Far-ultraviolet observations of NGC 3516 using the Hopkins ultraviolet telescope
Item Type:Journal Article
Citation:Kriss, G. A.; Espey, B. R.; Krolik, J. H.; Tsvetanov, Z.; Zheng, W.; Davidsen, A. F. 'Far-ultraviolet observations of NGC 3516 using the Hopkins ultraviolet telescope' in Astrophysical Journal, 467, 1996, pp. 622-628.
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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 the Advanced Satellite for Cosmology and Astrophysics. Our far- ultraviolet spectra cover the spectral range 820-1840 A, with a resolution of 2-4 A. No significant variations were found between the two observations. The total spectrum shows a red continuum, fnu_ ~ ?^- 1.89^, with an observed flux of 2.2 x 10^-14^ ergs cm^-2^ s^-1^ A^-1^ at 1450 A, slightly above the historical mean. Intrinsic absorption in Ly?_ is visible as well as absorption from O VI ??1032, 1038, N V ??1239, 1243, Si IV ??1394,1403, and C IV ??1548,1551. 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 cutoff indicates a low effective Doppler parameter, b < 20 km s^-1^. For b = 10 km s^-1^, the derived intrinsic column density is 3.5 x 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.
Author: ESPEY, BRIAN RUSSELL
Publisher:American Astronomical Society
Type of material:Journal Article
Availability:Full text available