Lambda Leonis

Lambda Leonis (λ Leonis, abbreviated Lam Leo, λ Leo), formally named Alterf /ælˈtərf/,[11][12] is a star in the constellation of Leo. 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.

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]
Apparent magnitude (V) 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
Radial velocity (Rv)24.27±0.19[4] km/s
Proper motion (μ) RA: −20.17[1] mas/yr
Dec.: −39.47[1] mas/yr
Parallax (π)9.91 ± 0.18[1] mas
Distance329 ± 6 ly
(101 ± 2 pc)
Absolute magnitude (MV)−0.70[5]
Details
Radius45[6] R☉
Luminosity472[7] L☉
Surface gravity (log g)1.60[8] cgs
Temperature3,900[8] K
Metallicity [Fe/H]−0.29[8] dex
Rotational velocity (v sin i)8[9] km/s
Other designations
Alterf, λ Leo, 4 Leo, BD+23°2107, HD 82308, HIP 46750, HR 3773, SAO 80885[10]
Database references
SIMBADdata

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 (IAU) organized a Working Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN approved the name Alterf for this star on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.[12]

This star, along with Xi Cancri, were the Persian Nahn, "the Nose", and the Coptic Piautos, "the Eye", both lunar asterisms.[14]

Properties

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.[15] The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 4.12±0.05 mas,[16] which, at its estimated distance, equates to a physical radius of nearly 45 times the radius of the Sun.[6] It shines with around 472 times the luminosity of the Sun,[7] from an outer atmosphere that has an effective temperature of 3,900 K.[8]

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gollark: If you're storing all the energy anyway then the hydrogen is just a pointless wasteful layer of indirection.
gollark: It isn't really a thing in much of Europe.
gollark: I don't believe this is accurate unless you have really cheap panels somehow. Or it's very sunny.
gollark: Although we don't have access to some counterfactual world where it didn't happen to check.

References
  1. van Leeuwen, F. (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.
  2. Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
  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. 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, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
  5. 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.
  6. 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:
  7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  8. 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.
  9. 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.
  10. "* lam Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-27.
  11. Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  12. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  13. "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-04-01.
  14. 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.
  15. 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.
  16. 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.
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