| タイトル | An ultraviolet-visible investigation of the globular cluster NGC 1851 |
| 著者（英） | Greason, Michael R.; Roberts, Morton S.; Cheng, Kwang-Ping; Smith, Andrew M.; Hintzen, Paul M. N.; Landsman, Wayne B.; O'Connell, Robert W.; Maran, Stephen P.; Bohlin, Ralph C.; Parise, Ronald A. |
| 著者所属（英） | NASA Goddard Space Flight Center; NASA Headquarters |
| 発行日 | 1994-03-01 |
| 言語 | eng |
| 内容記述 | Two-color ultraviolet images of the globular cluster NGC 1851 were obtained with the Ultraviolet Imaging Telescope (UIT) during the 1990 December Astro-1 Spacelab mission. A total of 133 stars are detected at 2490 A and 74 stars at 1520 A. An ultraviolet color-magnitude diagram based on the 46 well-photometered stars that appear in both images is presented. Thirty-nine of the 45 horizontal branch (HB) stars fall below the zero-age horizontal branch (ZAHB) of Z = 0.001 and Y = 0.23 predicted by Sweigart by as much as 0.6 mag if the interstellar reddening to the cluster is E(B - V) = 0.02. Supporting ground-based V and B observations, however, show excellent correlation with the same model ZAHB. A newly detected hot subdwarf star with T(sub eff) is approximately 26,000 K appears to be an extreme horizontal branch star. The measured flux for this star also falls approximately 0.6 mag below the position on the color-magnitude diagrams (CMD) predicted by parameters derived from ground-based spectroscopy by Landsman. The far-ultraviolet image is dominated by the ultraviolet-bright member star UV 5, which contributes 30% of the total flux at 1520 A. The UIT photometry is consistent with the classification of UV 5 as a post-asymptotic giant branch (PAGB) star. To a limit of 16.5 mag at 1520 A we find no ultraviolet counterpart within 6 minutes of the position of the X-ray source MX 0513-40. |
| NASA分類 | ASTROPHYSICS |
| レポートNO | 95A65475 |
| 権利 | Copyright |
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