Volume 490, Number 3, November II 2008
|Page(s)||995 - 1003|
|Published online||18 September 2008|
The X-ray variability and the near-IR to X-ray spectral energy distribution of four low luminosity Seyfert 1 galaxies
Physics Department, University of Crete, PO Box 2208, 710 03 Heraklion, Crete, Greece e-mail: firstname.lastname@example.org
2 IESL, Foundation for Research and Technology, 711 10 Heraklion, Crete, Greece
3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany
4 Institute of Astronomy and Astrophysics, National Observatory of Athens, I. Metaxa & V. Pavlou, 152 36 P. Penteli, Athens, Greece
Accepted: 26 August 2008
Context. We present the results from a study of the X-ray variability and the near-IR to X-ray spectral energy distribution of four low-luminosity, Seyfert 1 galaxies.
Aims. We compared their variability amplitude and broad band spectrum with those of more luminous AGN in order to investigate whether accretion in low-luminosity AGN operates as in their luminous counterparts.
Methods. We used archival XMM-Newton and, in two cases, ASCA data to estimate their X-ray variability amplitude and determine their X-ray spectral shape and luminosity. We also used archival HST data to measure their optical nuclear luminosity, and near-IR measurements from the literature, in order to construct their near-IR to X-ray spectra.
Results. The X-ray variability amplitude of the four Seyferts is what one would expect, given their black hole masses. Their near-IR to X-ray spectrum has the same shape as the spectrum of quasars that are 102–105 times more luminous.
Conclusions. The objects in our sample are optically classified as Seyfert 1–1.5. This implies that they host a relatively unobscured AGN-like nucleus. They are also of low luminosity and accrete at a low rate. They are therefore good candidates to detect radiation from an inefficient accretion process. However, our results suggest that they are similar to AGN that are 102–105 times more luminous. The combination of a “radiative efficient accretion disc plus an X-ray producing hot corona” may persist at low accretion rates as well.
Key words: galaxies: active / galaxies: Seyfert / X-rays: galaxies
© ESO, 2008
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