# Lambda Leonis

Lambda Leonis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Leo
Right ascension 09h 31m 43.22754s[1]
Declination +22° 58′ 04.6904″[1]
4.32[2]
Characteristics
Spectral type K4.5 III[3]
U−B color index +1.82[2]
B−V color index +1.54[2]
Astrometry
Proper motion (μ) RA: −20.17[1] mas/yr
Dec.: −39.47[1] mas/yr
Parallax (π) 9.91 ± 0.18[1] mas
Distance 329 ± 6 ly
(101 ± 2 pc)
Details
Luminosity 472[6] L
Surface gravity (log g) 1.60[7] cgs
Temperature 3,900[7] K
Metallicity [Fe/H] −0.29[7] dex
Rotational velocity (v sin i) 8[8] km/s
Other designations
Alterf, λ Leo, Leo, HD 82308, HIP 46750, HR 3773, SAO 80885, BD+23° 2107[9]
Database references

Lambda Leonis (λ Leo, λ Leonis), also named Alterf,[10] is a star in the constellation Leo. This star, along with ξ Cnc, were the Persian Nahn, "the Nose", and the Coptic Piautos, "the Eye", both lunar asterisms.[11] The star is bright enough to be seen with the naked eye, having an apparent visual magnitude of 4.32[2] Based upon an annual parallax shift of 0.00991 arcseconds, it is located about 329 light years from the Sun. At that distance, the visual magnitude of the star is reduced by an interstellar absorption factor of 0.06 because of extinction.[4]

This is a K-type giant star with a stellar classification of K4.5 III.[3] It is a suspected variable star with a reported magnitude range of 4.28−4.34.[12] The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 4.12±0.05 mas,[13] which, at its estimated distance, equates to a physical radius of nearly 45 times the radius of the Sun.[5] It shines with around 472 times the luminosity of the Sun,[6] from an outer atmosphere that has an effective temperature of 3,900 K.[7]

## Nomenclature

λ Leonis (Latinised to Lambda Leonis) is the star's Bayer designation.

It bore the traditional name Alterf, from the Arabic الطرف aṭ-ṭarf "the view (of the lion)". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN approved the name Alterf for this star on February 1st, 2017 and it is now so entered in the IAU Catalog of Star Names.[10]

## References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:, doi:10.1051/0004-6361:20078357.
2. ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
3. ^ a b 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. ^ a b Famaey, B.; et al. (2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430: 165–186, Bibcode:2005A&A...430..165F, arXiv:, doi:10.1051/0004-6361:20041272.
5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
{\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(101\cdot 4.12\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 89.5\cdot R_{\bigodot }\end{aligned}}}
6. ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, Bibcode:2012MNRAS.427..343M, arXiv:, doi:10.1111/j.1365-2966.2012.21873.x.
7. ^ a b c d McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
8. ^ Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B.
9. ^ "lam Leo -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-09-27.
10. ^ a b
11. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 114. ISBN 0-486-21079-0. Retrieved 2010-12-12.
12. ^ Kazarovets, E. V.; et al. (December 1998), New Catalogue of Suspected Variable Stars. Supplement, 1.0, 4655, Information Bulletin on Variable Stars, p. 1, Bibcode:1998IBVS.4655....1K.
13. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
14. ^ "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-04-01.