AAS Meeting #193 - Austin, Texas, January 1999
Session 90. Ultra-Luminous IR Galaxies/AGN - The Central Regions
Oral, Friday, January 8, 1999, 2:00-3:30pm, Room 8 (A,B,C)

## [90.05] ASCA Observations of the Extreme Narrow-Line Seyfert 1 Galaxies Mrk 42 and Mrk 957

S. A. Snedden, C. M. Gaskell (U. Nebraska), W. N. Brandt (Penn. State U.), C. Otani (RIKEN)

Narrow-Line Seyfert 1 galaxies (NLS1s) represent an extreme of a wide range of correlated spectral properties of AGNs (the so-called Boroson & Green eigenvector 1''). Optically NLS1 show narrow broad'' lines and weak Balmer emission, but strong Fe II emission. Mrk 42 and Mrk 957 are two of the most optically extreme NLS1s in that they have extremely narrow broad lines and a very low H\beta equivalent width. We have observed these two NLS1s with ASCA and carried out simultaneous optical monitoring. We discuss the ASCA spectra and the relationship of the X-ray spectral properties of these extreme objects to properties in other spectral regions. We make a comparison with more normal (i.e., non-NLS1) AGNs and discuss possible explanations for the extreme properties of NLS1s.