From main-sequence binary to blast: MESA modeling of the double-detonation progenitor PTF1 J2238+7430

Context. Hot subdwarf B (sdB) stars in close binaries with white dwarf (WD) companions are potential progenitors of double-detonation thermonuclear supernovae. The recently discovered system PTF1 J2238+7430 is a candidate for this evolutionary channel, as it hosts a low-mass sdB and a comparatively massive white dwarf in a compact orbit. Aims. We aim to reproduce the evolutionary history of PTF1 J2238+7430, in which the sdB forms first through stable mass transfer, followed by the formation of the white dwarf through a subsequent common-envelope (CE) phase. Additionally, we seek to constrain the range of initial binary parameters that can lead to such double-detonation progenitors. Methods. Using the Modules for Experiments in Stellar Astrophysics (MESA), we performed detailed binary evolution simulations from the zero-age main sequence to the present-day configuration. We explored initial stellar masses, orbital periods, and mass-loss fractions, including the effects of angular momentum transfer, tidal synchronization, and gravitational-wave-driven orbital evolution. We derived the post-common envelope binary properties using the standard energy formalism during common envelope evolution. Results. Our models successfully reproduce the observed properties of PTF1 J2238+7430: a 0.406 M⊙ sdB and a 0.72 M⊙ white dwarf in a 76.34-minute orbit. Stable Roche-lobe overflow of an ∼2.7 M⊙ donor produces the sdB, while the white dwarf forms from the initially less massive companion during an episode of common envelope evolution. We find that the common envelope ejection efficiency must be high (αCE ≈ 0.87) to match the observed orbit, exceeding the canonical values for similar systems. We further delineate the allowed parameter space for initial binaries that can evolve into sdB+WD systems consistent with double-detonation progenitors. These limits are preliminary; a systematic exploration of all parameters is needed to obtain robust constraints. We highlight the main challenges in our MESA simulations and provide a useful starting point for future work. Conclusions. Our findings identify promising regions of parameter space for the formation of PTF1 J2238+7430–like systems and provide a foundation for future systematic studies of sdB+WD binaries as potential double-detonation Type Ia supernova progenitors.