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For refcode 1993ApJ...416..536S:
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1993ApJ...416..536S VARIABLE C IV ABSORPTION IN THE SEYFERT GALAXY NGC 5548: A CONNECTION TO BROAD ABSORPTION LINE QUASI-STELLAR OBJECTS? J. MICHAEL SHULL AND ELISE R. SACHS Center for Astrophysics and Space Astronomy, Department of Astrophysical, Planetary, and Atmospheric Sciences, University of Colorado, Campus Box 389, Boulder, CO 80309 Received 1993 January 4; accepted 1993 April 13 ABSTRACT This is the second in a series of papers examining variable absorption components in the broad emission lines of Seyfert 1 galaxies. In an IUE survey of a complete sample of CfA Seyfert galaxies, we find that at least 12% and perhaps as many as 27% of the objects show evidence of intrinsic absorption in C IV {lambda}1549. In this paper, we use data from an 8 month IUE campaign on NGC 5548 to study the C IV absorption component. From the observed fluxes and C IV ionization conditions, we infer that the C IV absorption occurs within (14 pc)r_6_^-1/2^ of the nucleus. The C IV absorption feature is blueshifted by ~1200 km s^-1^ from the systemic velocity of the galaxy and varies on a timescale of 4 days or less, indicating that n_e_ >= 5 x 10^5^ cm^-3^ from recombination-response arguments. The C IV absorption equivalent width strongly anticorrelates with continuum flux at 1570 A. The broad-line region must be at least partially covered by the absorbing region, and the central wavelength of the broad-line region corresponds to that of the maximum absorption. Standard broad-line clouds cannot account for the absorption feature, and the absorbing material must be optically thin and dispersed in velocity space. We propose a relationship between broad absorption line (BAL) QSOs and Seyfert 1 galaxies with absorption, and we suggest that the latter may be a low- luminosity, low-redshift manifestation of the BAL phenomenon in quasars. The high frequency of occurrence may represent a statistical effect of outflow viewing angle on the sky. Subject headings: galaxies: Seyfert - galaxies: individual (NGC 5548) - quasars: general - ultraviolet: galaxies
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