Multiwavelength Period-Luminosity and Period-Luminosity-Color relations
  at maximum-light for Mira variables in the Magellanic Clouds
  We present Period-Luminosity and Period-Luminosity-Color relations at
maximum-light for Mira variables in the Magellanic Clouds using time-series
data from the Optical Gravitational Lensing Experiment (OGLE-III) and {\it
Gaia} data release 2. The maximum-light relations exhibit a scatter typically
up to $\sim 30\%$ smaller than their mean-light counterparts. The apparent
magnitudes of Oxygen-rich Miras at maximum-light display significantly smaller
cycle-to-cycle variations than at minimum-light. High-precision photometric
data for Kepler Mira candidates also exhibit stable magnitude variations at the
brightest epochs while their multi-epoch spectra display strong Balmer emission
lines and weak molecular absorption at maximum-light. The stability of
maximum-light magnitudes for Miras possibly occurs due to the decrease in the
sensitivity to molecular bands at their warmest phase. At near-infrared
wavelengths, the Period-Luminosity relations of Miras display similar
dispersion at mean and maximum-light with limited time-series data in the
Magellanic Clouds. A kink in the Oxygen-rich Mira Period-Luminosity relations
is found at 300 days in the $VI$-bands which shifts to longer-periods ($\sim
350$~days) at near-infrared wavelengths. Oxygen-rich Mira Period-Luminosity
relations at maximum-light provide a relative distance modulus, $\Delta \mu =
0.48\pm0.08$~mag, between the Magellanic Clouds with a smaller statistical
uncertainty than the mean-light relations. The maximum-light properties of
Miras can be very useful for stellar atmosphere modeling and distance scale
studies provided their stability and the universality can be established in
other stellar environments in the era of extremely large telescopes.
