EXOSAT Observations of the Seyfert 1 Galaxy NGC 3516

Abstract

Results of the X-ray spectra (0.1-10 keV) of the Seyfert galaxy NGC 3516 are presented based on the EXOSAT observations obtained on four epochs between 1985/308 and 1985/340. The data were obtained from the EXOSAT archives. The soft X-ray (0.1-2 keV) flux of this galaxy varied by a factor of ~3 on the time scales of 2 days, and that for the hard X-ray (2-10 keV) flux varied by a factor of ~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 (N_H_~10^22^ cm^-2^) have been detected in the spectrum of this galaxy. An emission line detected with a high significance (>99.9%) 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 red-shifted 6.7 keV helium-like iron line produced in an optically thin hot plasma of temperature around ~10^8^ K. Measured equivalent width of the line ranges between 106 and 1240 eV. A very interesting feature of this line is that it has displayed very broad (~1.0 keV) line width which may be the first observational result on the broadening of the Fe K-shell lines in an AGN, NGC 3516.