Far-ultraviolet observations of NGC 3516 using the Hopkins Ultraviolet Telescope

G. A. Kriss, B. R. Espey, J. H. Krolik, Zlatan Tsvetanov, W. Zheng, A. F. Davidsen

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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 the Advanced Satellite for Cosmology and Astrophysics. 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, fv ∼ v-1.89, with an observed flux of 2.2 × 10-14 ergs cm-2 s-1 Å-1 at 1450 Å, slightly above the historical mean. Intrinsic absorption in Lyβ is visible as well as absorption from O VI λλ1032, 1038, N v λλ1239, 1243, Si IV λλ1394, 1403, and C IV λλ1548, 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 × 1017 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 103 in both ionization parameter and column density.

Original languageEnglish
Pages (from-to)622-628
Number of pages7
JournalAstrophysical Journal
Volume467
Issue number2 PART I
Publication statusPublished - 1996
Externally publishedYes

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Keywords

  • Galaxies: active
  • Galaxies: individual (NGC 3516)
  • Galaxies: nuclei
  • Galaxies: seyfert
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kriss, G. A., Espey, B. R., Krolik, J. H., Tsvetanov, Z., Zheng, W., & Davidsen, A. F. (1996). Far-ultraviolet observations of NGC 3516 using the Hopkins Ultraviolet Telescope. Astrophysical Journal, 467(2 PART I), 622-628.