LTT 3780, also known as TOI-732 or LP 729-54, is the brighter component of a wide visual binary star system in the constellation Hydra. This star is host to a pair of orbiting exoplanets. Based on parallax measurements, it is located at a distance of 72 light years from the Sun. LTT 3780 has an apparent visual magnitude of 13.07,[2] requiring a telescope to view.
The spectrum of LTT 3780 presents as a small M-type main-sequence star, a red dwarf, with a stellar classification of M3.5 V. It is spinning very slowly, with a rotation period of 104 days.[2] The abundance of iron, an indicator of the star's metallicity, appears higher than in the Sun.[3] The star is inactive, showing a negligible level of magnetic activity in its chromosphere.[2] It has about 40% of the mass and 37% of the radius of the Sun. The star is radiating just 17% of the Sun's luminosity from its photosphere at an effective temperature of 3,331.[2]
Collectively designated LDS 3977, the two stars in this system share a common proper motion and have an angular separation of 15.8″, which corresponds to a (physical) projected separation of 348 AU.[3] At this separation, the orbital period would be ~9,100 years.[2] The fainter member is a red dwarf with a class of M5.0 V.[3] It has 14% of the mass of the Sun and 17% of the Sun's radius.[2]
Planetary system
In 2020, an analysis carried out by a team of astronomers led by astronomer Ryan Cloutier of the TESS project confirmed the existence of two planets on mildly eccentric orbits, the inner being a super-Earth and the outer a small gas planet about half the mass of Uranus.
LTT 3780 c
Astronomers utilizing the Gemini South 8.1-meter telescope performed an atmospheric survey of LTT 3780 c through high-resolution transmission spectroscopy. From observations during a single transit, they detected tentative signs of methane in the atmosphere but found no traces of ammonia, even though it is highly detectable in a cloud-free, hydrogen-rich atmosphere.[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.34+0.24 −0.23 M🜨 |
0.01203+0.00054 −0.00053 |
0.77±0.001 | 0.064+0.075 −0.046 |
85.9° | 1.35±0.06 R🜨 |
| c | 6.29+0.63 −0.61 M🜨 |
0.0762±0.0034 | 12.252131+0.000072 −0.000064 |
0.115+0.07 −0.065 |
89.08° | 2.42±0.1 R🜨 |
See also
References
- ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d e f g h i j k l m n o p q r s t Cloutier, Ryan; et al. (2020). "A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780". The Astronomical Journal. 160 (1): 3. arXiv:2003.01136. Bibcode:2020AJ....160....3C. doi:10.3847/1538-3881/ab91c2. S2CID 211817805.
- ^ a b c d e f g h Nowak, G.; et al. (2020). "The CARMENES search for exoplanets around M dwarfs. Two planets on the opposite sides of the radius gap transiting the nearby M dwarf LP 729-54". Astronomy & Astrophysics. A173: 642. arXiv:2003.01140. Bibcode:2020A&A...642A.173N. doi:10.1051/0004-6361/202037867. S2CID 211818198.
- ^ Bonfanti, A.; et al. (2024). "Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley". Astronomy & Astrophysics. 682 A66. arXiv:2311.12577. Bibcode:2024A&A...682A..66B. doi:10.1051/0004-6361/202348180.
- ^ "LTT 3780". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-06.
- ^ Cabot, Samuel H. C.; et al. (2024-05-01). "High-resolution Spectroscopic Reconnaissance of a Temperate Sub-Neptune". The Astrophysical Journal Letters. 966 (1) L10. arXiv:2403.18891. Bibcode:2024ApJ...966L..10C. doi:10.3847/2041-8213/ad3828.
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