M. Collaboration, M. Ahnen, S. Ansoldi, A. Antonelli, P. Antoranz, A. Babic, B. Banerjee, P. Bangale, U. de Almeida, J. Barrio und 244 andere Autor(en). (2015)cite arxiv:1512.04435Comment: Corresponding Authors: J. Becerra (josefa.becerra@nasa.gov), M. Nievas Rosillo (miguelnievas@ucm.es), M. Manganaro (manganaro@iac.es), F. Tavecchio (fabrizio.tavecchio@brera.inaf.it) To be published in The Astrophysical Journal Letters (ApJL).