IRAM and Gaia views of multi-episodic star formation in IC1396A: The
  origin and dynamics of the Class 0 protostar at the edge of an HII region
  (Abridged) IC1396A is a cometary globule containing the Class 0 source
IC1396A-PACS-1. We use IRAM 30m and Gaia DR2 data to explore the star-formation
history of IC1396A and investigate the possibilities of triggered star
formation. IRAM and Herschel continuum data reveal dust temperatures and column
densities. Heterodyne data reveal the velocity structure of the gas. Gaia DR2
proper motions for the stars complete the kinematics of the region.
IC1396A-PACS-1 shows molecular emission similar to a hot corino with warm
carbon chain chemistry, and is surrounded by gas at velocities significantly
different from the velocities of the Tr37 cluster. Combining the velocity,
column density, and temperature information and Gaia DR2 kinematics, we confirm
that IC1396A has suffered various episodes of star formation. IC1396A-PACS-1 is
probably the last intermediate-mass protostar that will form within IC1396A,
showing evidence of triggering by radiative driven implosion. Chemical
signatures place IC1396A-PACS-1 among the youngest protostars known. Gaia DR2
data reveal velocities in the plane of the sky $\sim$4km/s for IC1396A with
respect to Tr37. The total velocity difference (8 km/s) between the Tr37
cluster and IC1396A is too small for IC1396A to have undergone substantial
rocket acceleration, which imposes constraints on the distance to the ionizing
source in time and the possibilities of triggered star formation. The three
stellar populations in the globule reveal that objects located within
relatively close distances ($<$0.5pc) can be formed in various episodes within
a $\sim$1-2 Myr period. We expect substantial differences in initial conditions
for the resulting objects and their protoplanetary disks, which may affect
their evolution. Finally, evidence for short-range feedback from the embedded
protostars and, in particular, the A-type star V390 Cep is also observed.
