A and F spectral type runaway star candidates in the 30 Doradus region

The relative proper motions of eight A-F type runaway candidate stars, from the eleven cataloged stars by Platais et al. (2018) in the 30 Doradus (30 Dor) region of the Large Magellanic Cloud (LMC), are investigated using Gaia DR3 data. We cross-matched the coordinates presented by the authors with Gaia DR3 coordinates, and we took only eight stars that match Gaia DR3 coordinates within a 0.01 arcsec radius. From the relative proper motions of the target stars with respect to the field stars and the distance to 30 Dor, we estimated the relative tangential velocities of our target stars. We use the astrometric excess noise information to filter the field stars from star like objects, such as unresolved binaries. To eliminate foreground contamination of the field stars used to figure out the relative proper motions of the target stars, we made a parallax cut and a Color Magnitude Diagram (CMD) cut.Three stars, ID 204988, ID 271782, and ID 358858, are fast runaways, and two stars, ID 325244 and ID 373715, are slow runaways in the tangential plane of the 30 Dor region with relative proper motions of mu <= 3.92 mas yr1 with respect to their neighbors and mu <= 4.05 mas yr1 with respect to the central cluster R136, which correspond to a tangential velocity of 920.58 km s-1, and 951.30 km s-1, respectively. The remaining three sources ID 223800, ID 346142, and ID 371614, could be unresolved binaries because their astrometric excess noise values are different from zero and need further study to decide. The flight times of the target stars to the young, massive cluster R136 (kinematic ages) are calculated using angular separations from the cluster and their relative proper motions with respect to the cluster.Based on the calculated values of the flight time and relative proper motions, the stars ID 204988, ID 325244, ID 358858, and ID 373715 have proper motions and positions consistent with the runaway scenario from R136. The stars ID 204988, ID 325244, and ID 373715 have flight times from R136 agreed with ejection from the cluster more or less during the last half of the age of the cluster, whereas the star ID 358858 has flight times from R136 agree with ejection from the cluster during or shortly after the cluster is formed. The origin of the remaining one star, ID 271782, could not be R136 as it has a direction of motion different from the runaway scenario from R136, although its flight time to R136 agreed with ejection from the cluster.

Automated summary

This study investigates the relative proper motions of eight A-F type runaway candidate stars in the 30 Dor region of the Large Magellanic Cloud using Gaia DR3 data. The results show that five stars are runaway stars in the tangential plane of the 30 Dor region, and the remaining three stars may be unresolved binaries.