Cyclotron line energy in Hercules X-1: stable after the decayR. Staubert, L. Ducci, L. Ji, F. Fürst, J. Wilms, R. E. Rothschild, K. Pottschmidt, M. Brumback and F. HarrisonA&A, 642 (2020) A196DOI: https://doi.org/10.1051/0004-6361/202038855
