Discovery of an ultrasoft transient ROSAT AGN: WPVS 007.
de Martino, D.; Grupe, D.; Mannheim, K.; Thomas, H. -C.; Fink, H. H.; Beuerman, K.
Abstract
We have identified the ROSAT source RX J0039.2-5117 with the previously almost unknown 'narrow line' Seyfert 1 galaxy WPVS007 (z = 0.028). The X-ray source displays quite unusual properties for an AGN. It was bright and ultrasoft in the ROSAT All-Sky Survey (RASS) and found at a level lower by a factor of ~400 in PSPC count rate in 1993. The implied 0.1-2.4 keV luminosity during the RASS was ~10^37^W. We discuss possible explanations for the extremely soft X-ray spectrum and the observed variability.