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Astron. Astrophys. 349, 88-96 (1999)


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X-ray properties of LINERs

Stefanie Komossa 1, Hans Böhringer 1 and John P. Huchra 2

1 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-20, Cambridge, MA 02138, USA

Received 6 April 1999 / Accepted 17 June 1999

Abstract

We present an investigation of the X-ray properties of 13 LINERs based on ROSAT all-sky survey and pointed PSPC and HRI observations. Several sources are studied for the first time in X-rays. The X-ray spectra are best described by a powerlaw with photon index [FORMULA] [FORMULA] -2.0 or thermal emission from gas with very subsolar abundances. The luminosities range between [FORMULA] (NGC 404) and 40.8 (NGC 4450). No X-ray variability on the timescale of hours/days is detected. This is in line with the suggestion that LINERs may accrete in the advection-dominated mode. On a longer term, one of the objects, NGC 2768, turns out to be slightly variable. Some sources appear to be extended at weak emission levels whereas the bulk of the X-ray emission is consistent with arising from a point source within the PSPC instrumental resolution. [FORMULA]/[FORMULA] ratios are derived and emission mechanisms that potentially contribute to the observed X-ray luminosities are discussed.

We also examine the presence of second X-ray sources near the target sources both in terms of instrumental effects and in terms of `real' sources within the LINER galaxies.

Key words: galaxies: active – galaxies: fundamental parameters – galaxies: ISM – galaxies: nuclei – X-rays: galaxies

Send offprint requests to: St. Komossa (skomossa@xray.mpe.mpg.de)

© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999

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