Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-03-29
Astrophys.J.517:L135-L138,1999
Astronomy and Astrophysics
Astrophysics
11 pages, 1 Postscript figure, uses aaspp4.sty, accepted for publication in ApJ Letters
Scientific paper
10.1086/312052
High-resolution optical spectra of thirteen blue horizontal-branch (BHB) stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (T_eff > 12000 K), helium is depleted by factors of 10 to 100 below solar, while iron is enhanced to three times the solar abundance, two orders of magnitude above the canonical metallicity [Fe/H] ~= -1.5 dex for this globular cluster. Nitrogen, phosphorus, and chromium exhibit even more pronounced enhancements, and other metals are also mildly overabundant, with the exception of magnesium, which stays very near the expected cluster metallicity. These photospheric anomalies are most likely due to diffusion --- gravitational settling of helium, and radiative levitation of the other elements --- in the stable radiative atmospheres of these hot stars. The effects of these mechanisms may have some impact on the photometric morphology of the cluster's horizontal branch and on estimates of its age and distance.
Behr Bradford Bartholomew
Cohen Judith Gamora
Djorgovski Stanislav G.
McCarthy James K.
No associations
LandOfFree
Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-227572