X-RAY AND OPTICAL SPECTROSCOPY OF IRAS-20181-2244 - NOT A TYPE-2 QSO BUT A-I ZW-1 OBJECT

We analyze new optical spectra of IRAS 20181 - 2244 that confirm its c lassification as a I Zw 1 object (or narrow-line Seyfert 1 galaxy), on e of 20 such objects detected in the ROSAT/IRAS all-sky survey. ASCA X -ray data on IRAS 20181 - 2244 support this classification since they are fitted by a simple power-law spectrum of Gamma = 2.37 +/- 0.09 tha t is typical of this class but steeper than that of ordinary Seyfert 1 or Seyfert 2 galaxies. Rapid X-ray variability is also observed in IR AS 20181 - 2244, ruling out a hidden/scattered QSO interpretation for this object. Its 0.5 - 10 keV luminosity is 5.5 x 10(44) ergs s(-1) an d its variability signifies an efficiency of at least 4 % for conversi on of gravitational energy to X-rays. We discuss the important differe nces between the I Zw 1 class and the ''type 2 QSO,'' or high-luminosi ty Seyfert 2 galaxy. While I Zw 1 objects of QSO-like luminosity are u biquitous in infrared, optical, and soft X-ray selected samples, type 2 QSOs are rare, and there is a dearth of evidence for even a single o ne in X-rays. It is not clear how this imbalance relates to unified mo dels of AGNs.