Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aas...189.9813z&link_type=abstract
American Astronomical Society, 189th AAS Meeting, #98.13; Bulletin of the American Astronomical Society, Vol. 28, p.1406
Astronomy and Astrophysics
Astronomy
1
Scientific paper
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 Angstroms, along 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 ~ 2000 \kms\ and a broad one with FWHM ~ 8000 \kms. Broad C iii \lm 977 and N 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 ii \lm 1640 emission is ~ 10% of that of the broad \lya\ emission, and the \ovi\ \lm 1034 intensity is close to the \civ\ \lm 1549 intensity for both the narrow and broad components. The relative intensities of \he\ and \ovi\ 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 ~ 50 and 100 eV.
Davidsen Arthur F.
Kriss Gerard Anthony
Zheng Wei
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