Journal Article

The kinematics and zero-point of the log <i>P</i>–〈<i>M<sub>K</sub></i>〉 relation for Galactic RR Lyrae variables via statistical parallax

A. K. Dambis

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 1, pages 553-569
Published in print June 2009 | ISSN: 0035-8711
Published online June 2009 | e-ISSN: 1365-2966 | DOI:
The kinematics and zero-point of the log P–〈MK〉 relation for Galactic RR Lyrae variables via statistical parallax

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We use accurate absolute proper motions and Two-Micron All-Sky Survey Ks-band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the Ks-band period–luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be [U0(Halo), V0(Halo), W0(Halo)]= (−12 ± 10, −217 ± 9, −6 ± 6) km s−1 and [U0(Disc), V0(Disc), W0(Disc)]= (−15 ± 7, −44 ± 7, −25 ± 5) km s−1, respectively, and the corresponding components of the velocity-dispersion ellipsoids, [σVR(Halo), σVθ(Halo), σW(Halo)]= (167 ± 9, 86 ± 6, 78 ± 5) km s−1 and [σVR(Disc), σVθ(Disc), σW(Disc)]= (55 ± 7, 44 ± 6, 30 ± 4) km s−1, respectively. The fraction of thick-disc stars is estimated at 0.25 ± 0.03. The corrected infrared period–luminosity relation is , implying a Large Magellanic Cloud (LMC) distance modulus of 18.27 ± 0.08 and a solar Galactocentric distance of 7.58 ± 0.40 kpc. Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way.

Keywords: stars: distances; stars: horizontal branch; stars: kinematics; stars: variables: other; Galaxy: kinematics and dynamics; distance scale

Journal Article.  8643 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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