Spectral types in the ORI OB1 association.

Spectral types are derived for 152 stars in the Northwest, Belt, and Outer Sword regions. The classifications show that the following are present: (1) stars above the ZAMS in the O9B3 and the B7-A3 regions; most of these have greater luminosities than class V or are double-lined binaries or peculiar stars; (2) eleven Ap stars of which three are Si rich, two are He rich, five are He poor, and one is Mg poor; (3) four moderate Be stars; (4) only two stars with broad hydrogen lines like the ones that are so prevalent in the Orion Nebula Cluster; (5)14 "sn" stars that have both sharp and broad He I lines, perhaps due to tenuous shells; (6) one classical shell star; (7) several Sirius-type Am stars, although most of the Am stars in the region are foreground stars.