Lambda2 Fornacis

λ2 Fornacis, Latinized as Lambda2 Fornacis, is the primary of a binary star system in the southern constellation of Fornax. It is just visible to the naked eye as a dim, yellow-hued point of light with an apparent visual magnitude of 5.78[2] This body is located 83 light years distant from the Sun, based on stellar parallax,[1] and is drifting further away with a radial velocity of +12 km/s.[2]

For other stars with this Bayer designation, see λ Fornacis.
Lambda2 Fornacis

λ2 Fornacis on the right of the Fornax Dwarf Galaxy
Credit: ESO/Digitized Sky Survey 2
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Fornax
Right ascension 02h 36m 58.6079s[1]
Declination −34° 34′ 40.7135″[1]
Apparent magnitude (V) 5.78[2]
Characteristics
Spectral type G1V[3]
B−V color index +0.653±0.005[2]
Astrometry
Radial velocity (Rv)+11.80±0.65[2] km/s
Proper motion (μ) RA: −18.507±0.065[1] mas/yr
Dec.: −258.869±0.089[1] mas/yr
Parallax (π)39.3512 ± 0.0543[1] mas
Distance82.9 ± 0.1 ly
(25.41 ± 0.04 pc)
Absolute magnitude (MV)3.74±0.04[4]
Details
A
Mass1.18±0.04[4] M☉
Radius1.50±0.05[4] R☉
Luminosity3.03[2] L☉
Surface gravity (log g)4.12±0.03[4] cgs
Temperature5,936[4] K
Metallicity [Fe/H]+0.19[4] dex
Rotational velocity (v sin i)1.4 or 3.2[5] km/s
Age4.34±0.82[4] Gyr
B
Mass0.11[6] M☉
Other designations
λ2 For, CD–35°903, Gaia DR2 5062172841616745856, GC 3153, GJ 105.1, HD 16417, HIP 12186, HR 772, SAO 193811, PPM 278138, LTT 1280, NLTT 8516, GCRV 1481, 2MASS J02365859-3434404[7]
Database references
SIMBADdata
Exoplanet Archivedata
ARICNSdata
Extrasolar Planets
Encyclopaedia		data

This object is a G-type main-sequence star with a stellar classification of G1V.[3] It is considered a solar analog, being photometrically-similar to the Sun.[8] The star is an estimated 4.3[4] billion years old with 1.2 times the mass of the Sun and 1.5 times the Sun's radius.[4] It is radiating three[2] times the luminosity of the Sun from its photosphere at an effective temperature of 5,936 K.[4] The abundance of elements with more mass than helium is 55% higher than in the Sun.[4][9]

There is a faint co-moving companion star located to the east of the main star at an angular separation of 45″. This is most likely an M5–M6 class red dwarf with 0.11 times the Sun's mass. The projected separation between the pair is about 1,000 AU.[6]

Planetary system

Precision Doppler spectroscopy from an intensive 48 night observing campaign on the Anglo-Australian Telescope has revealed the presence of a low-mass extrasolar planet orbiting the star. This object has an orbital period of 17.24 days and an eccentricity of 0.2. It has a minimum (baseline) mass of 21.9 M⊕.[10]

The Lambda2 Fornacis planetary system[10]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥0.069±0.007 MJ 0.14±0.01 17.24±0.01 0.2±0.09 — —

See also
  • List of extrasolar planets

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  4. da Silva, L.; et al. (November 2006). "Basic physical parameters of a selected sample of evolved stars". Astronomy and Astrophysics. 458 (2): 609–623. arXiv:astro-ph/0608160. Bibcode:2006A&A...458..609D. doi:10.1051/0004-6361:20065105. S2CID 9341088.
  5. Soto, M. G.; Jenkins, J. S. (July 2018). "Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES). I. Code description and dwarf stars catalogue". Astronomy & Astrophysics. 615: 28. arXiv:1801.09698. Bibcode:2018A&A...615A..76S. doi:10.1051/0004-6361/201731533. A76.
  6. Mugrauer, M.; et al. (March 2014). "New wide stellar companions of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 439 (1): 1063–1070. Bibcode:2014MNRAS.439.1063M. doi:10.1093/mnras/stu044.
  7. "lam02 For". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-23.
  8. Datson, Juliet; et al. (February 2015). "Spectroscopic study of solar twins and analogues". Astronomy & Astrophysics. 574: 12. arXiv:1412.8168. Bibcode:2015A&A...574A.124D. doi:10.1051/0004-6361/201425000. S2CID 53708062. A124.
  9. 10+0.19 = 1.55
  10. O’Toole, Simon; et al. (2009). "A Neptune-mass Planet Orbiting the Nearby G Dwarf HD16417". The Astrophysical Journal. 697 (2): 1263–1268. arXiv:0902.4024. Bibcode:2009ApJ...697.1263O. doi:10.1088/0004-637X/697/2/1263. S2CID 16341718.

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