  Several stellar systems (white dwarfs, red giants, horizontal branch stars
and possibly the neutron star in the supernova remnant Cassiopeia A) show a
mild preference for a non-standard cooling mechanism when compared with
theoretical models. This exotic cooling could be provided by Weakly Interacting
Slim Particles (WISPs), produced in the hot cores and abandoning the star
unimpeded, contributing directly to the energy loss. Taken individually, these
excesses do not show a strong statistical weight. However, if one mechanism
could consistently explain several of them, the hint could be significant. We
analyze the hints in terms of neutrino anomalous magnetic moments, minicharged
particles, hidden photons and axion-like particles (ALPs). Among them, the ALP
or a massless HP represent the best solution. Interestingly, the hinted ALP
parameter space is accessible to the next generation proposed ALP searches,
such as ALPS II and IAXO and the massless HP requires a multi TeV energy scale
of new physics that might be accessible at the LHC.
