Research Division Seminar
Runaway O and Be stars found using Gaia DR3, new stellar bow shocks and search for binaries

A relevant fraction of massive stars are runaways, moving with a significant peculiar velocity with respect to their environment. Kicks from supernova explosions in binary systems or the dynamical ejection of stars from clusters can account for the runaway genesis. We have used Gaia DR3 data to study the velocity distribution of massive O and Be stars from the GOSC and BeSS catalogs and identify runaway stars using a 2D-velocity method. We have discovered 42 new runaways from GOSC and 47 from BeSS, among a total of 106 and 69 runaways found within these catalogs, respectively. These numbers imply a percentage of runaways of ~25% for O-type stars ~5% for Be-type stars. The higher percentages and higher velocities found for O-type compared to Be-type runaways underline that the dynamical ejection scenario is more likely than the binary supernova explosion scenario. We have also performed multi-wavelength studies of our runaways. We have used WISE infrared images to discover new stellar bow shocks around the runaway stars. We have also conducted VLA radio observations of some of these bow shocks. Finally, our runaway stars include seven X-ray binaries and one gamma-ray binary, implying that new such systems could be found by conducting detailed multi-wavelength studies. In this talk I will report on this ongoing project to find new runaway stars, study their interaction with the ISM and search for high-energy binary systems.