G 68-34: A Double-lined M-dwarf Eclipsing Binary in a Hierarchical Triple System
Abstract
Using high-resolution spectra from the Tillinghast Reflector Echelle Spectrograph and photometry from sector 56 of the Transiting Exoplanet Survey Satellite, we report that the nearby M dwarf G 68-34 is a double-lined eclipsing binary. The pair is spin-orbit synchronized with a period of 0.655 days. The light curve shows significant spot modulation with a larger photometric amplitude than that of the grazing eclipses. We perform a joint fit to the spectroscopic and photometric data, obtaining masses of 0.3280 ± 0.0034M ⊙ and 0.3207 ± 0.0036M ⊙ and radii of 0.345 ± 0.014R ⊙ and 0.342 ± 0.014R ⊙ after marginalizing over unknowns in the starspot distribution. This system adds to the small but growing population of fully convective M dwarfs with precisely measured masses and radii that can be used to test models of stellar structure. The pair also has a white-dwarf primary at 9″ separation, with the system known to be older than 5 Gyr from the white-dwarf cooling age. The binarity of G 68-34 confirms our hypothesis from Pass et al.: in that work, we noted that G 68-34 was both rapidly rotating and old, highly unusual given our understanding of the spin-down of M dwarfs, and that a close binary companion may be responsible.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2023
- DOI:
- 10.3847/1538-4357/accadf
- arXiv:
- arXiv:2304.02466
- Bibcode:
- 2023ApJ...949...37P
- Keywords:
-
- Eclipsing binary stars;
- Binary stars;
- M dwarf stars;
- Starspots;
- Stellar radii;
- Stellar masses;
- Spectroscopic binary stars;
- 444;
- 154;
- 982;
- 1572;
- 1626;
- 1614;
- 1557;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- Accepted for publication in ApJ, 10 pages, 5 figures, 3 tables