| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10 18 35.137 |
| Declination | −11° 43′ 00.24″ |
| Apparent magnitude (V) | 13.07±0.015 |
| Characteristics | |
| Spectral type | M3.5 V + M5.0 V |
| Apparent magnitude (B) | 14.678 |
| Apparent magnitude (G) | 11.8465±0.0005 |
| Apparent magnitude (J) | 9.007±0.030 |
| Astrometry | |
| Proper motion (μ) | RA: −341.537 mas/yr Dec.: −247.747 mas/yr |
| Parallax (π) | 45.3972 ± 0.0301 mas |
| Distance | 71.85 ± 0.05 ly (22.03 ± 0.01 pc) |
| Absolute magnitude (MV) | 11.36±0.02 |
| Position (relative to LTT 3780) | |
| Component | LP 729-55 |
| Epoch of observation | J2015.5 |
| Angular distance | 15.81±0.150″ |
| Position angle | 96.9±0.2° |
| Projected separation | 348±3 AU |
| Details | |
| LTT 3780 | |
| Mass | 0.401±0.012 M☉ |
| Radius | 0.374±0.011 R☉ |
| Luminosity | 0.167±0.003 L☉ |
| Surface gravity (log g) | 4.896±0.029 cgs |
| Temperature | 3,331±157 K |
| Metallicity | 0.09±0.16 dex 0.28 −0.13 dex |
| Rotation | 104±15 |
| Rotational velocity (v sin i) | < 1.3 km/s |
| Age | 3.10+6.20 −0.98 Gyr |
| LP 729-55 | |
| Mass | 0.136±0.004 M☉ |
| Radius | 0.173±0.005 R☉ |
| Other designations | |
| G 162-44, LP 729-54, LTT 3780, NLTT 23974, 2MASS J10183516-1142599 | |
| Database references | |
| SIMBAD | data |
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, 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. The abundance of iron, an indicator of the star's metallicity, appears higher than in the Sun. The star is inactive, showing a negligible level of magnetic activity in its chromosphere. 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.
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. At this separation, the orbital period would be ~9,100 years. The fainter member is a red dwarf with a class of M5.0 V. It has 14% of the mass of the Sun and 17% of the Sun's radius.
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.
| 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
- ^ 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.
- ^ 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.
- ^ 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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