Physics
Scientific paper
Jun 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aspc..311..261w&link_type=abstract
AGN Physics with the Sloan Digital Sky Survey, Proceedings of a conference held in Princeton, NJ, USA, 27-31 July 2003, Edited b
Physics
Scientific paper
Many consider ultrasoft X-ray emission to be a defining characteristic of narrow-line Seyfert 1 galaxies (NLS1s); indeed, many known NLS1s have been selected on this basis. In our sample of 150 optically-selected NLS1s from the Sloan Digital Sky Survey Early Data Release, 52 were associated with X-ray sources detected in the ROSAT All-Sky Survey. Most of the objects not detected by ROSAT are optically faint, but a subset of them exhibit optical characteristics similar to the X-ray detected NLS1s, and so should have been detected themselves. We have observed eleven of these ROSAT-undetected NLS1s with Chandra ACIS-S for 2 ksec each. Eight of these objects appear to exhibit normal NLS1 X-ray properties, but three are uncharacteristically faint and may have very flat X-ray spectra. While the bright objects in our Chandra sample may be highly variable and thus were in a low-luminosity state when observed with ROSAT, the other three cannot be easily explained without invoking high intrinsic neutral column densities or other phenomena previously unobserved in NLS1s.
Mathur Savita
Pogge Richard
Williams Richard
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