Characterizing low contrast Galactic open clusters with GAIA DR2
  In this study, we characterized 16 objects previously classified as faint or
low contrast Galactic open clusters (OCs). We employed parameters associated to
the OCs dynamical evolution: core ($r_c$), tidal ($r_t$) and half-mass
($r_{hm}$) radii, age and crossing time ($t_{cr}$). Relations among these
parameters were exploited to draw some evolutionary connections. We also
included 11 OCs with previous characterizations to provide wider coverage of
the parameters space. The investigated sample spans a considerable range in age
(log (t/yr) ~7.0 - 9.7) and Galactocentric distance ($R_G$ ~ 6 - 11 kpc). Most
of them present solar metallicity. We employed GAIA DR2 astrometry and
photometry and selected member stars through a decontamination algorithm which
explores the 3D astrometric space ($\mu_{\alpha}$, $\mu_{\delta}$, $\varpi$) to
assign membership likelihoods. Previous studies of most of these objects were
based mostly on photometric information. All investigated OCs were proved to be
real stellar concentrations and relations among their parameters indicate a
general disruption scenario in which OCs tend to be more concentrated as they
evolve. Internal interactions sucessively drive OCs to develop more dynamically
relaxed structures and make them less subject to mass loss due to tidal
effects. Tidal radius tends to increase with $R_G$ in accordance with the
strength of the Galactic tidal field. Besides, the correlation between the
$r_c$ and the dynamical ratio $\tau_{\textrm{dyn}}$ = age/$t_{cr}$ suggests two
distinct evolutionary sequences, which may be consequence of different initial
formation conditions.
