Far - Ultraviolet Observations of NGC 3516 using the Hopkins UltravioletTelescopeG

We observed the Seyfert 1 galaxy NGC 3516 twice during the ight 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 A with a resolution of 2{4 A. No signiicant variations were found between the two observations. The total spectrum shows a red continuum, f ?1:89 , with an observed ux of 2:2 10 ?14 erg cm ?2 s ?1 A ?1 at 1450 A, slightly above the historical mean. Intrinsic absorption in Lyman is visible as well 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 400 km s ?1 relative to the systemic velocity, and it is opaque at the Lyman limit. The sharpness of the cutoo indicates a low eeective Doppler parameter, b < 20 km s ?1. For b = 10 km s ?1 the derived intrinsic column is 3:5 10 17 cm ?2. 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 10 3 in both ionization parameter and column density.