  Context. Prominence eruptions provide key observations to understand the
launch of coronal mass ejections as their cold plasma traces a part of the
unstable magnetic configuration.
  Aims. We select a well observed case to derive observational constraints for
eruption models.
  Methods. We analyze the prominence eruption and loop expansion and
contraction observed on 02 March 2015 associated with a GOES M3.7 class flare
(SOL2015-03-02T15:27) using the data from Atmospheric Imaging Assembly (AIA)
and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We study
the prominence eruption and the evolution of loops using the time-distance
techniques.
  Results. The source region is a decaying bipolar active region where magnetic
flux cancellation is present for several days before the eruption. AIA
observations locate the erupting prominence within a flux rope viewed along its
local axis direction. We identify and quantify the motion of loops in
contraction and expansion located on the side of the erupting flux rope.
Finally, RHESSI hard X-ray observations identify the loop top and two
foot-point sources.
  Conclusions. Both AIA and RHESSI observations support the standard model of
eruptive flares. The contraction occurs 19 minutes after the start of the
prominence eruption indicating that this contraction is not associated with the
eruption driver. Rather, this prominence eruption is compatible with an
unstable flux rope where the contraction and expansion of the lateral loop is
the consequence of a side vortex developing after the flux rope is launched.
