Journal Article

Period–luminosity relations of pulsating M giants in the solar neighbourhood and the Magellanic Clouds

V. Tabur, T. R. Bedding, L. L. Kiss, T. Giles, A. Derekas and T. T. Moon

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 409, issue 2, pages 777-788
Published in print December 2010 | ISSN: 0035-8711
Published online November 2010 | e-ISSN: 1365-2966 | DOI:
Period–luminosity relations of pulsating M giants in the solar neighbourhood and the Magellanic Clouds

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We analyse the results of a 5.5-yr photometric campaign that monitored 247 southern, semiregular variables with relatively precise Hipparcos parallaxes to demonstrate an unambiguous detection of red giant branch (RGB) pulsations in the solar neighbourhood. We show that Sequence A′ contains a mixture of asymptotic giant branch and RGB stars, as indicated by a temperature-related shift at the tip of the red giant branch. Large Magellanic Cloud (LMC) and Galactic sequences are compared in several ways to show that the period–luminosity sequence zero-points have a negligible metallicity dependence. We describe a new method to determine absolute magnitudes from pulsation periods and calibrate the LMC distance modulus using Hipparcos parallaxes to find μLMC= 18.54 ± 0.03 mag. Several sources of systematic error are discussed to explain discrepancies between the Massive Compact Halo Object and Optical Gravitational Lensing Experiment sequences in the LMC. We derive a relative distance modulus of the Small Magellanic Cloud relative to the LMC of Δμ= 0.41 ± 0.02 mag. A comparison of other pulsation properties, including period–amplitude and luminosity–amplitude relations, confirms that RGB pulsation properties are consistent and universal, indicating that the RGB sequences are suitable as high-precision distance indicators. The M giants with the shortest periods bridge the gap between G and K giant solar-like oscillations and M-giant pulsation, revealing a smooth continuity as we ascend the giant branch.

Keywords: methods: data analysis; stars: distances; stars: Population II; stars: variables: general; solar neighbourhood; Magellanic Clouds

Journal Article.  8112 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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