On the distance of the globular cluster M4 (ngc 6121) using RR Lyrae stars. II. mid-infrared period–luminosity relations

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DOIResolve DOI: http://doi.org/10.1088/0004-637X/808/1/11
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TypeArticle
Journal titleThe Astrophysical Journal
ISSN1538-4357
Volume808
Issue1
Pages11
Subjectglobular clusters; individual (M$); star; RR Lyrae
AbstractNew mid-infrared (MIR) period–luminosity (PL) relations are presented for RR Lyræ variables in the globular cluster M4 (NGC 6121). Accurate photometry was obtained for 37 RR Lyræ variables using observations from the Infrared Array Camera on board the Spitzer Space Telescope. The dispersion of M4's PL relations is 0.056, and the uncertainty in the slope is 0.11 mag. Additionally, we established calibrated PL relations at 3.6 and 4.5 μm using published Hubble Space Telescope geometric parallaxes of five Galactic RR Lyræ stars. The resulting band-averaged distance modulus for M4 is μ=11.399 ± 0.007(stat) ± $0.080(syst) ± 0.015(cal) ± 0.020(ext). The systematic uncertainty will be greatly reduced when parallaxes of more stars become available from the GAIA mission. Optical and infrared period–color (PC) relations are also presented, and the lack of an MIR PC relation suggests that RR Lyræ stars are not affected by CO absorption in the 4.5 μm band.
Publication date
PublisherIOP Publishing
LanguageEnglish
AffiliationNRC Herzberg Astronomy and Astrophysics; National Research Council Canada
Peer reviewedYes
NPARC number23001574
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Record identifierd802fde8-0ad9-44ec-9cab-78cd3dcf8650
Record created2017-03-07
Record modified2017-03-30
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