Stellar cooling, inelastic dark matter, and XENON
  We consider a novel scenario of dark photon-mediated inelastic dark matter to
explain the white dwarf cooling excess suggested by its luminosity function,
and the excess in electron recoil events at XENON1T. In the Sun, the dark
photon $A'$ is produced mainly via thermal processes, and the heavier dark
matter $\chi_2$ is produced by the scattering of halo dark matter $\chi_1$ with
electrons. The XENON1T signal arises primarily by solar $A'$ scattering, and
$A'$ emission by white dwarfs accommodates the extra cooling while maintaining
consistency with other stellar cooling observations. A tritium component in the
XENON1T detector is also required. We show for parameters that explain the
XENON1T data, but not the white dwarf cooling anomaly, that a second signal
peak may be buried in the XENON1T data and revealable at XENONnT. However, the
parameters that give the double peak in the spectrum are incompatible with
constraints from horizontal branch stars.
