JWST Observations of RR Lyrae in Leo P

We analyze co-spatial HST/ACS and JWST/NIRCam time-series photometric observations of RR Lyrae in the low-metallicity dwarf galaxy Leo P. This study provides a new opportunity to explore the properties of and potential for metal-poor RR Lyrae studies with JWST using well-understood relationships from past HST work. We identify 20 RR Lyrae in the HST imaging and 15 RR Lyrae in the JWST imaging. We determine the periods, amplitudes, and mean magnitudes for each of the RR Lyrae. We fit the Period-Wesenheit-Metallicity (PWZ) function to the HST RR Lyrae population, and obtain a Gaia-consistent RR Lyrae-based distance to Leo P of μ= 26.04 plus or minus0.07 (1.61 plus or minus0.06 Mpc), consistent with existing distance measurements. We determine a JWST-based PWZ using Leo P data along with previous JWST RR Lyrae observations in WLM. The simultaneous fit decreases the mean fractional uncertainty by 31% on the slope and by 11% on the intercept, increasing the constraining power as compared to the existing calibration.