A search for field horizontal-branch stars near the south galactic pole

• Grant number: 10/02722-5
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: April 01, 2010
• End date: September 30, 2010
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Silvia Cristina Fernandes Rossi
• Grantee: Silvia Cristina Fernandes Rossi
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• City of the host institution: São Paulo

Abstract

Searches for field horizontal-branch (FHB) stars in the halo of the Galaxy in the past have been carried out by severaltechniques, such as objective-prism surveys and visual or infrared photometric surveys. By choosing adequate colorcriteria, it is possible to improve the efficiency of identifying bona fide FHB stars among the other objects that exhibitsimilar characteristics, such as main-sequence A-stars, blue stragglers, subdwarfs, etc. In this work, we report theresults of a spectroscopic survey carried out near the south Galactic pole intended to validate FHB stars originallyselected from the HK objective-prism survey of Beers and colleagues, based on near-infrared color indices. Acomparison between the stellar spectra obtained in this survey with theoretical stellar atmosphere models allows usto determine Teff, logg, and [Fe/H] for 13 stars in the sample. Stellar temperatures were calculated from measured(B-V)o, when this measurement was available (16 stars). The color index criteria adopted in this work are shown tocorrectly classify 30% of the sample as FHB, 25% as non-FHB (main-sequence stars and subdwarfes), whereas 40%could not be distinguished between FHB and main-sequence stars.We compare the efficacy of different color criteriain the literature intended to select FHB stars, and discuss the use of the MgII 4481 line to estimate the metallicity. (AU)