Axion and neutrino bounds improved with new calibrations of the tip of
  the red-giant branch using geometric distance determinations
  The brightness of the tip of the red-giant branch (TRGB) allows one to
constrain novel energy losses that would lead to a larger core mass at helium
ignition and thus to a brighter TRGB than expected by standard stellar models.
The required absolute TRGB calibrations strongly improve with reliable
geometric distances that have become available for the galaxy NGC 4258 that
hosts a water megamaser and to the Large Magellanic Cloud based on 20 detached
eclipsing binaries. Moreover, we revise a previous TRGB calibration in the
globular cluster $\omega$ Centauri with a recent kinematical distance
determination based on Gaia DR2 data. All of these calibrations have similar
uncertainties and they agree with each other and with recent dedicated stellar
models. Using NGC 4258 as the cleanest extra-galactic case, we thus find an
updated constraint on the axion-electron coupling of $g_{ae}<1.6\times10^{-13}$
and $\mu_\nu<1.5\times10^{-12}\mu_{\rm B}$ (95\% CL) on a possible neutrino
dipole moment, whereas $\omega$ Centauri as the best galactic target provides
instead $g_{ae}<1.3\times10^{-13}$ and $\mu_\nu<1.2\times10^{-12}\mu_{\rm B}$.
The reduced observational errors imply that stellar evolution theory and
bolometric corrections begin to dominate the overall uncertainties.
