An Update on the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: Swift observations of UV variability and persistence of X-ray faintness

Abstract

We report on the detection of UV variability and the persistence of X-ray faintness of the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007 based on the first year of monitoring this AGN with Swift between 2005 October and 2007 January. WPVS 007 has been an unusual source. While being X-ray bright during the ROSAT All-Sky Survey it has been extremely faint in all following X-ray observations. Swift also finds this NLS1 to be X-ray faint and not detected in the Swift X-Ray Telescope at an 3$\sigma$ upper limit of $2.6\times 10^{-17}$ W m${}^{-2}$ in the 0.3-10.0 keV band and confirms that the AGN is still in a low state. During the 2006 July and December observations with \swift's UV-Optical Telescope (UVOT) the AGN became fainter by about 0.2 mag in the UV filters and by about 0.1 mag in V, B, and U compared with the 2005 October to 2006 January and 2006 September/October observations followed by a rebrightening in the 2007 January observation. This variability can be caused either by a change in the absorption column density and therefore the reddening in the UV, or by flux variations of the central engine. We also noticed that the flux in the UVOT filters agree with earlier measurements by the International Ultraviolet Explorer taken between 1993-1995, but spectra taken by the Hubble Space Telescope Faint Object Spectrograph show that WPVS 007 was fainter in the UV by a factor of at least 2 in 1996. The flat optical/UV spectrum suggests that some UV extinction is present in the spectrum, but that alone cannot at all account for the dramatic fading in the X-ray flux. Most likely we see a partial covering absorber in X-rays. Alternatively, the current X-ray emission seen from WPVS 007 may also be the emission from the host galaxy.

arXiv commentAccepted for publications in the Astronomical Journal, 14 pages, 5 figures, 4 tables

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• Variable Reddening and Broad Absorption Lines in the Narrow-line Seyfert 1 Galaxy WPVS 007: an Origin in the Torus
• Studying X-ray reprocessing and continuum variability in quasars: PG 1211+143
• A long hard look at the minimum state of PG 2112+059 with XMM-Newton
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• Investigating the {Origin} of the Absorption-Line Variability in Narrow-Line Seyfert 1 Galaxy WPVS 007
• Transient X-ray Emission from Normal Galactic Nuclei
• Is there a connection between Broad Absorption Line Quasars and Narrow Line Seyfert 1 galaxies?
• On the Origin of the Dramatic Spectral Variability of WPVS 007