Searching for OB-type pre-supernova binary companions inside supernova remnants

We searched for OB-runaway stars inside supernova remnants (SNRs) as a pre-supernova binary companion. As the majority of massive stars are found in close binary systems, a runaway star ejected by the orbital energy after the supernova (SN) is expected to be found. Considering a binary mass fraction, q = 0.25-1.0, the runaway star is likely to have an OB spectral type. We selected 12 SNRs at Galactic longitudes 109°-189°. Using Gaia astrometry, we selected stars having consistent distances with those of the SNRs and showing a peculiar proper motion directed away from the central region of the SNRs. We also determined the radial distribution of the extinction towards the SNRs and estimated the spectral types of the OB-runaway candidates through Gaia and Two Micron All Sky Survey photometry. We found two candidates among 12 SNRs. By spectroscopic observations, Gaia DR3 195632152560621440 inside SNR G166.0 + 4.3 was found to be an evolved A3 type star that cannot be the pre-SN binary companion to the progenitor. Gaia DR3 513927750767375872 inside SNR HB 3 is the only OB-runaway candidate (2D space velocity of 33.3 ± 3.3 km s^-1). Based on photometric study, the star can be an early B-type main-sequence star with a slightly higher extinction relative to the SNR; however, it might instead be an evolved A-type star at the same distance. The other 11 SNRs do not host an OB-runaway star within their central regions. Although the runaway search was performed in a large interval of distance and extinction, we also estimated distances to the SNRs.