1996/07/29 by S. Moehler, Sabine Moehler, Moehler, Sabine +5
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #History and Developments in Astronomy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9607151
LaTeX, 15 pages, 10 figures, A&A style, submitted to A&A
arxiv created 1996/07/29 · openalex publication_date 1996/07/29 · arxiv updated 2009/12/01 · openalex created_date 2022/10/06 · openalex updated_date 2026/07/28
We present spectroscopic analyses of 17 faint blue stars in the globular\ncluster NGC 6752. Effective temperatures, surface gravities, and helium\nabundances are determined and compared to theoretical predictions. All stars\nare helium deficient by factors of 3 to more than 100, indicative of\ngravitational settling of helium. Stars with Teff > 20000 K (sdBs) fit well to\nthe evolutionary tracks, whereas the cooler stars show lower surface gravities\nthan theoretically expected. This agrees with earlier findings by Moehler et\nal. (1995, A&A 294, 65) for the faint blue stars in M 15. Deriving masses from\nthe atmospheric parameters and the cluster distance leads to a mean mass of the\nsdB stars of 0.50 M0 and a standard deviation of about 0.043 dex, which is\nbelow the value derived of the observational errors and thus consistent with a\nvery narrow mass distribution. The mean mass is in good agreement with the\n(0.49 +/- 0.02) M0 expected if sdB stars are extreme horizontal branch stars.\nThe cooler stars show a significantly lower mean mass of 0.30 M0 in agreement\nwith the findings of Moehler et al. (1995, M 15) and de Boer et al. (1995, A&A\n303, 95; NGC 6397). The problems presented by the different mass distributions\nof BHB and sdB stars within one cluster are discussed.\n