Morphology and kinematics of the Cepheus Bubble

We investigate the spatial and velocity distribution of atomic hydrogen associated with the Cepheus Bubble, a giant (≈ 10◦ in angular diameter) dust ring around the Cep OB2 association. HI 21 cm data, taken from the Leiden/Dwingeloo survey, reveal HI structures in the [−14,+2] kms−1 velocity range which can be associated with prominent parts of the dust ring. In the same area the HI maps also show an expanding shell with a well-defined approaching side at VLSR = −37 kms−1 and a less well-defined receding side at VLSR ≈ −4 kms−1. The kinematics and size of this shell are best modelled by a supernova explosion, occurring in Cep OB2a at about 1.7 Myrs ago. Since the ages of several parts of the Cepheus Bubble are considerably higher than the age of the expanding shell, the supernova probably exploded in a pre-existing cavity, and its shock front might have interacted with the already existing star forming regions Sh2-140, IC 1396, and NGC 7129, leading to a new wave of star formation there.