X-ray and optical spectroscopy of IRAS 20181{minus}2244: Not a type 2 QSO, but A I Zw 1 object
We analyze new optical spectra of IRAS 20181{minus}2244 that confirm its classification as a I Zw 1 object (or narrow-line Seyfert 1 galaxy), one of 20 such objects detected in the {ital ROSAT/IRAS} all-sky survey. {ital ASCA} X-ray data on IRAS 20181{minus}2244 support this classification since they are fitted by a simple power-law spectrum of {Gamma}=2.37{plus_minus}0.09 that 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 IRAS 20181{minus}2244, ruling out a hidden/scattered QSO interpretation for this object. Its 0.5{endash}10 keV luminosity is 5.5{times}10{sup 44}ergss{sup {minus}1}, and its variability signifies an efficiency of at least 4{percent} for conversion of gravitational energy to X-rays. We discuss the important differences between the I Zw 1 class and the {open_quotes}type 2 QSO,{close_quotes} or high-luminosity Seyfert 2 galaxy. While I Zw 1 objects of QSO-like luminosity are ubiquitous 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 one in X-rays. It is not clear how this imbalance relates to unified models of AGNs. {copyright} {ital 1998} {ital The American Astronomical Society}
- Research Organization:
- Lawrence Livermore National Laboratory
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 625369
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 494; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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