文章基本信息

标题：On the RR Lyrae Stars in Globulars. V. The Complete Near-infrared (JHKs) Census of ω Centauri RR Lyrae Variables
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作者：V. F. Braga ; P. B. Stetson ; G. Bono 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：155
期号：3
页码：1-27
DOI：10.3847/1538-3881/aaadab
语种：English
出版社：American Institute of Physics
摘要：We present a new complete near-infrared (NIR, JHKs) census of RR Lyrae stars (RRLs) in the globular ω Cen (NGC 5139). We collected 15,472 JHKs images with –8 m class telescopes over 15 years (2000–2015) covering a sky area around the cluster center of 60×34 arcmin2. These images provided calibrated photometry for 182 out of the 198 cluster RRL candidates with 10 to 60 measurements per band. We also provide new homogeneous estimates of the photometric amplitude for 180 (J), 176 (H) and 174 (Ks) RRLs. These data were supplemented with single-epoch JKs magnitudes from VHS and with single-epoch H magnitudes from 2MASS. Using proprietary optical and NIR data together with new optical light curves (ASAS-SN) we also updated pulsation periods for 59 candidate RRLs. As a whole, we provide JHKs magnitudes for 90 RRab (fundamentals), 103 RRc (first overtones) and one RRd (mixed-mode pulsator). We found that NIR/optical photometric amplitude ratios increase when moving from first overtone to fundamental and to long-period (P >0.7 days) fundamental RRLs. Using predicted period luminosity–metallicity relations, we derive a true distance modulus of 13.674± 0.008±0.038 mag (statistical error and standard deviation of the median) based on spectroscopic iron abundances, and of 13.698±0.004±0.048 mag based on photometric iron abundances. We also found evidence of possible systematics at the 5%–10% level in the zero-point of the period–luminosity relations based on the five calibrating RRLs whose parallaxes had been determined with the HST.
关键词：globular Clusters: individual (ω Centauri);stars: distances;stars: horizontal-branch;stars: variables: RR Lyrae