A parametrization to test black hole candidates with the spectrum of thin disks Nan Lin, Naoki Tsukamoto, M. Ghasemi-Nodehi and Cosimo Bambi Eur. Phys. J. C, 75 12 (2015) 599 Published online: 17 December 2015 DOI: 10.1140/epjc/s10052-015-3837-3