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- Title
Red giant branch bump brightness in 7 metal-poor globular clusters obtained with GAIA DR2.
- Authors
Song, Fen; Yuan, Zunli; Li, Yan; Wu, Xuchao; Pietrinferni, Adriano; Poon, Helen; Wu, Tao; Nie, Jundan; Song, Hanfeng; Han, Cheng; Yang, Ye; Li, Yuxuan; Bai, Xingming
- Abstract
The identification of the red giant branch bump brightness in metal-poor globular clusters is important for low-mass stellar evolution. The release of Gaia DR2 prompted us to revisit the red giant branch bump (RGBB) in galactic globular clusters. We apply a popular nonparametric density estimation approach, kernel density estimation (KDE), to explore the position of RGBB in 7 metal-poor globular clusters (GCs). The G and V magnitudes of the RGBB according to our clustering algorithm, G B , K and V B , K , respectively show the RGB bump magnitude detected by the KDE method in G band and V band. They show the overdensity location in the luminosity function of the RGB stars. Based on the results derived by KDE, a maximum-likelihood analysis via a Markov Chain Monte Carlo (MCMC) approach is adopted to detect the RGB bump feature and obtain more accurate RGBB brightnesses in G band and V band for the samples. We find that the red giant branch bump brightness becomes fainter as the global metallicity increases in clusters with [ M / H ] ≤ − 1.4 . We present the empirical relation between the global metallicity [ M / H ] and absolute magnitude M V of the red giant branch bump for clusters with [ M / H ] ≤ − 1.4 . We verify that discrepancies between observations and theory for metal-poor globular clusters with [ M / H ] ≤ − 1.4 .
- Subjects
RED giants; STELLAR luminosity function; MARKOV chain Monte Carlo; PROBABILITY density function; STELLAR evolution; GLOBULAR clusters
- Publication
Astrophysics & Space Science, 2022, Vol 367, Issue 3, p1
- ISSN
0004-640X
- Publication type
Article
- DOI
10.1007/s10509-022-04058-1