THE ORIGINS AND EVOLUTIONARY STATUS OF B STARS FOUND FAR FROM THE GALACTIC PLANE. II. KINEMATICS AND FULL SAMPLE ANALYSIS

This paper continues the analysis of faint high-latitude B stars from Martin. Here we analyze the kinematics of the stars and combine them with the abundance information from the first paper to classify each one. The sample contains 31 Population I runaways, 15 old evolved stars (including 5 blue horizontal-branch [BHB] stars, 3 post-HB stars, 1 pulsating helium dwarf, and 6 stars of ambiguous classification), 1 F dwarf, and 2 stars that do not easily fit in one of the other categories. No star in the sample unambiguously shows the characteristics of a young massive star formed in situ in the halo. The two unclassified stars are probably extreme Population I runaways. The low binary frequency and rotational velocity distribution of the Population I runaways imply that most were ejected from dense star clusters by the dynamic ejection scenario. However, we remain puzzled by the lack of runaway Be stars. We also confirm that PB 166 and HIP 41979 are both nearby solar-metallicity BHB stars.