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

Abstract

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