The unusual X-ray and optical properties of the ultrasoft active galactic nucleus Zwicky 159.034 (RE J1237+264)

Zwicky 159.034, one of the Seyfert galaxies identified with extreme-ultraviolet (EUV) sources detected during the ROSAT Wide Field Camera (WFC) all-sky survey, has unusual properties. The ROSAT Position Sensitive Proportional Counter (PSPC) 0.1-2.5 keV X-ray spectrum, obtained simultaneously with the WFC survey, appears extremely steep. Subsequent deeper pointed observations with ROSAT revealed that its 0.1-2.5 keV count rate had decreased by an extremely large amount (a factor of ~70). This is comparable to the variability amplitude seen in another ultrasoft Seyfert, E1615+061. There appears to be ~10 times as much flux in the soft component as in any expected hard tail, suggesting that, in the absence of partial covering of the hard flux, the soft flux cannot arise via reprocessing of the hard tail. Zwicky 159.034's peculiar optical spectrum has permitted lines with widths ~1200-1500 km s^-1, and forbidden lines are weak or absent. Its optical spectrum shows evidence for variability, and might be used to study the role that reprocessed X-rays play in the formation of optical lines.