XMM-Newton RGS observation of the warm absorber in Mrk 279

Context. The Seyfert 1 galaxy Mrk 279 was observed by XMM-Newton in November 2005 on three consecutive orbits, showing significant short-scale variability (average soft band variation in flux ~20%). The source is known to host a two-component warm absorber with distinct ionisation states from a previous Chandra observation. Aims. We study the warm absorber in Mrk 279 and investigate any possible response to the short-term variations in the ionising flux and assess whether it has varied on a long-term timescale with respect to the Chandra observation. Methods. The XMM-Newton-RGS spectra of Mrk 279 were analysed in both the high- and low-flux states using the SPEX fitting package. Results. We find no significant changes in the warm absorber on either short timescales (~2 days) or longer ones (two and a half years), as the variations in the ionic column densities of the most relevant elements are below the 90% confidence level. The variations could still be present but are statistically undetected given the signal-to-noise ratio of the data. Starting from reasonable standard assumptions, we estimate the location of the absorbing gas, which is likely to be associated with the putative dusty torus rather than with the broad line region if the outflowing gas is moving at the escape velocity or greater.