Detecting massive satellites of extrasolar planets has now become feasible,
which led naturally to questions about their habitability. In a previous study
we presented constraints on the habitability of moons from stellar and
planetary illumination as well as from tidal heating. Here I refine our model
by including the effect of eclipses on the orbit-averaged illumination. Moons
in low-mass stellar systems must orbit their planet very closely to remain
bound, which puts them at risk of strong tidal heating. I first describe the
effect of eclipses on stellar illumination of satellites. Then I calculate the
orbit-averaged energy flux including illumination from the planet and tidal
heating. Habitability is defined by a scaling relation at which a moon loses
its water by the runaway greenhouse process. As a working hypothesis, orbital
stability is assumed if the moon's orbital period is less than 1/9 of the
planet's orbital period. Due to eclipses, a satellite in a close orbit can
experience a reduction in orbit-averaged stellar flux by up to about 6%. The
smaller the semi-major axis and the lower the inclination of the moon's orbit,
the stronger the reduction. I find a lower mass limit of ~0.2M_sun for exomoon
host stars to avoid the runaway greenhouse effect. Precise estimates depend on
the satellite's orbital eccentricity. Deleterious effects on exomoon
habitability may occur up to ~0.5M_sun. Although the habitable zone lies close
to low-mass stars, which allows for many transits of planet-moon binaries
within a given observation cycle, resources should not be spent to trace
habitable satellites around them. Gravitational perturbations by the star,
another planet, or another satellite induce eccentricities that likely make any
moon uninhabitable. Estimates for individual systems require dynamical
simulations that include perturbations among all bodies and tidal heating in
the satellite.Comment: 4 pages, 2 figures, accepted by A&
