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RR Lyrae Variables in Messier 53: Near-infrared Period-Luminosity Relations and the Calibration Using Gaia Early Data Release 3
  • Anupam Bhardwaj; 양성철; Chou-Choong Ngeow;
  • 2021-03-10
  • ASTROPHYSICAL JOURNAL 909 2 : 200-1~200-15
We present new near-infrared, JHK s , period?luminosity relations (PLRs) for RR Lyrae variables in the Messier 53 (M53 or NGC 5024) globular cluster. Multi-epoch JHK s observations, obtained with the WIRCam instrument on the 3.6 m Canada?France?Hawaii Telescope, are used for the first time to estimate precise mean magnitudes for 63 RR Lyrae stars in M53 including 29 fundamental-mode (RRab) and 34 first-overtone mode (RRc) variables. The JHK s -band PLRs for RR Lyrae stars are best constrained for RRab types with a minimal scatter of 22, 23, and 19 mmag, respectively. The combined sample of RR Lyrae is used to derive the K s -band PLR, K s = - 2.303 ( 0.063 ) log P + 15.212 ( 0.016 ) , exhibiting a 1σ dispersion of only 0.027 mag. Theoretical period? luminosity?metallicity (PLZ) relations are used to predict parallaxes for 400 Galactic RR Lyrae, resulting in a median parallax zero-point offset of ?7 ± 3 μas in Gaia Early Data Release 3 (EDR3), which increases to 22 ± 2 μas if the parallax corrections are applied. We also estimate a robust distance modulus, μ M53 = 16.403 ± 0.024 (statistical) ± 0.033 (systematic) mag, to M53 based on theoretical calibrations. Homogeneous and precise mean magnitudes for RR Lyrae in M53 together with similar literature data for M3, M4, M5, and ω Cen are used to empirically calibrate a new RR Lyrae PLZ K s relation, K s = - 0.848 ( 0.007 ) - 2.320 ( 0.006 ) log P + 0.166 ( 0.011 )[ Fe H ] , anchored with Gaia EDR3 distances and theoretically predicted relations, and to simultaneously estimate precise RR Lyrae-based distances to these globular clusters.