2026ApJ...999..162C

The supernova remnant (SNR) S147 contains the pulsar PSR J0538+2817 and a likely unbound binary companion, HD 37424. It is the only good Galactic candidate for a binary unbound by a core-collapse supernova. Using Gaia DR3 parallaxes and photometry, we select the stars local to SNR S147 (${\varpi }_{S147}=0.7{3}_{-0.05}^{+0.04}\,\,\rm{mas}\,$) in a cylinder with a projected radius of 100 pc and a parallax range of 0.614 < ϖ < 0.787 mas (a length of ≃360 pc). We individually model the most luminous of these stars. The two most luminous single stars are the unbound binary companion, HD 37424, and HD 37367, with estimated masses of (13.51 ± 0.05) M_⊙ and (14.30 ± 0.09) M_⊙, respectively. The two most luminous binary systems are the spectroscopic binary HD 37366 and the eclipsing binary ET Tau, which have primary masses of (20.9 ± 0.12) and (16.7 ± 0.09) M_⊙, respectively. We model the Gaia color-magnitude diagram of this local stellar population using both single stars and a model consisting of noninteracting binaries using solar metallicity PARSEC v2.0 isochrones. For both models, the estimated age distributions of the 439 M_G < 0 mag stars favor a high-mass progenitor of 21.5-41.1 M_⊙ for the supernova.