| Issue |
A&A
Volume 405, Number 3, July III 2003
|
|
|---|---|---|
| Page(s) | 981 - 990 | |
| Section | Galactic structure, stellar clusters, and populations | |
| DOI | https://doi.org/10.1051/0004-6361:20030651 | |
| Published online | 30 June 2003 | |
The RR Lyrae star period – K-band luminosity relation of the globular cluster M 3*
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.
Received:
10
February
2003
Accepted:
24
April
2003
Abstract
That the RR Lyrae star period – K-band luminosity relation
is a promising tool as a distance indicator in
the Milky Way and Local Group of galaxies is apparent on observational and theoretical
grounds in the literature. Less clear is the
sensitivity of the relation, and consequently the physics of
horizontal branch stars,
to differences in stellar environment.
In this paper, the first measurement of the (fundamental) period –
K-band luminosity relation for
the central region of a globular cluster is presented. It is based on
a sample of seven RR Lyrae stars imaged with adaptive optics.
In addition, the relation for the outer region has been reanalyzed, and is
found to be in
good agreement with both the previous estimate by Longmore et al. (1990),
and with the inner region relation, especially when
irregular and double-mode RR Lyrae stars are excluded.
Importantly, there is no difference between the slope of
the inner and outer region relation within measurement uncertainties,
suggesting no difference in evolutionary state (luminosity).
Taking the M 3 distance modulus as 
mag, the
period–absolute K-band magnitude relation derived by linear
least squares fitting is:
for the inner region.
Excluding irregular variable stars, the outer region relation is:
. This good agreement provides further strong support
for the near-IR period-luminosity relation as a distance indicator.
Key words: stars: variables: RR Lyr / stars: distances / stars: horizontal branch / stars: imaging / instrumentation: adaptive optics
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.
© ESO, 2003
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