Lambda1 Tucanae

This article is about Lambda¹ Tucanae. For other stars with this Bayer designation, see Lambda Tucanae.

Lambda¹ Tucanae is the Bayer designation for one member of a pair of stars sharing a common proper motion through space,^[8] which lie within the southern constellation of Tucana. As of 2013, the pair had an angular separation of 20.0 arc seconds along a position angle of 82°.^[2] Together, they are barely visible to the naked eye with a combined apparent visual magnitude of 6.21.^[5] Based upon an annual parallax shift for both stars of approximately 16.5^[1][3] mas as seen from Earth, this system is located roughly 198 light years from the Sun.

Lambda¹ Tucanae

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Tucana
A
Right ascension	00h 52m 24.5198s[1]
Declination	−69° 30′ 13.5440″[1]
Apparent magnitude (V)	6.70[2]
B
Right ascension	00h 52m 28.3487s[3]
Declination	−69° 30′ 10.3819″[3]
Apparent magnitude (V)	7.35[2]
Characteristics
A
Spectral type	F7 IV-V[4]
U−B color index	+0.07[5]
B−V color index	+0.55[5]
B
Spectral type	G0/2V[4]
Astrometry
A
Radial velocity (Rv)	+29.4±0.2[6] km/s
Proper motion (μ)	RA: 3.849±0.050[1] mas/yr Dec.: −67.462±0.040[1] mas/yr
Parallax (π)	16.4907 ± 0.0293 mas[1]
Distance	197.8 ± 0.4 ly (60.6 ± 0.1 pc)
Absolute magnitude (MV)	+2.68[7]
B
Proper motion (μ)	RA: 9.966±0.062[3] mas/yr Dec.: −79.096±0.052[3] mas/yr
Parallax (π)	16.5242 ± 0.0361 mas[3]
Distance	197.4 ± 0.4 ly (60.5 ± 0.1 pc)
Details
A
Mass	1.55[8] M☉
Luminosity	7[9] L☉
Surface gravity (log g)	3.90[10] cgs
Temperature	6,325[10] K
Metallicity [Fe/H]	+0.09[10] dex
Age	2.6[10] Gyr
B
Mass	1.38[8] M☉
Radius	1.86[3] R☉
Luminosity	3.534[3] L☉
Surface gravity (log g)	3.94[11] cgs
Temperature	5,797[3] K
Metallicity [Fe/H]	+0.04[11] dex
Rotational velocity (v sin i)	3.6[12] km/s
Other designations
DUN 2, CCDM J00524-6930AB, WDS J00524-6930AB[13]
A: λ1 Tucanae, CPD−70 37, HD 5190, HIP 4084, HR 252, SAO 248269[13]
B: CPD−70 38, HD 5208, HIP 4088, SAO 248271[13]
Database references
SIMBAD	data
	companion

The brighter member, component A, is a magnitude 6.70^[2] F-type star with a stellar classification of F7 IV-V.^[4] The luminosity class may indicate that, at the age of 2.6 billion years,^[10] it is beginning to evolve away from the main sequence. It has an estimated 1.55^[8] times the mass of the Sun and is radiating 7^[9] times the solar luminosity from its photosphere at an effective temperature of 6,325 K.^[10] The magnitude 7.35^[2] companion, component B, has 1.38^[8] times the mass of the Sun. If the pair are gravitationally bound, then their estimated orbital period is 27,000 years.^[8]

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. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
3. 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.
4. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
5. Cousins, A. W. J.; Lagerweij, H. C. (1971), "UBV Observations of Variable Stars", Monthly Notes of the Astronomical Society of Southern Africa, 30: 12, Bibcode:1971MNSSA..30...12C.
6. 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, S2CID 59451347, A61.
7. 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.
8. Tokovinin, Andrei (2014), "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs", The Astronomical Journal, 147 (4): 14, arXiv:1401.6827, Bibcode:2014AJ....147...87T, doi:10.1088/0004-6256/147/4/87, S2CID 56066740, 87.
9. 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, S2CID 118665352.
10. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
11. Casagrande, L.; Schönrich, R.; Asplund, M.; Cassisi, S.; Ramírez, I.; Meléndez, J.; Bensby, T.; Feltzing, S. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
12. Głȩbocki, R.; Gnaciński, P. (2005). "Systematic errors in the determination of stellar rotational velocities". 13th Cambridge Workshop on Cool Stars. 560: 571. Bibcode:2005ESASP.560..571G.
13. "Lambda1 Tucanae". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-11-26.