  Magnetic flux ropes (MFRs) are believed to be at the heart of solar coronal
mass ejections (CMEs). A well-known example is the prominence cavity in the low
corona that sometimes makes up a three-part white-light (WL) CME upon its
eruption. Such a system, which is usually observed in quiet-Sun regions, has
long been suggested to be the manifestation of an MFR with relatively cool
filament material collecting near its bottom. However, observational evidence
of eruptive, filament-hosting MFR systems has been elusive for those
originating in active regions. By utilizing multi-passband extreme-ultra-violet
(EUV) observations from SDO/AIA, we present direct evidence of an eruptive MFR
in the low corona that exhibits a hot envelope and a cooler core; the latter is
likely the upper part of a filament that undergoes a partial eruption, which is
later observed in the upper corona as the coiled kernel of a fast, WL CME. This
MFR-like structure exists more than one hour prior to its eruption, and
displays successive stages of dynamical evolution, in which both ideal and
non-ideal physical processes may be involved. The timing of the MFR kinematics
is found to be well correlated with the energy release of the associated
long-duration C1.9 flare. We suggest that the long-duration flare is the result
of prolonged energy release associated with the vertical current sheet induced
by the erupting MFR.
