A New LISA-detectable Type Ia Supernova Progenitor in the Southern Sky: SMSS J1138−5139
We present the discovery and analysis of a nearby eclipsing ultracompact accreting binary 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}_{\mathrm{o...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/add1cf |
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| Summary: | We present the discovery and analysis of a nearby eclipsing ultracompact accreting binary 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 ${P}_{\mathrm{orb,RV}}=27.682\,\mathrm{minutes}$ , twice the photometric period seen in 2 minute cadence data from TESS Sector 37. We model our optical spectroscopy together with new simultaneous multiband time-series photometry from Gemini to place constraints on the binary parameters. Our light-curve modeling finds that SMSS J1138−5139 contains an M _2 = 0.25 ± 0.01 M _⊙ pre-white-dwarf donor with a massive M _1 = 1.02 ± 0.05 M _⊙ white dwarf accretor at orbital inclination $i=88\mathop{.}\limits^{\circ }6\pm 0\mathop{.}\limits^{\circ }1$ . 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 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 a signal-to-noise ratio of 7–10 after a 48 month mission. |
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| ISSN: | 1538-4357 |