Advantages of spectrum-röntgen-gamma and INTEGRAL for the study of narrow-line seyfert 1 galaxies

This paper summarizes the spectral and timing properties of narrow-line Seyfert 1 galaxies (NLS1) in view of recent ROSAT and ASCA observations. NLS1 have generally steeper soft (0.1-2.4 keV) X-ray continuum slopes than Seyfert 1s with broader lines, and there exists an anticorrelation between the 0.1-2.4 keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1-2.4 keV continuum slopes and Hβ FWHM > 3000 km s^-1 are clearly discriminated against by nature. When simple power-law models are fit to ROSAT spectra, photon indices reach values up to about 5, much higher than is usually seen in Seyfert 1s. Interestingly, the hard (2-10 keV) X-ray continuum slopes tend also to be steeper in NLS1 compared to broad-lined Seyfert 1 galaxies. We also report evidence for giant and rapid soft X-ray variability in the narrow-line Seyfert 1 galaxy IRAS 13224-3809 and the narrow-line quasar PHL 1092. The advantages of Spectrum-Röntgen-Gamma (SRG) and INTEGRAL for the study of NLS1 are discussed.