Probing the outer edge of an accretion disk: a Her X-1 turn-on observed with RXTE M. Kuster, J. Wilms, R. Staubert, W. A. Heindl, R. E. Rothschild, N. I. Shakura and K. A. Postnov A&A, 443 3 (2005) 753-767 Published online: 15 November 2005 DOI: 10.1051/0004-6361:20042355