The EBLM Project XVIII. 3D Obliquities of Five Low-Mass Eclipsing Binaries
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2025
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| author | Spejcher, Becca Martin, David V. Pandina, Jake Zhang, Andy Ammons, Max Tubthong, Wata Triaud, Amaury Sethi, Ritika Vowell, Noah Barker, Adrian Maxted, Pierre Duck, Alison Summers, Shelby Bouchy, François Lendl, Monika Marmier, Maxime Megevand, Vincent Pepe, Francesco Tewes, Malte Udry, Stéphane |
| author_facet | Spejcher, Becca Martin, David V. Pandina, Jake Zhang, Andy Ammons, Max Tubthong, Wata Triaud, Amaury Sethi, Ritika Vowell, Noah Barker, Adrian Maxted, Pierre Duck, Alison Summers, Shelby Bouchy, François Lendl, Monika Marmier, Maxime Megevand, Vincent Pepe, Francesco Tewes, Malte Udry, Stéphane |
| contents | A question that continues to perplex astronomers is the formation of tight stellar binaries. There is too much angular momentum in a collapsing and fragmenting protostellar cloud to form a stellar binary in situ with a separation less than an AU, yet thousands of these short-period binaries have been discovered. One indication of a binary's formation is the angle between the stellar spin and orbital axes -- its obliquity. The classical method for determining projtected stellar obliquity is the Rossiter-McLaughlin effect. This method has been applied to over 100 hot Jupiters, yet only a handful of stellar binaries. Of the binary systems with measured projected obliquities, even fewer have measured 3D obliquities. In this paper, we add five more short-period binary 3D obliquity measurements to the sample that previously consisted of a single system. We present Rossiter-McLaughlin measurements for EBLM J0239-20, EBLM J0941-31, EBLM 1037-25, EBLM 1141-37, and EBLM J2025-45. These systems consist of an M-dwarf eclipsing an F/G type primary. We combined CORALIE and HARPS spectroscopy with TESS photometry of primary and secondary eclipses. We show that even though the sky-projected obliquities seem to be aligned, there is modest but non-zero spin-orbit misalignment ($ψ$ between 5 and 20$^{\circ}$). Our primary stars straddle the Kraft break at $\sim 6250K$. Finally, we derive the M-dwarf masses and radii to precisions better than 3\%. With the exception of EBLM J0941-31, each system has an inflated radius greater than $5σ$ from the expected radius from stellar models. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_23430 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The EBLM Project XVIII. 3D Obliquities of Five Low-Mass Eclipsing Binaries Spejcher, Becca Martin, David V. Pandina, Jake Zhang, Andy Ammons, Max Tubthong, Wata Triaud, Amaury Sethi, Ritika Vowell, Noah Barker, Adrian Maxted, Pierre Duck, Alison Summers, Shelby Bouchy, François Lendl, Monika Marmier, Maxime Megevand, Vincent Pepe, Francesco Tewes, Malte Udry, Stéphane Solar and Stellar Astrophysics Earth and Planetary Astrophysics A question that continues to perplex astronomers is the formation of tight stellar binaries. There is too much angular momentum in a collapsing and fragmenting protostellar cloud to form a stellar binary in situ with a separation less than an AU, yet thousands of these short-period binaries have been discovered. One indication of a binary's formation is the angle between the stellar spin and orbital axes -- its obliquity. The classical method for determining projtected stellar obliquity is the Rossiter-McLaughlin effect. This method has been applied to over 100 hot Jupiters, yet only a handful of stellar binaries. Of the binary systems with measured projected obliquities, even fewer have measured 3D obliquities. In this paper, we add five more short-period binary 3D obliquity measurements to the sample that previously consisted of a single system. We present Rossiter-McLaughlin measurements for EBLM J0239-20, EBLM J0941-31, EBLM 1037-25, EBLM 1141-37, and EBLM J2025-45. These systems consist of an M-dwarf eclipsing an F/G type primary. We combined CORALIE and HARPS spectroscopy with TESS photometry of primary and secondary eclipses. We show that even though the sky-projected obliquities seem to be aligned, there is modest but non-zero spin-orbit misalignment ($ψ$ between 5 and 20$^{\circ}$). Our primary stars straddle the Kraft break at $\sim 6250K$. Finally, we derive the M-dwarf masses and radii to precisions better than 3\%. With the exception of EBLM J0941-31, each system has an inflated radius greater than $5σ$ from the expected radius from stellar models. |
| title | The EBLM Project XVIII. 3D Obliquities of Five Low-Mass Eclipsing Binaries |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2511.23430 |