We present measurements of the projected stellar rotation velocities ( v \sin i ) of a sample of 45 candidate field horizontal-branch ( HB ) stars spanning a wide range of effective temperature , from red HB stars with T _ { eff } \simeq 5000 { K } to blue HB stars with T _ { eff } of 17000 { K } .
Among the cooler blue HB stars ( T _ { eff } = 7500 – 11500 { K } ) , we confirm prior studies showing that although a majority of stars rotate at v \sin i < 15 { km } { s } ^ { -1 } , there exists a subset of “ fast rotators ” with v \sin i as high as 30– 35 { km } { s } ^ { -1 } .
All but one of the red HB stars in our sample have v \sin i < 10 { km } { s } ^ { -1 } , and no analogous rotation bimodality is evident .
We also identify a narrow-lined hot star ( T _ { eff } \simeq 16000 { K } ) with enhanced photospheric metal abundances and helium depletion , similar to the abundance patterns found among hot BHB stars in globular clusters , and four other stars that may also belong in this category .
We discuss details of the spectral line fitting procedure that we use to deduce v \sin i , and explore how measurements of field HB star rotation may shed light on the issue of HB star rotation in globular clusters .