Another Look at the EBS: A Stellar Debris Stream and a Possible
  Progenitor
  Using the Sloan Digital Sky Survey Data Release 7, we reexamine the Eastern
Banded Structure (EBS), a stellar debris stream first discovered in Data
Release 5 and more recently detected in velocity space by Schlaufman et al. The
visible portion of the stream is 18 degrees long, lying roughly in the Galactic
Anticenter direction and extending from Hydra to Cancer. At an estimated
distance of 9.7 kpc, the stream is approximately 170 pc across on the sky. The
curvature of the stream implies a fairly eccentric box orbit that passes close
to both the Galactic center and to the sun, making it dynamically distinct from
the nearby Monoceros, Anticenter, and GD-1 streams. Within the stream is a
relatively strong, 2 degree-wide concentration of stars with a very similar
color-magnitude distribution that we designate Hydra I. Given its prominence
within the stream and its unusual morphology, we suggest that Hydra I is the
last vestige of the EBS's progenitor, possibly already unbound or in the final
throes of tidal dissolution. Though both Hydra I and the EBS have a relatively
high velocity dispersion, given the comparatively narrow width of the stream
and the high frequency of encounters with the bulge and massive constituents of
the disk that such an eccentric orbit would entail, we suggest that the
progenitor was likely a globular cluster, and that both it and the stream have
undergone significant heating over time.
