A new low mass for the Hercules dSph: the end of a common mass scale for
  the dwarfs?
  We present a new mass estimate for the Hercules dwarf spheroidal galaxy
(dSph), based on the revised velocity dispersion obtained by Aden et al. (2009,
arXiv:0908.3489).
  The removal of a significant foreground contamination using newly acquired
Stromgren photometry has resulted in a reduced velocity dispersion. Using this
new velocity dispersion of 3.72 +/- 0.91 km/s, we find a mass of
M_300=1.9^{+1.1}_{-0.8} 10^6 M_sun within the central 300 pc, which is also the
half-light radius, and a mass of M_433=3.7_{-1.6}^{+2.2} 10^6 M_sun within the
reach of our data to 433 pc, significantly lower than previous estimates. We
derive an overall mass-to-light ratio of M_433/L=103^{+83}_{-48} M_sun/L_sun.
Our mass estimate calls into question recent claims of a common mass scale for
dSph galaxies.
  Additionally, we find tentative evidence for a velocity gradient in our
kinematic data of 16 +/- 3 km/s/kpc, and evidence of an asymmetric extension in
the light distribution at about 0.5 kpc. We explore the possibility that these
features are due to tidal interactions with the Milky Way. We show that there
is a self-consistent model in which Hercules has an assumed tidal radius of r_t
= 485 pc, an orbital pericentre of r_p = 18.5 +/- 5 kpc, and a mass within r_t
of M_{tid,r_t}=5.2 +/- 2.7 10^6 M_sun. Proper motions are required to test this
model. Although we cannot exclude models in which Hercules contains no dark
matter, we argue that Hercules is more likely to be a dark matter dominated
system which is currently experiencing some tidal disturbance of its outer
parts.
