Abstract
This paper summarizes the spectral and timing properties of narrow-line Seyfert1 galaxies (NLS1) in view of recent ROSAT and ASCA observations. NLS1have 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 0.1–2.4keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1–2.4keV 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 inSeyfert 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 reportevidence for giant and rapid soft x-ray variability in the narrow-line Seyfert1 galaxy IRAS 13224–3809 and the narrow-line quasar PHL 1092. The advantagesof Spectrum-Röntgen-Gamma (SRG) and INTEGRAL for the study ofNLS1 are discussed.
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