ASCA OBSERVATIONS OF THE COMPOSITE WARM ABSORBER IN NGC-3516

We obtained X-ray spectra of the Seyfert 1 galaxy NGC 3516 in 1995 Mar ch using the Japanese X-ray satellite, ASCA. Simultaneous far-UV obser vations were obtained with the Hopkins Ultraviolet Telescope on the As tro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed powe r law of energy index 0.78. The low-energy absorbing column is signifi cantly less than previously seen. Prominent O VII and O VIII absorptio n edges are visible, but, consistent with the much lower total absorbi ng 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 F e K alpha line. These features are similar to those reported in other Seyfert 1 galaxies. A single warm absorber model provides only an impe rfect description of the low-energy absorption. In addition to a highl y ionized absorber with ionization parameter U = 1.66 and a total colu mn density of 1.4 x 10(22) cm(-2), adding a lower ionization absorber with U = 0.32 and a total column of 6.9 x 10(21) 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 photoion ized gas provides the best fit. None of the warm absorber models fitte d to the X-ray spectrum can match the observed equivalent widths of al l the UV absorption lines. Accounting for the X-ray and UV absorption simultaneously requires an absorbing region with a broad range of ioni zation parameters and column densities.