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K. M. Leighly, D. A. Casebeer (The University of Oklahoma), F. Hamann (University of Florida), D. Grupe (Pennsylvania State University)
We report emergence of a broad absorption-line (BAL) flow in the peculiar narrow-line Seyfert 1 Galaxy WPVS 007 (z=0.0288). WPVS 007 was observed to have normal X-ray luminosity in the ROSAT All Sky Survey, but in subsequent X-ray observations from 1993 to 2002, it nearly disappeared from the X-ray sky. Most NLS1s are bright soft X-ray sources, and the origin of this X-ray weakness was unknown until now. Observed to have a miniBAL with maximum velocity vmax ~1000\, \rm km\, s-1 in an HST observation from 1996, it was discovered to have developed an additional BAL flow by the time of the FUSE observation seven years later. The BAL flow has a maximum velocity of ~6,000 \rm \, km\,s-1, and the unambiguous presence of \ion{P}{5} indicates that it is very optically thick. BALQSOs are notoriously X-ray weak and X-ray spectroscopy from other BALQSOs indicates that this is because they are absorbed. Thus, the change in X-ray flux is plausibly a result of absorption due to the development of the BAL flow.
Variability in broad absorption lines are generally confined to changes in optical depth, and the emergence of a BAL flow has never been observed before. Furthermore, the observation of a BAL flow in an object with such low luminosity (MV=-19.7) is unprecedented. However, these two properties may be connected. WPVS~007 has a small black hole mass (1.2 \times 106 M\odot based on the Kaspi relationship) so size scales are small and time scales are short. Similar changes on a 7-year time scale might be impossible in a more typical BAL quasar which may be 1000 times more luminous with correspondingly larger emission regions and longer time scales.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.