The near-infrared spectral index of Sagittarius A* derived from Ks- and H-band flare statistics M. Bremer, G. Witzel, A. Eckart, M. Zamaninasab, R. M. Buchholz, R. Schödel, C. Straubmeier, M. García-Marín and W. Duschl A&A, 532 (2011) A26 Published online: 14 July 2011 DOI: 10.1051/0004-6361/201016134