Lambda Leonis

Lambda Leonis (λ Leonis, abbreviated Lam Leo, λ Leo), formally named Alterf /ælˈtərf/,^[9][10] 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. At that distance, the visual magnitude of the star is reduced by an interstellar absorption factor of 0.06 because of extinction.^[4]

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 mas[1]
Distance	329 ± 6 ly (101 ± 2 pc)
Absolute magnitude (MV)	−0.70[5]
Details[6]
Mass	1.29±0.18 M☉
Radius	44.93+0.85 −0.87 R☉
Luminosity	541.4±33.5 L☉
Surface gravity (log g)	1.70 cgs
Temperature	4,152±53 K
Metallicity [Fe/H]	−0.21 dex
Rotational velocity (v sin i)	8[7] km/s
Age	3.62±1.37 Gyr
Other designations
Alterf, λ Leo, 4 Leo, BD+23°2107, HD 82308, HIP 46750, HR 3773, SAO 80885[8]
Database references
SIMBAD	data

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)".^{[citation needed]} In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN)^[11] 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.^[10]

This star, along with Xi Cancri, were the Persian Nahn, "the Nose", and the Coptic Piautos, "the Eye", both lunar asterisms.^[12]

Properties

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.^[13] Lambda Leonis is 29% more massive than the Sun and is 3.6 billion years old. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 4.143±0.025 mas, which, at its estimated distance, equates to a physical radius of nearly 45 times the radius of the Sun.^[6] It shines with around 540 times the luminosity of the Sun, from an outer atmosphere that has an effective temperature of 4,150 K.^[6]

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, S2CID 18759600.
2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, 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 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
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, S2CID 119257644.
6. Baines, Ellyn K.; et al. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1), 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
7. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B.
8. "* lam Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-27.{{cite web}}: CS1 maint: postscript (link)
9. 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.
10. "Naming Stars". IAU.org. Retrieved 16 December 2017.
11. "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-04-01.
12. 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.
13. Kazarovets, E. V.; et al. (December 1998), "New Catalogue of Suspected Variable Stars. Supplement", Information Bulletin on Variable Stars, 1.0, 4655: 1, Bibcode:1998IBVS.4655....1K.