A Multi-Wavelength Study of the Segue 3 Cluster
  We present new SDSS and Washington photometry of the young, outer-halo
stellar system, Segue 3. Combined with archival VI-observations, our most
consistent results yield: $Z=0.006$, $\log(Age)=9.42$, $(m-M)_0=17.35$,
$E(B-V)=0.09$, with a high binary fraction of $0.39\pm 0.05$, using the Padova
models. We confirm that mass segregation has occurred, supporting the
hypothesis that this cluster is being tidally disrupted. A 3-parameter King
model yields a cluster radius of $r_{cl}=0.017^\circ$, a core radius of
$r_{c}=0.003^\circ$, and a tidal radius of $r_t=0.04^\circ \pm 0.02^\circ$. A
comparison of Padova and Dartmouth model-grids indicates that the cluster is
not significantly $\alpha$-enhanced, with a mean [Fe/H]$=-0.55^{+0.15}_{-0.12}$
dex, and a population age of only $2.6\pm 0.4$ Gyr. We rule out a
statistically-significant age spread at the main sequence turnoff because of a
narrow subgiant branch, and discuss the role of stellar rotation and cluster
age, using Dartmouth and Geneva models: approximately 70% of the Seg 3 stars at
or below the main sequence turnoff have enhanced rotation. Our results for
Segue 3 indicate that it is younger and more metal-rich than all previous
studies have reported to-date. From colors involving Washington-C and SDSS-u
filters, we identify several giants and a possible blue-straggler for future
follow-up spectroscopic studies, and we produce spectral energy distributions
of previously known members and potential Segue 3 sources with Washington
($CT_1$), Sloan (ugri), and VI-filters. Segue 3 shares the characteristics of
unusual stellar systems which have likely been stripped from external dwarf
galaxies as they are being accreted by the Milky Way, or that have been formed
during such an event. Its youth, metallicity, and location are all inconsistent
with Segue 3 being a cluster native to the Milky Way.
