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Session 98 - AGN-Absorption/Emission.
Display session, Thursday, January 16
We study the far-UV spectra of the Seyfert 1 galaxy Mrk 478 and the quasar PG1211+143 obtained with the Hopkins Ultraviolet Telescope (\hut) between 912 and 1840 Åalong with the archival HST FOS spectra. Both objects are known for their narrow emission-line widths and their exceptionally strong soft X-ray excess. Major emission lines can be fitted with a narrow component of FWHM \sim 2000 \kms\ and a broad one with FWHM \sim 8000 \kms. Broad C \sc iii \lm 977 and N \sc iii \lm 991 emission is clearly visible in both objects. Their intensities relative to their respective counterparts at \lm 1909 and \lm 1750 indicate high temperature in the line-forming region, on the order of 50,000 K. The intensity of the broad He \sc ii \lm 1640 emission is \sim 10% of that of the broad \lya\ emission, and the øvi\ \lm 1034 intensity is close to the \civ\ \lm 1549 intensity for both the narrow and broad components. The relative intensities of \he\ and øvi\ emission in these two objects are among the highest observed in any AGN. We suggest that a high flux of ionizing photons in the extreme UV and soft X-ray band enhances the intensities of high-ionization emission lines, and these high-ionization lines may be useful to constrain the continuum shape between \sim 50 and 100 eV.
Program listing for Thursday