Lambda Pyxidis

Lambda Pyxidis (λ Pyxidis) is a yellow-hued star in the southern constellation of Pyxis. It is visible to the naked eye, having an apparent visual magnitude of 4.68.[2] Based upon an annual parallax shift of 16.98 mas as seen from Earth,[1] it is located around 192 light years from the Sun.

Lambda Pyxidis
Location of λ Pyxidis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Pyxis
Right ascension  09h 23m 12.25099s[1]
Declination −28° 50′ 01.9420″[1]
Apparent magnitude (V) 4.68[2]
Characteristics
Spectral type G8.5 IIIb Fe−1[3]
U−B color index +0.63[2]
B−V color index +0.91[2]
Astrometry
Radial velocity (Rv)+10.2[4] km/s
Proper motion (μ) RA: −128.25[1] mas/yr
Dec.: +20.70[1] mas/yr
Parallax (π)16.98 ± 0.24[1] mas
Distance192 ± 3 ly
(58.9 ± 0.8 pc)
Absolute magnitude (MV)+1.14[5]
Details
Mass2.06[4] M☉
Luminosity49[4] L☉
Surface gravity (log g)3.04±0.06[6] cgs
Temperature5,126±22[6] K
Metallicity [Fe/H]−0.05±0.02[6] dex
Rotational velocity (v sin i)4.4±0.2[7] km/s
Age1.3[4] Gyr
Other designations
λ Pyx, CPD−28° 3717, FK5 2747, HD 81169, HIP 46026, HR 3733, SAO 177374[8]
Database references
SIMBADdata

Measurements of changes in the star's proper motion over time indicate this is an astrometric binary system. The visible component is an evolved G-type giant star with a stellar classification of G8.5 IIIb Fe−1[3] and a spectrum that displays an underabundance of iron with weak cyanogen lines.[9] It is a red clump star that is generating energy through the fusion of helium at its core.[10]

Lambda Pyxidis has double the mass of the Sun and is an estimated 1.3 billion years old.[4] It is radiating 49[4] times the Sun's luminosity from its photosphere at an effective temperature of 5,126 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.
  2. 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.
  3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88.
  5. Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724.
  6. Alves, S.; et al. (April 2015), "Determination of the spectroscopic stellar parameters for 257 field giant stars", Monthly Notices of the Royal Astronomical Society, 448 (3): 2749–2765, arXiv:1503.02556, Bibcode:2015MNRAS.448.2749A, doi:10.1093/mnras/stv189.
  7. Ammler-von Eiff, M.; Reiners, A. (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: 31, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, A116.
  8. "lam Pyx". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-16.
  9. Luck, R. Earle (February 1991), "Chemical abundances for cyanogen-weak giants", Astrophysical Journal Supplement Series, 75: 579–610, Bibcode:1991ApJS...75..579L, doi:10.1086/191542
  10. Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278.
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