region is closer than three Schwarzschild radii, suggesting the presence of a Kerr (rotating) black hole.
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