On the mass of the Galactic star cluster NGC 4337
  Only a small number of galactic open clusters survives for longer than few
hundred million years. Longer lifetimes are routinely explained in term of
larger initial masses, particularly quiet orbits, and off-plane birth-places.
We derive in this work the actual mass of NGC 4337, one of the few open
clusters in the Milky Way inner disk that managed to survive for about 1.5 Gyr.
We derive its mass in two different ways. First, we exploit an unpublished
photometric data set in the UBVI passbands to estimate -using star counts- the
cluster luminosity profile, and luminosity and mass function, and hence its
actual mass both from the luminosity profile and from the mass function.This
data-set is also used to infer crucial cluster parameters, as the cluster
half-mass radius and distance. Second, we make use of a large survey of cluster
star radial velocities to derive dynamical estimates for the cluster mass.
Under the assumption of virial equilibrium and neglecting the external
gravitational field leads to values for the mass significantly larger than
those obtained by mean of observed density distribution or with the mass
function but still marginally compatible with the inferred values of the
invisible mass in form of both low mass stars or remnants of high mass stars in
the cluster. Finally, we derive the cluster initial mass by computing the mass
loss experienced by the cluster during its lifetime, and adopting the various
estimates of the actual mass.
