Global fits of axion-like particles to XENON1T and astrophysical data
  The excess of electron recoil events seen by the XENON1T experiment has been
interpreted as a potential signal of axion-like particles (ALPs), either
produced in the Sun, or constituting part of the dark matter halo of the Milky
Way. It has also been explained as a consequence of trace amounts of tritium in
the experiment. We consider the evidence for the solar and dark-matter ALP
hypotheses from the combination of XENON1T data and multiple astrophysical
probes, including horizontal branch stars, red giants, and white dwarfs. We
briefly address the influence of ALP decays and supernova cooling. While the
different datasets are in clear tension for the case of solar ALPs, all
measurements can be simultaneously accommodated for the case of a sub-dominant
fraction of dark-matter ALPs. Nevertheless, this solution requires the tuning
of several a priori unknown parameters, such that for our choices of priors a
Bayesian analysis shows no strong preference for the ALP interpretation of the
XENON1T excess over the background hypothesis.
