The red clump absolute magnitude based on revised Hipparcos parallaxes

• Published in: Astronomy and astrophysics (Berlin) Vol. 488; no. 3; pp. 935 - 941
• Main Author: Groenewegen, M. A. T.
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.09.2008
• Subjects: Astronomy; cosmology: distance scale; Earth, ocean, space; Exact sciences and technology; stars: distances; Bright star; cosmology: distance scale; Digital simulation; Distance scale; Absolute magnitude; stars: distances; Astronomical catalogues; Cosmology; Selection criterion; Models; Star clusters; Corrections
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361:200810201

Context. Over the past decade the use of the red clump (RC) as distance indicator has increased in importance as this evolutionary phase is well populated and a good local calibration exists. Aims. The absolute calibration of the RC in the I and K band is investigated again based on the recently published revised Hipparcos parallaxes. Methods. A numerical model is developed that takes the various selection criteria and the properties of the Hipparcos catalogue into account. The biases involved in applying certain selections are estimated with this model. Results. The absolute magnitudes that are found are $M_{I} = -0.22 \pm 0.03$ and $M_{K} = -1.54 \pm 0.04$ (on the 2MASS system). The I-band value is in good agreement with previous determinations, the K-band value is fainter than previously quoted, and this seems to be related to a selection bias whereby accurate K-magnitudes are only available for relatively few bright stars. Applying population corrections to the absolute K magnitude of RC stars in clusters supports the fainter magnitude scale.