X-ray/UV campaign on the Mrk 279 outflow: Density diagnostics in Active Galactic Nuclei using O v K-shell absorption linesJ. S. Kaastra, A. J. J. Raassen, R. Mewe, N. Arav, E. Behar, E. Costantini, J. R. Gabel, G. A. Kriss, D. Proga, M. Sako and K. C. SteenbruggeA&A, 428 1 (2004) 57-66DOI: https://doi.org/10.1051/0004-6361:20041434