Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997nasa.reptu....k&link_type=abstract
Technical Report, NASA/CR-97-112949; NAS 1.26:112949 Dept. of Physics and Astronomy
Astronomy and Astrophysics
Astronomy
Acoustic Velocity, Ultraviolet Absorption, Seyfert Galaxies, Energy Absorption, K Lines, Line Spectra, X Rays, Space Transportation System Flights, Scattering, Turbulence, Photoionization
Scientific paper
We obtained ASCA spectra of the Seyfert 1 galaxy NGC 3516 in March 1995. 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 0 VII and 0 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 K(alpha) emission line from cold material is present as well as a broad Fe K(alpha) 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 x 1022/sq cm, adding a lower ionization absorber with U = 0.32 and a total column of 6.9 x 1021/sq cm 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 at 90% confidence. Turbulence at the sound speed of the photoionized gas provides the best fit. None of the warm absorber models fit 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.
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