The first Δa observations of three globular clusters
- Author(s)
- Ernst Paunzen, I. Kh. Iliev, Olga Pintado, Hubert Baum, Hans Michael Maitzen, Martin Netopil, A. Önehag, M. Zejda, L Fraga
- Abstract
Globular clusters are main astrophysical laboratories to test and modify evolutionary models. Thought to be rather homogeneous in their local elemental distribution of members, results suggest a wide variety of chemical peculiarities. Besides different main sequences, believed to be caused by different helium abundances, peculiarities of blue horizontal-branch stars and on the red giant branch were found. This whole zoo of peculiar objects has to be explained in the context of stellar formation and evolution. The tool of Δ photometry is employed in order to detect peculiar stars in the whole spectral range. This three filter narrowband system measures the flux distribution in the region from 4900 to 5600 Å in order to find any peculiarities around 5200 Å. It is highly efficient to detect classical chemically peculiar stars of the upper main sequence, Be/Ae, shell and metal-weak objects in the Milky Way and Magellanic Clouds. We present Δa photometry of 2266 stars from 109 individual frames for three globular clusters (NGC 104, NGC 6205, and NGC 7099). A comparison with published abundances, for three horizontal-branch stars, only, yields an excellent agreement. According to the 3s detection limit of each globular cluster, about 3 per cent of the stars lie in abnormal regions in the diagnostic diagrams. The first observations of three widely different aggregates give very promising results, which will serve as a solid basis for follow-up observations including photometric as well as spectroscopic studies.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Masaryk University, Bulgarian Academy of Sciences (BAS), Universidad Nacional de Tucumán, Uppsala University, Southern Observatory for Astrophysical Research, Laboratório Nacional de Astrofísica
- Journal
- Monthly Notices of the Royal Astronomical Society
- Volume
- 443
- Pages
- 2492-2498
- No. of pages
- 7
- ISSN
- 0035-8711
- DOI
- https://doi.org/10.1093/mnras/stu1276
- Publication date
- 09-2014
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy, 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/eb17e199-930e-47dc-a468-14d0d32f894a