RR Lyrae variables in Messier 53: Near-infrared Period–Luminosity relations and the calibration using Gaia Early Data Release 3

Kavli Affiliate: Gregory J. Herczeg

| First 5 Authors: Anupam Bhardwaj, Marina Rejkuba, Richard de Grijs, Soung-Chul Yang, Gregory J. Herczeg

| Summary:

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 modes (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 $1sigma$ 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 $-7pm3~mu$as in {it Gaia} Early Data Release 3 (EDR3), which
increases to $22pm2~mu$as if the parallax corrections are applied. We also
estimate a robust distance modulus, $mu_textrm{M53} = 16.403 pm 0.024$
(statistical) $pm 0.033$ (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 $omega$ Cen are used
to empirically calibrate a new RR Lyrae PLZ$_{K_s}$ relation, $K_s = -0.848
(0.007) -2.320 (0.006) log P + 0.166 (0.011) {rm[Fe/H]}$, anchored with {it
Gaia} EDR3 distances and theoretically predicted relations, and simultaneously
estimate precise RR Lyrae based distances to these globular clusters.

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