Emergence of a Broad Absorption Line Outflow in the Narrow-line Seyfert 1 Galaxy WPVS 007

We report results from a 2003 Far Ultraviolet Spectroscopic Explorer (FUSE) observation and reanalysis of a 1996 Hubble Space Telescope (HST) observation of the unusual X-ray transient Narrow-line Seyfert 1 galaxy WPVS 007. The HST Faint Object Spectrograph (FOS) spectrum revealed mini-BALs (broad absorption lines) with V _max ~ 900 km s^-1 and FWHM ~550 km s^-1. The FUSE spectrum showed that an additional BAL outflow with V _max ~ 6000 km s^-1 and FWHM ~3400 km s^-1 had appeared. WPVS 007 is a low-luminosity object in which such a high-velocity outflow is not expected; therefore, it is an outlier on the M_V /v _max relationship. Template spectral fitting yielded apparent ionic columns, and a Cloudy analysis showed that the presence of P V requires a high-ionization parameter log(U) >= 0 and high-column density log(N _H) >= 23 assuming solar abundances and a nominal spectral energy distribution (SED) for low-luminosity NLS1s with α _ox = -1.28. A recent long Swift observation revealed the first hard X-ray detection and an intrinsic (unabsorbed) α _ox ≈ -1.9. Using this SED in our analysis yielded lower column density constraints (log(N _H) >= 22.2 for Z = 1, or log(N _H) >= 21.6 if Z = 5). The X-ray weak continuum, combined with X-ray absorption consistent with the UV lines, provides the best explanation for the observed Swift X-ray spectrum. The large column densities and velocities implied by the UV data in any of these scenarios could be problematic for radiative acceleration. We also point out that since the observed P V absorption can be explained by lower total column densities using an intrinsically X-ray weak spectrum, we might expect to find P V absorption preferentially more often (or stronger) in quasars that are intrinsically X-ray weak.

Based on observations made with the NASA-CNES-CSA Far-Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by Johns Hopkins University under NASA contract NAS5-32985.