Black hole masses in NLS1 galaxies from the X-ray excess variance method

Abstract

We estimate black hole masses in Narrow Line Seyfert 1 (NLS1) galaxies at the basis of their X-ray excess variance. We apply the standard approach appropriate for Broad Line Seyfert 1 (BLS1) galaxies. In general, we find that the obtained masses are by a factor \sim 20 too small to agree with values obtained from other methods (reverberation, stellar dispersion). However, a small subset of our NLS1 objects does not require that multiplication, or the correction factor is less than 4. We find that this subset have a soft X-ray photon index, \Gamma_{0.1-2.4 keV}, smaller than 2. We thus postulate that this subclass of NLS1 actually belongs to BLS1.