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LTT 3780

Coordinates: Sky map 10h 18m 35.137s, −11° 43′ 0.242″
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LTT 3780
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension 10h 18m 35.137s[1]
Declination −11° 43′ 00.24″[1]
Apparent magnitude (V) 13.07±0.015[2]
Characteristics
Spectral type M3.5 V + M5.0 V[3]
Apparent magnitude (B) 14.678
Apparent magnitude (G) 11.8465±0.0005[2]
Apparent magnitude (J) 9.007±0.030[2]
Astrometry
Proper motion (μ) RA: −341.537 mas/yr[1]
Dec.: −247.747 mas/yr[1]
Parallax (π)45.3972 ± 0.0301 mas[1]
Distance71.85 ± 0.05 ly
(22.03 ± 0.01 pc)
Absolute magnitude (MV)11.36±0.02[2]
Position (relative to LTT 3780)[3]
ComponentLP 729-55
Epoch of observationJ2015.5
Angular distance15.81±0.150
Position angle96.9±0.2°
Projected separation348±3 AU
Details
LTT 3780
Mass0.401±0.012[2] M
Radius0.374±0.011[2] R
Luminosity0.167±0.003[3] L
Surface gravity (log g)4.896±0.029[2] cgs
Temperature3,331±157[2] K
Metallicity [Fe/H]0.09±0.16 dex[3]
0.28+0.11
−0.13
[2] dex
Rotation104±15[2]
Rotational velocity (v sin i)< 1.3[2] km/s
Age3.10+6.20
−0.98
[4] Gyr
LP 729-55
Mass0.136±0.004[2] M
Radius0.173±0.005[2] R
Other designations
G 162-44, LP 729-54, LTT 3780, NLTT 23974, 2MASS J10183516-1142599[5]
Database references
SIMBADdata

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

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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

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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]

Size comparison of the two known planets of LTT 3780 (artistic concept) with Earth
The LTT 3780 planetary system[2][3]
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

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References

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  1. ^ 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ 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.
  5. ^ "LTT 3780". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-03-06.
  6. ^ 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.