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Astron. Astrophys. 350, 816-826 (1999)


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The steep spectrum quasar PG1404+226 with ASCA, HST and ROSAT

M.-H. Ulrich 1, A. Comastri 2, S. Komossa 3 and P. Crane 1,4

1 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
2 Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
3 Max-Planck-Institute für Extraterrestrische Physik, Giessenbach Strasse, 85748 Garching, Germany
4 Department of Physics and Astronomy, Wilder Laboratory, Dartmouth College, Hanover N.H. 03755, USA

Received 19 April 1999 / Accepted 5 July 1999

Abstract

We present and discuss our observations of the Narrow Line quasar PG1404+226 ([FORMULA] = 0.098) with ASCA and HST, and a re-analysis of our earlier observations with ROSAT. The soft X-ray spectrum is very steep and displays an absorption feature (edge or line at [FORMULA] 1.1 keV). We have applied a variety of models to the ASCA and ROSAT spectra without finding a completely satisfactory fit, and the identification of the edge remains uncertain. A satisfactory fit of the ASCA spectrum assuming that the edge is produced by highly ionized iron (using the code absori in XSPEC) is obtained with an overabundance of iron by a factor [FORMULA] compared to solar, a suggestion supported by the extremely high equivalent width of the Fe K[FORMULA] line at 6.4 keV. A warm absorber model (based on Cloudy) fitting the absorption feature with NeVII-NeX edges and assuming a peculiar oxygen/neon abundance ratio is consistent with the ROSAT data but not the ASCA data. Finally, it is also possible that the observed edge is caused by a OVIII or OVII edge or line, blueshifted by [FORMULA] = 0.2 to 0.5 depending on the specific identification, as has been suggested previously for 2 other Narrow Line quasars, but there are no other features in the UV and X-ray spectra in support of this suggestion.

Two systems of UV absorption lines, one nearly at rest in the source frame, the other blueshifted by [FORMULA] km s-1 are identified in the HST/FOS spectra. Photoionization models indicate that the UV absorption and the [FORMULA] keV absorption are probably caused by absorbers with different physical conditions. PG1404+226 is one more case of AGN where both UV and X-ray absorption features are detected, thereby increasing further the significance of the previously noted statistical association of the two types of absorbers.

Key words: galaxies: active – galaxies: quasars: individual: PG 1404+226 – galaxies: spiral – ultraviolet: galaxies – X-rays: galaxies

Send offprint requests to: M.-H. Ulrich

© European Southern Observatory (ESO) 1999

Online publication: October 14, 1999

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