ner_tags: B-Person O B-Person O B-Organization O O O O O O O B-Person I-Person I-Person O O O O O O O O O O B-Person O O O O B-Location I-Location B-Grant I-Grant I-Grant B-Grant O O O O B-Fellowship I-Fellowship I-Fellowship I-Fellowship I-Fellowship I-Fellowship
tokens: DB and AG acknowledge ICRANet for partial support. All the authors thank Professor L. Stella for useful discussions at the beginning of the present project. AP acknowledges support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 267251 ‘Astronomy Fellowships in Italy (AstroFIt)’.