The period--luminosity relation for Mira variables in the Milky Way using Gaia DR3: a further distance anchor for $H_0$

Understand

Gaia DR3 parallaxes are used to calibrate preliminary period--luminosity relations of O-rich Mira variables in the 2MASS $J$, $H$ and $K_s$ bands using a probabilistic model accounting for variations in the parallax zeropoint and underestimation of the parallax uncertainties.

• The derived relations are compared to those measured for the Large and Small Magellanic Clouds, the Sagittarius dwarf spheroidal galaxy, globular cluster members and the subset of Milky Way Mira variables with VLBI parallaxes.
• The Milky Way linear $JHK_s$ relations are slightly steeper and thus fainter at short period than the corresponding LMC relations suggesting population effects in the near-infrared are perhaps larger than previous observational works have claimed.
• Models of the Gaia astrometry for the Mira variables suggest that, despite the intrinsic photocentre wobble and use of mean photometry in the astrometric solution of the current data reduction, the recovered parallaxes should be on average unbiased but with underestimated uncertainties for the nearest stars.