2024/11/28 by Alekzander Kosakowski, Kosakowski, Alekzander, M. Dorsch +9 · 1 voice · 2 citations
Physics and Astronomy · Earth and Planetary Sciences · #Gamma-ray bursts and supernovae #Astrophysics and Cosmic Phenomena #Geophysics and Gravity Measurements
paper · pdf · doi:10.48550/arxiv.2411.19391
We present the discovery and analysis of a nearby eclipsing ultra-compact accreting binary at coordinates 11:38:10.91 -51:39:49.15 (SMSS J1138-5139), the first well-constrained LISA-detectable Type Ia supernova progenitor. Our time series optical spectroscopy identifies its orbital period through radial velocity monitoring at P\rm orb,RV=27.69±0.03~\rm min; twice the photometric period seen in 2-minute cadence data from TESS Sector 37. We model our optical spectroscopy together with new simultaneous multi-band time series photometry from Gemini to place constraints on the binary parameters. Our light curve modeling finds that SMSS J1138-5139 contains an M2=0.24~\rm M_\odot pre-white dwarf donor with a massive M1=0.99~\rm M_\odot white dwarf accretor at orbital inclination i=88.7~\rm deg. Based on our photometrically derived system parameters, we expect that gravitational wave radiation will drive SMSS J1138-5139 to a merger within τ=5.7±0.3~\rm Myr and result in a Type Ia supernova. Even without a direct merger event, the component masses of SMSS J1138-5139 and active hydrogen accretion suggest that eventual helium accretion will likely also trigger a Type Ia supernova explosion through the dynamically-driven double-degenerate double-detonation (D6) channel. We expect LISA to detect the gravitational wave emission from SMSS J1138-5139 with signal-to-noise 7-10 after a 48-month mission.