Star formation in IC1396: Kinematics and subcluster structure revealed by Gaia

Aims. We investigate the star formation history of the IC1396 region by studying its kinematics and completing the population census. Methods. We used multiwavelength data, combining optical spectroscopy to identify and classify new members and near-infrared photometry to trace shocks, jets, and outflows as well as the interactions between the cluster members and the cloud. We also used Gaia EDR3 data to identify new potential members in the multidimensional proper motion and parallax space. Results. The revised Gaia EDR3 distance is 925±73 pc, slightly closer than previously obtained with DR2. The Gaia data reveal four distinct subclusters in the region. These subclusters are consistent in distance but display differences in proper motion. This result, with their age differences, hints toward a complex and varied star formation history. The Gaia data also unveil intermediate-mass objects that tend to evade spectroscopic and disk surveys. Our analysis has allowed us to identify 334 new members. We estimate an average age of ~4 Myr, confirming previous age estimates. With the new members added to our study, we estimate a disk fraction of 28%, lower than previous values, due to our method detecting mainly new, diskless, intermediate-mass stars. We find age differences between the subclusters, which offers evidence of a complex star formation history with different episodes of star formation.