Further constraints on the warm absorber in MR 2251-17.8 from GINGA and EXOSAT observations.

Abstract

Analysis of a Ginga observation of MR 2251 - 17.8 is presented. The source is in a relatively low emission state, with a high absorbing column density. This result is consistent with the previous EXOSAT observations, where a strong correlation between the flux and the column density was detected. The Ginga spectrum and the entire EXOSAT spectral data set for MR 2251 - 17.8 are fitted using a self-consistent model for the opacity of partially ionized material (a `warm absorber'). The ionization state of the gas is found to be strongly correlated with the source luminosity, showing the validity of the model used, and allowing constraints to be placed on the location, geometry and density of the absorbing material. The existence of a spectral component due to reflection from an inner disc surrounding the central source, such has been found in other active galaxies, is also investigated.