ASCA observations of the composite warm absorber in NGC 3516

G. A. Kriss, J. H. Krolik, C. Otani, B. R. Espey, T. J. Turner, T. Kh, Z. Tsvetanov, T. Takahashi, A. F. Davidsen, M. Tashiro, W. Zheng, S. Murakami, R. Petre, T. Mihara

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We obtained X-ray spectra of the Seyfert 1 galaxy NGC 3516 in 1995 March using the Japanese X-ray satellite, ASCA. Simultaneous far-UV observations were obtained with the Hopkins Ultraviolet Telescope on the Astro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed power law of energy index 0.78. The low-energy absorbing column is significantly less than previously seen. Prominent O vu and O VIII absorption edges are visible, but, consistent with the much lower total absorbing column, no Fe K absorption edge is detectable. A weak, narrow Fe Kα emission line from cold material is present as well as a broad Fe Kα line. These features are similar to those reported in other Seyfert 1 galaxies. A single warm absorber model provides only an imperfect description of the low-energy absorption. In addition to a highly ionized absorber with ionization parameter U = 1.66 and a total column density of 1.4 × 1022 cm-2, adding a lower ionization absorber with U = 0.32 and a total column of 6.9 × 1021 cm-2 significantly improves the fit. The contribution of resonant line scattering to our warm absorber models limits the Doppler parameter to less than 160 km s-1 at 90% confidence. Turbulence at the sound speed of the photoionized gas provides the best fit. None of the warm absorber models fitted to the X-ray spectrum can match the observed equivalent widths of all the UV absorption lines. Accounting for the X-ray and UV absorption simultaneously requires an absorbing region with a broad range of ionization parameters and column densities.

Original languageEnglish
Pages (from-to)629-635
Number of pages7
JournalAstrophysical Journal
Issue number2 PART I
Publication statusPublished - 1 Jan 1996



  • Galaxies: Seyfert
  • Galaxies: active
  • Galaxies: individual (NGC 3516)
  • Galaxies: nuclei
  • X-ray: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Kriss, G. A., Krolik, J. H., Otani, C., Espey, B. R., Turner, T. J., Kh, T., Tsvetanov, Z., Takahashi, T., Davidsen, A. F., Tashiro, M., Zheng, W., Murakami, S., Petre, R., & Mihara, T. (1996). ASCA observations of the composite warm absorber in NGC 3516. Astrophysical Journal, 467(2 PART I), 629-635.