The variable ultraviolet absorption lines inthe Seyfert 1 galaxy NGC 3516.

Abstract

The ultraviolet spectrum of the Seyfert 1 galaxy NGC 3516 shows several intrinsic variable absorption lines. We analyze the properties of the CIV absorption profile, using IUE observations performed between 1978 and 1989. With certain assumptions which are supported by the observations and spelled out in the text, we are able to successfully model the absorption line with a narrow component (FWHM <~ 500 km s^-1^) and a broader component variable in width and depth. For all epochs the correlation between the column density (N_CIV_) of the broad component and the continuum flux at 1550 A is only fair, but this correlation is very good and linear during two periods of 1.5 years and 2.3 years. From this we deduce that the absorbing material is at a typical distance of 10^18^ cm from the ionizing source, and that it is in clouds of typical geometrical thickness of 10^15^ cm. A cloud stays on the line of sight for a period of 1 to 2 years.