SIMBAD references

A large region (9°x9°) surrounding the OB association Cassiopeia OB7 has been studied for signs of interaction between the stars and the ambient gas. A large half-shell has been detected in H I around Cas OB7, as well as in the infrared and partially in CO. This half-shell covers a range of 20 km/s but could reach 40 km/s when extrapolating to the whole shell. The structure is 120 pc across if located at 2 kpc, the distance to Cas OB7. At this distance, we estimate the mass of the shell to be approximately 30,000 M_☉. Interestingly, all Cas OB7 members are located well within the edge of this shell. We believe that there is a strong hint of interaction between the gas and the stars based on morphological evidence. The velocity of both objects (association and shell) and their respective distance are also in agreement. We explain the missing half by an expansion into the interarm region.