VARIABLE-C-IV ABSORPTION IN THE SEYFERT-GALAXY NGC-5548 - A CONNECTION TO BROAD ABSORPTION-LINE QUASI-STELLAR OBJECTS

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 lambda1549. 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)r6(-1/2) of the nucleus. The C IV absorption feature is blueshifted by approximately 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) greater-than-or-equal-to 5 x 10(5) cm-3 from recombination-response arguments. The C IV absorption equivalent width strongly anticorrelates with continuum flux at 1570 angstrom. The broad-line region must be at least partially covered by the absorbing region, and the central wave-length 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.