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G. A. Shields (U. Texas Austin)
PG 1222+228 is one of several QSOs that show an abrupt, strong rise in polarization at a rest wavelength of about 750 A. The origin of this polarization rise is unknown, but it may provide an important diagnostic for AGN accretion disks. In the case of PG 1222+228, the polarization rise concides in wavelength with a sharp drop in flux. The possibility that the polarization rise in this object is caused by a high velocity outflow, analagous to the situation in some broad absorption line QSOs, is examined and found to be unpromising. The data are consistent with the idea that the absorption feature is an intervening Lyman limit system (LLS) that happens to fall at the wavelength of an intrinsic polarization rise in the QSO spectrum. When corrected for the LLS absorption, the polarized flux of PG 1222+228 rises strongly at the wavelength of the polarization rise. This resembles the case of PG 1630+377, and it puts especially stringent requirements on theoretical models for the polarization rise. PG 1222+228 may be an example of a polarization rise QSO whose intrinsic energy distribution does not show a steep drop in the Lyman continuum.
This work was supported in part by the Space Telescope Science Institute under grant GO-07359.02-96A.
The author(s) of this abstract have provided an email address for comments about the abstract: shields@astro.as.utexas.edu