ULTRASOFT NARROW-LINE SEYFERT-1 GALAXIES AND X-RAY SURVEYS

We describe how recent X-ray surveys have led to advances in the under standing of ultrasoft narrow-line Seyfert 1 galaxies. The number of kn own ultrasoft narrow-line Seyfert Is has increased greatly in recent y ears due to X-ray surveys, and it is now possible to obtain high quali ty 0.1-10 keV spectral and variability measurements for a large number of these galaxies. We generalize some of the correlations between X-r ay properties and optical emission line properties, focusing on how th e ROSAT band spectral slope appears to be directly connected to the Bo roson & Green (1992) primary eigenvector. We discuss how ultrasoft nar row-line Seyfert Is may well have extremal values of a primary physica l parameter, and we describe new projects that should further improve our understanding of these extreme representatives of Seyfert activity .