PG 0946+301: the Rosetta Stone of BALQSOs?

We describe the motivation and features of a multiwavelength spectroscopic campaign on broad absorption line (BAL) QSO PG~0946+301. The main goal of this project is to determine the ionization equilibrium and abundances (IEA) in BAL outflows. Previous studies of IEA in BALQSOs were based on the assumption that the BALs are not saturated so that the column densities inferred from the apparent optical depths are realistic. This critical assumption is at odds with several recent observations and with analysis of existing data which indicate that the absorption troughs are heavily saturated even when they are not black. In addition, X-ray observations, which are important for constraining the ionizing continuum, were not available for those objects that had UV spectral data. Quantifying the level of saturation in the BALs necessitates UV spectroscopy with much higher S/N and broader spectral coverage than currently exist. After taking into account the capabilities of available observatories, our best hope for a substantial improvement in understanding the IEA in BALQSOs is to concentrate considerable observational resources on the most promising object. Our studies of available HST and ground-based spectra show that PG~0946+301 is by far the best candidate for such a program. This BALQSO is at least five times brighter, shortward of 1000 A rest frame, than any other object, and due to its low redshift it has an especially sparse Lya forest. At the same time PG~0946+301 is a typical BALQSO and therefore its IEA should be representative. To this effect we are developing a multiwavelength spectroscopic campaign (UV, FUV, X-ray and optical) on BALQSO PG 0946+301. We discuss the goals and feasibility of each observational component: HST, FUSE, ASCA and ground-based.Comment: 7 pages including 2 figures. To be published in the proceednigs of the: "Structure and Kinematics of Quasar Broad Line Regions" conference, ed. C. M. Gaskell, W. N. Brandt, M. Dietrich, D. Dultzin-Hacyan, and M. Eracleou

What is the redshift of gamma-ray burst 970508?

A Bayesian likelihood analysis is used to constrain the redshift of the optical transient associated with gamma-ray burst 970508, under the assumption that the absorption at redshift 0.835 is not physically associated with the transient. The maximum-likelihood, expectation value and 95-percent upper limit on the OT redshift are 0.835, 1.3 and 1.9 respectively.Comment: 6 pages, including 2 figures, submitted to ApJ Letter

On the Column Density of AGN Outflows: the Case of NGC 5548

We re-analyze the HST high resolution spectroscopic data of the intrinsic absorber in NGC 5548 and find that the C IV absorption column density is at least four times larger than previously determined. This increase arises from accounting for the kinematical nature of the absorber and from our conclusion that the outflow does not cover the narrow emission line region in this object. The improved column density determination begins to bridge the gap between the high column densities measured in the X-ray and the low ones previously inferred from the UV lines. Combined with our findings for outflows in high luminosity quasars these results suggest that traditional techniques for measuring column densities: equivalent width, curve-of-growth and Gaussian modeling, are of limited value when applied to absorption associated with AGN outflows.Comment: Published ApJ version (566, 699), including a new figure with FUSE data and a useful algebraic expression for the optical depth solutio