On the nature of a shell of young stars in the outskirts of the Small
  Magellanic Cloud
  Understanding the evolutionary history of the Magellanic Clouds requires an
in-depth exploration and characterization of the stellar content in their outer
regions, which ultimately are key to tracing the epochs and nature of past
interactions. We present new deep images of a shell-like over-density of stars
in the outskirts of the Small Magellanic Cloud (SMC). The shell, also detected
in photographic plates dating back to the fifties, is located at ~1.9 degr from
the center of the SMC in the north-east direction.The structure and stellar
content of this feature were studied with multi-band, optical data from the
Survey of the MAgellanic Stellar History (SMASH) carried out with the Dark
Energy Camera on the Blanco Telescope at Cerro Tololo Inter-American
Observatory. We also investigate the kinematic of the stars in the shell using
the Gaia Data Release 2. The shell is composed of a young population with an
age ~ 150 Myr, with no contribution from an old population. Thus, it is hard to
explain its origin as the remnant of a tidally disrupted stellar system. The
spatial distribution of the young main-sequence stars shows a rich
sub-structure, with a spiral arm-like feature emanating from the main shell and
a separated small arc of young stars close to the globular cluster NGC 362. We
find that the absolute g-band magnitude of the shell is M_{g,shell} = -10.78+/-
0.02, with a surface brightness of mu_{g,shell} = 25.81+/- 0.01 mag/arcsec^{2}.
We have not found any evidence that this feature is of tidal origin or a bright
part of a spiral arm-like structure. Instead, we suggest that the shell formed
in a recent star formation event, likely triggered by an interaction with the
Large Magellanic Cloud and/or the Milky Way, ~150 Myr ago.
