[Previous] | [Session 23] | [Next]
W.N. Brandt, S.C. Gallagher, R.M. Sambruna (Penn State), S. Mathur (Harvard CfA), N. Yamasaki (Tokyo Metropolitan)
We present the analysis and interpretation of a sample of nine ASCA/SAX observations of Broad Absorption Line Quasi-Stellar Objects (BALQSOs). This is the first moderate-size sample of sensitive BALQSO observations from 2--10~keV, and the BALQSOs in our sample are among the optically brightest known. Despite the ability of 2--10~keV X-rays to penetrate large column densities, we find that in general BALQSOs are surprisingly weak sources above 2~keV. By comparison with non-BALQSOs of similar optical continuum magnitudes, we derive the column densities needed to suppress the expected X-ray fluxes of our BALQSOs. In several cases we derive column densities >5\times 1023~cm-2 for a neutral absorber with solar abundances. These are the largest X-ray column densities yet inferred for BALQSOs, and they exceed ROSAT lower limits by about an order of magnitude. If the same outflowing gas makes both the X-ray and ultraviolet absorption, our column density limits raise the implied mass outflow rate and kinetic luminosity by about an order of magnitude. We discuss the physical plausibility and general implications of such powerful outflows from BALQSOs.
Optical brightness does not appear to be a good predictor of 2--10~keV brightness for BALQSOs, but our data do suggest that the BALQSOs with high optical continuum polarizations may be the X-ray brighter members of the class. We discuss physical models for the nuclear geometry that could lead to a connection between polarization and X-ray flux. Finally, we discuss the implications of our results for future observations with AXAF and XMM.
If the author provided an email address or URL for general inquiries,
it is as follows: