1ES 1927+654: Persistent and rapid X-ray variability in an AGN with low intrinsic neutral X-ray absorption and narrow optical emission lines

We present X-ray and optical observations of the X-ray bright AGN 1ES 1927+654. The X-ray observations obtained with ROSAT   and Chandra reveal persistent, rapid and large scale variations, as well as steep 0.1–2.4 keV ($\rm \Gamma = 2.6 \pm 0.3$) and 0.3–7.0 keV ($\rm \Gamma = 2.7 \pm 0.2$) spectra...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2003-01, Vol.397 (2), p.557-564
Main Authors: Boller, Th, Voges, W., Dennefeld, M., Lehmann, I., Predehl, P., Burwitz, V., Perlman, E., Gallo, L., Papadakis, I. E., Anderson, S.
Format: Article
Language:English
Subjects:
Astrophysics
Cosmology and Extra-Galactic Astrophysics
galaxies: active
galaxies: individual: 1ES 1927+654
galaxies: Seyfert
Physics
X-rays: galaxies
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Summary:We present X-ray and optical observations of the X-ray bright AGN 1ES 1927+654. The X-ray observations obtained with ROSAT   and Chandra reveal persistent, rapid and large scale variations, as well as steep 0.1–2.4 keV ($\rm \Gamma = 2.6 \pm 0.3$) and 0.3–7.0 keV ($\rm \Gamma = 2.7 \pm 0.2$) spectra. The measured intrinsic neutral X-ray column density is approximately $\rm 7 \times 10^{20}\ cm^{-2}$. The X-ray timing properties indicate that the strong variations originate from a region, a few hundred light seconds from the central black hole, typical for type 1 AGN.
High quality optical spectroscopy reveals a typical Seyfert 2 spectrum with some host galaxy contamination and no evidence of Fe II multiplets or broad hydrogen Balmer wings. The intrinsic optical extinction derived from the BLR and NLR are $A_V \ge 3.7$ and AV=1.7, respectively. The X-ray observations give an AV value of less than 0.58, in contrast to the optical extinction values.
We discuss several ideas to explain this apparent difference in classification including partial covering, an underluminous BLR or a high dust to gas ratio.
ISSN:0004-6361
1432-0746
1432-0756
DOI:10.1051/0004-6361:20021520