EXOSAT observations of the Seyfert 1 galaxy NGC 3516

Abstract

This study presents results of the X-ray spectra (0.1-10 keV) of the Seyfert galaxy NGC 3516 on the basis of Exosat observations obtained on four epochs between 1985/308 and 1985/340. The soft X-ray (0.2-2 keV) flux of this galaxy varied by a factor of about 3 on the time scales of 2 d, and that for the hard X-ray (2-10 keV) flux varied by a factor of about 1.5 over the period of a month. The observed spectra are best fitted by a power-law, uniform absorption, and a Gaussian line model. Best-fit parameters of this model suggest that NGC 3516 is a flat spectrum source. Weak soft excess and significant intrinsic absorption (about 10 exp 22/sq cm) were detected in the spectrum of this galaxy. An emission line detected with a high significance (greater than 99.9 percent) around 6.0 keV could be the redshifted 6.4-keV iron line due to the fluorescence of thick cold iron present around the nucleus of NGC 3516 or due to the redshifted 6.7-keV helium-like iron line produced in an optically thin hot plasma of temperature around 10 exp 8 K.