  COIN-Gaia 13 is a newly discovered open cluster revealed by Gaia DR2 data. It
is a nearby open cluster with a distance of about 513 pc. Combined with the
five-dimensional astrometric data of Gaia EDR3 with higher accuracy, we use the
membership assignment algorithm (pyUPMASK) to determine the membership of
COIN-Gaia 13 in a large extended spatial region. The cluster has found 478
candidate members. After obtaining reliable cluster members, we further study
its basic properties and spatial distribution. Our results show that there is
an obvious extended structure of the cluster in the X-Y plane. This elongated
structure is distributed along the spiral arm, and the whole length is about
270 pc. The cluster age is 250 Myr, the total mass is about 439 M$_\odot$, and
the tidal radius of the cluster is about 11 pc. Since more than half of the
member stars (352 stars) are located outside twice the tidal radius, it is
suspected that this cluster is undergoing the dynamic dissolution process.
Furthermore, the spatial distribution and kinematic analysis indicate that the
extended structure in COIN-Gaia 13 is more likely to be caused by the
differential rotation of the Galaxy.
