First firm spectral classification of an early-B pre-main-sequence star: B275 in M 17 B. B. Ochsendorf, L. E. Ellerbroek, R. Chini, O. E. Hartoog, V. Hoffmeister, L. B. F. M. Waters and L. Kaper A&A, 536 (2011) L1 Published online: 02 December 2011 DOI: 10.1051/0004-6361/201118089