39 Leonis

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39 Leonis
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 10h 17m 14.53796s[1]
Declination +23° 06′ 22.3876″[1]
Apparent magnitude (V) 5.81[2]/11.40[3]
Spectral type F6 V[4] + M1[3]
U−B color index –0.05[5]
B−V color index +0.50[5]
Radial velocity (Rv) +37.4[6] km/s
Proper motion (μ) RA: –414.15[1] mas/yr
Dec.: –97.66[1] mas/yr
Parallax (π) 43.85 ± 0.36[1] mas
Distance 74.4 ± 0.6 ly
(22.8 ± 0.2 pc)
39 Tau A
Mass 0.98[7] M
Radius 0.99[8] R
Luminosity 2.19[7] L
Surface gravity (log g) 4.29 ± 0.14[2] cgs
Temperature 6,118 ± 49[2] K
Metallicity [Fe/H] –0.27[2] dex
Rotational velocity (v sin i) 2.16[9] km/s
Age 6.3[2] Gyr
39 Tau B
Radius 0.48[8] R
Surface gravity (log g) 4.83 ± 0.05[3] cgs
Temperature 3,740 ± 40[3] K
Metallicity [Fe/H] −0.33 ± 0.06[3] dex
Other designations
39 Leo, BD+23 2207, GJ 387, HD 89125, HIP 50384, HR 4039, SAO 81270.[10]

39 Leonis is the Flamsteed designation for a star in the zodiac constellation of Leo. It has an apparent visual magnitude of 5.90, so, according to the Bortle scale, it is faintly visible from suburban skies at night. Measurements made with the Hipparcos spacecraft show an annual parallax shift of 0.04385″,[1] which is equivalent to a distance of around 74.4 ly (22.8 pc) from the Sun.

The stellar classification of 39 Leonis is F6 V,[4] indicating it is a main sequence star. It shines with a luminosity more than double that of the Sun, although it has nearly the same mass and size.[7][8] This is a mature star with an estimated age of 6.3 billion years. The abundance of elements other than hydrogen and helium is about half that in the Sun, making this a metal-poor star.[7] The effective temperature of the stellar atmosphere is 6,118 K,[2] giving it the yellow-white hued glow of an F-type star.[11]

Observations made with the Akari satellite at a wavelength of 18 μm show an excess of infrared emission. This suggests the presence of an inner debris disk orbiting the star at a distance greater than four astronomical units (AU). There was no significant excess found at 22 μm.[7]

A companion star is located at an angular separation of 7.72″ along a position angle of 302.7°—this corresponds to a projected separation of 175 AU.[12] It is a red dwarf star with a classification of M1 and an apparent visual magnitude of 11.40.[3]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f Maldonado, J.; et al. (May 2012). "Metallicity of solar-type stars with debris discs and planets". Astronomy & Astrophysics. 541: A40. arXiv:1202.5884Freely accessible. Bibcode:2012A&A...541A..40M. doi:10.1051/0004-6361/201218800. 
  3. ^ a b c d e f Woolf, Vincent M.; Wallerstein, George (February 2006), "Calibrating M Dwarf Metallicities Using Molecular Indices", The Publications of the Astronomical Society of the Pacific, 118 (840): 218–226, arXiv:astro-ph/0510148Freely accessible, Bibcode:2006PASP..118..218W, doi:10.1086/498459. 
  4. ^ a b Phillips, N. M.; et al. (April 2010), "Target selection for the SUNS and DEBRIS surveys for debris discs in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 403 (3): 1089–1101, arXiv:0911.3426Freely accessible, Bibcode:2010MNRAS.403.1089P, doi:10.1111/j.1365-2966.2009.15641.x. 
  5. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J. 
  6. ^ Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14,000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198Freely accessible, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959. 
  7. ^ a b c d e Fujiwara, H.; et al. (February 2013), "AKARI/IRC 18 μm survey of warm debris disks", Astronomy and Astrophysics, 550: A15, arXiv:1211.6365Freely accessible, Bibcode:2013A&A...550A..45F, doi:10.1051/0004-6361/201219841. 
  8. ^ a b c Pasinetti-Fracassini, L. E.; et al. (February 2001), "Catalogue of Stellar Diameters (CADARS)", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289Freely accessible, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451. 
  9. ^ Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391Freely accessible, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725. 
  10. ^ "LTT 12754 -- High proper-motion Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2013-10-13. 
  11. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, retrieved 2012-01-16. 
  12. ^ Zapatero Osorio, M. R.; Martín, E. L. (May 2004), "A CCD imaging search for wide metal-poor binaries", Astronomy and Astrophysics, 419: 167–180, arXiv:astro-ph/0402310Freely accessible, Bibcode:2004A&A...419..167Z, doi:10.1051/0004-6361:20035907. 

Coordinates: Sky map 10h 17m 14.54s, +23° 06′ 22.39″