Spectral monitoring of RX J1856.5-3754 with XMM-Newton - Analysis of EPIC-pn data N. Sartore, A. Tiengo, S. Mereghetti, A. De Luca, R. Turolla and F. Haberl A&A, 541 (2012) A66 Published online: 30 April 2012 DOI: 10.1051/0004-6361/201118489