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| Paper: |
Axial Rotation and Incidence of Binaries Among BMP Stars |
| Volume: |
92, Formation of the Galactic Halo. . . . Inside and Out |
| Page: |
49 |
| Authors: |
Preston, George W. |
| Abstract: |
An echelle survey conducted at Las Campanas Observatory during the past four years has been used to study the chemical heterogeneity, derive axial rotations (V_e sini) and estimate the spectroscopic binary fraction for a sample of blue metal-poor stars (hereafter BMP). Metal abundances estimated from the strength of CaII(K) exceed the BMP photometric lower bound, [Fe/H] < --1, for 25 percent of the sample. Slopes of blanketing vectors, d(U-B)/d(B-V), are used to calculate the blanketed colors, (B-V)bl, that BMPs would have were their Fe abundances increased to the solar value. The mean projected rotational velocity of BMP stars exhibits a decline with increasing (B-V)bl similar to that found for ordinary A- and F- type stars in the solar neighborhood. Examination of radial velocity dispersions suggests that the fraction of BMP stars in binaries with P<1500 days is probably larger ( ~ 0.35) than the corresponding binary fractions ( ~ 0.17) of disk main sequence stars. This difference can arise, if a significant fraction of the BMP stars are blue stragglers among which the binary fraction is sufficiently high. |
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