The determination of for metal-poor A-type stars using and 2MASS , and magnitudes (original) (raw)

A&A 391, 1039-1052 (2002)

1 Kitt Peak National Observatory, National Optical Astronomy Observatories, Box 26732, Tucson, AZ 85726-6732, USA
2 Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, via del Fosso del Cavaliere, 00133 Roma, Italy
3 Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy e-mail: castelli@ts.astro.it

Corresponding author: T. Kinman, kinman@noao.edu

Received: 5 April 2002
Accepted: 27 May 2002

Abstract

Effective temperatures (_T_eff) can be determined from , and colours that are derived from 2MASS magnitudes. This gives another way to estimate the_T_eff of faint blue halo stars (V 15) whose temperatures are now usually deduced from . Transformations (adapted from Carpenter [CITE]) are used to change colours derived from the 2MASS data to the Johnson system. _T_eff is then derived from these colours using an updated Kurucz model. Tables are given to derive_T_eff as a function of , and for a variety of metallicities and suitable for blue horizontal branch and main sequence stars. The temperatures obtained in this way are compared with those in the recent literature for various stars with 5 ≤ V ≤ 15 and _T_eff in the range 6500 to 9500 K; systematic differences are ~100 K. An exception is the sample of BHB stars observed by Wilhelm et al. ([CITE]) whose _T_eff are significantly cooler than those we derive by an amount that increases with increasing temperature.

Key words: stars: fundamental parameters (temperatures) / stars: horizontal-branch

*

NOAO is operated by the Association of Universities for research in Astronomy, Inc., under contract with the National Science Foundation.

**

Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/1039

© ESO, 2002

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