Far-Ultraviolet Observations of NGC 3516
using the Hopkins Ultraviolet Telescope

G. A. Kriss, B. R. Espey, J. H. Krolik, Z. Tsvetanov,
W. Zheng, and A. F. Davidsen
Department of Physics & Astronomy,
Johns Hopkins University,
Baltimore, MD 21218

Abstract:

We observed the Seyfert 1 galaxy NGC 3516 twice during the flight of Astro-2 using the Hopkins Ultraviolet Telescope aboard the space shuttle Endeavour in March 1995. Simultaneous X-ray observations were performed with ASCA. Our far-ultraviolet spectra cover the spectral range 820--1840 Å with a resolution of 2--4 Å. No significant variations were found between the two observations. The total spectrum shows a red continuum, , with an observed flux of at 1450 Å, slightly above the historical mean. Intrinsic absorption in Lyman is visible as well as absorption from O VI , N V , Si IV , and C IV . The UV absorption lines are far weaker than is usual for NGC 3516, and also lie closer to the emission line redshift rather than showing the blueshift typical of these lines when they are strong. The neutral hydrogen absorption, however, is blueshifted by relative to the systemic velocity, and it is opaque at the Lyman limit. The sharpness of the cutoff indicates a low effective Doppler parameter, . For the derived intrinsic column is . As in NGC 4151, a single warm absorber cannot produce the strong absorption visible over the wide range of observed ionization states. Matching both the UV and X-ray absorption simultaneously requires absorbers spanning a range of in both ionization parameter and column density.

Subject headings: galaxies: active --- galaxies: individual (NGC 3516) --- galaxies: nuclei --- galaxies: Seyfert --- ultraviolet: galaxies



gak@pha.jhu.edu