A comparison of X-ray photon indices among the narrow and broad-line
  Seyfert 1 galaxies
  We present a detailed comparative systematic study using a sample of 221
Narrow-line Seyfert 1 (NLSy1) galaxies in comparison to a redshift matched
sample of 154 Broad-line Seyfert 1 (BLSy1) galaxies based on their observations
using ROSAT and/or XMM-Newton telescopes in soft X-ray band (0.1-2.0 keV). A
homogeneous analysis is carried out to estimate their soft X-ray photon indices
($\Gamma^{s}_{X}$) and its correlations with other parameters of nuclear
activities such as Eddington ratios (R$_\mathrm{Edd}$), bolometric luminosities
(L$_\mathrm{bol}$), black hole masses (M$_\mathrm{BH}$) and the widths of the
broad component of H$\beta$ lines (FWHM(H$\beta$)). In our analysis, we found
clear evidence of the difference in the $\Gamma^{s}_{X}$ and R$_\mathrm{Edd}$
distributions among NLSy1 and BLSy1 galaxies, with steeper $\Gamma^{s}_{X}$ and
higher R$_\mathrm{Edd}$ for the former. Such a difference also exists in the
spectral indices distribution in hard X-ray ($\Gamma^{h}_{X}$), based on the
analysis of 53 NLSy1 and 46 BLSy1 galaxies in the 2-10 keV energy band. The
difference in R$_\mathrm{Edd}$ distributions does exist even after applying the
average correction for the difference in the inclination angle of NLSy1 and
BLSy1 galaxies. We also estimated R$_\mathrm{Edd}$, based on SED fitting of 34
NLSy1 and 30 BLSy1 galaxies over the 0.3-10 keV energy band and found that
results are still consistent with R$_\mathrm{Edd}$ estimates based on the
optical bolometric luminosity. Our analysis suggests that the higher
R$_\mathrm{Edd}$ in NLSy1 is responsible for its steeper X-ray spectral slope
compared to the BLSy1, consistent with the disc-corona model as proposed for
the luminous AGNs.
