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| Paper: |
A Metal--Rich Blue Horizontal Branch in NGC 6791 |
| Volume: |
92, Formation of the Galactic Halo. . . . Inside and Out |
| Page: |
184 |
| Authors: |
Green, Elizabeth M.; Liebert, James; Peterson, Ruth C. |
| Abstract: |
The old open cluster NGC 6791 is unique in many ways. It is the only known old disk cluster with greater than solar abundance ([Fe/H] = +0.3), it is among the two or three oldest open clusters of any metallicity (age ~ \ 10 Gyr), and it is also one of the most populous. The discovery of five subdwarf O and B stars in NGC 6791 makes it the only cluster with [Fe/H] >= -0.9 having a blue horizontal branch in addition to the normal red one. In this paper, we report evidence for membership of four new blue stars in NGC 6791, spread uniformly along the horizontal branch between the subdwarfs and the instability strip. We summarize the evidence for and against a binary origin for these stars. |
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