Lambda² Tucanae

Lambda² Tucanae is a solitary[7] star in the southern constellation of Tucana. It is faintly visible to the naked eye with an apparent visual magnitude of +5.45.[2] Based upon an annual parallax shift of 14.6 mas as seen from Earth, it is located around 223 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.09 due to interstellar dust.[2]

This article is about Lambda² Tucanae. For other stars with this Bayer designation, see Lambda Tucanae.

Lambda² Tucanae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Tucana
Right ascension	00^h 55^m 00.31129^s[1]
Declination	−69° 31′ 37.5025″[1]
Apparent magnitude (V)	+5.45[2]
Characteristics
Spectral type	K2 III[3]
B−V color index	+1.10[2]
Astrometry
Radial velocity (Rv)	+5.1±2.8[4] km/s
Proper motion (μ)	RA: +6.842[1] mas/yr Dec.: −43.735[1] mas/yr
Parallax (π)	14.6214 ± 0.0817[1] mas
Distance	223 ± 1 ly (68.4 ± 0.4 pc)
Absolute magnitude (MV)	+1.29[5]
Details[2]
Mass	1.75 M☉
Radius	9.84+0.22 −0.42[1] R☉
Luminosity	39.2±0.3[1] L☉
Surface gravity (log g)	2.74 cgs
Temperature	4,605+101 −52[1] K
Metallicity [Fe/H]	−0.07±0.14 dex
Rotational velocity (v sin i)	3.14 km/s
Other designations
λ^2 Tuc, CD–70°40, FK5 34, HD 5457, HIP 4293, HR 270, SAO 248281[6]
Database references
SIMBAD	data

This is an orange-hued K-type giant star on the red giant branch,[2] with a stellar classification of K2 III.[3] It has an estimated 1.75[2] times the mass of the Sun but after evolving away from the main sequence it has expanded to 9.8 times the Sun's radius. The star is radiating 39 times the solar luminosity from its photosphere at an effective temperature of 4,605 K.[1]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Jones, M. I.; et al. (December 2011), "Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties", Astronomy & Astrophysics, 536: 7, arXiv:1110.6459, Bibcode:2011A&A...536A..71J, doi:10.1051/0004-6361/201117887, A71.
3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
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. "lam Tuc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-21.
7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.