20 Leonis Minoris

20 Leonis Minoris is a binary star system in the northern constellation of Leo Minor. It is faintly visible to the naked eye, having an apparent visual magnitude of +5.4.[2] Based upon an annual parallax shift of 66.46 mas, it is located 49 light years from the Sun. The star has a relatively high proper motion[3] and is moving away from the Sun with a radial velocity of +56 km/s.[6] The system made its closest approach about 150,000 years ago when it came within 32.2 ly (9.86 pc).[13]

20 Leonis Minoris
Observation data
Epoch J2000      Equinox J2000
Constellation Leo Minor
Right ascension 10h 01m 00.65765s[1]
Declination +31° 55′ 25.2151″[1]
Apparent magnitude (V) +5.40[2]
Characteristics
Spectral type G3 Va Hδ1[3] + M7 V[4]
U−B color index +0.27[5]
B−V color index +0.65[5]
Astrometry
Radial velocity (Rv)+55.96±0.09[6] km/s
Proper motion (μ) RA: −527.63±0.30[1] mas/yr
Dec.: −429.42±0.18[1] mas/yr
Parallax (π)66.46 ± 0.32[1] mas
Distance49.1 ± 0.2 ly
(15.05 ± 0.07 pc)
Absolute magnitude (MV)4.46[7]
Details
20 LMi A
Mass1.12[8] M☉
Radius1.247±0.021[9] R☉
Luminosity1.378±0.027[9] L☉
Temperature5,735±5.6[10] K
Rotation10.64±0.14 d[2]
Age6.2–7.7[11] Gyr
20 LMi B
Mass0.11[8] M☉
Rotation19.2687 d[4]
Other designations
20 LMi, BD+32° 1964, FK5 1258, GJ 376, HD 86728, HIP 49081, HR 3951, SAO 61808, LHS 2216, LTT 12671[12]
Database references
SIMBADdata

The primary member of this system is a G-type main-sequence star with a stellar classification of G3 Va Hδ1.[3] It has 12% more mass and a 25% larger radius than the Sun. The star is about seven[11] billion years old and is spinning with a rotation period of 10.6 days.[2] The small companion is an active red dwarf star that has a relatively high metallicity.[14] The two stars are currently separated by 14.5 arc seconds, corresponding to a projected separation of 2016 AU.[8]

In 2020, a candidate exoplanet was detected orbiting 20 Leonis Minoris (HD 86728). With a minimum mass of 0.032 MJ (10.2 M⊕) and an orbital period of 31 days, this would most likely be a hot Neptune.[15]

The 20 Leonis Minoris planetary system[15]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) ≥0.032+0.005
−0.005 MJ		 0.2003+0.00007
−0.00007		 31.15+0.02
−0.02		 0.2+0.2
−0.1		 — —

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600, retrieved 2009-12-18.
  2. Hempelmann, A.; et al. (February 2016), "Measuring rotation periods of solar-like stars using TIGRE. A study of periodic CaII H+K S-index variability", Astronomy & Astrophysics, 586: 19, Bibcode:2016A&A...586A..14H, doi:10.1051/0004-6361/201526972, A14.
  3. Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. West, Andrew A.; et al. (October 2015), "An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-Type M Dwarfs", The Astrophysical Journal, 812 (1): 12, arXiv:1509.01590, Bibcode:2015ApJ...812....3W, doi:10.1088/0004-637X/812/1/3, S2CID 17434970, 3.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  7. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
  8. Tokovinin, A.; Kiyaeva, O. (February 2016), "Eccentricity distribution of wide binaries", Monthly Notices of the Royal Astronomical Society, 456 (2): 2070−2079, arXiv:1512.00278, Bibcode:2016MNRAS.456.2070T, doi:10.1093/mnras/stv2825, S2CID 1615080.
  9. Boyajian, Tabetha S.; et al. (February 2012), "Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars", The Astrophysical Journal, 746 (1): 101, arXiv:1112.3316, Bibcode:2012ApJ...746..101B, doi:10.1088/0004-637X/746/1/101, S2CID 18993744. See Table 10.
  10. Kovtyukh; Soubiran, C.; Belik, S. I.; Gorlova, N. I. (2003), "High precision effective temperatures for 181 F-K dwarfs from line-depth ratios", Astronomy and Astrophysics, 411 (3): 559–564, arXiv:astro-ph/0308429, Bibcode:2003A&A...411..559K, doi:10.1051/0004-6361:20031378, S2CID 18478960
  11. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785, S2CID 27151456
  12. "HD 86728". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-07-31.
  13. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, S2CID 59039482, A35.
  14. Gizis, J. E.; et al. (2000), "Two Nearby M Dwarf Binaries from 2MASS", Monthly Notices of the Royal Astronomical Society, 311 (2): 385, Bibcode:2000MNRAS.311..385G, doi:10.1046/j.1365-8711.2000.03060.x
  15. Hirsch, Lea A.; et al. (December 2020), "Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc", The Astronomical Journal, arXiv:2012.09190, Bibcode:2020arXiv201209190H.
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