Tau Leonis

Tau Leonis (τ Leo) is a star in the zodiac constellation of Leo. Because it is located near the ecliptic, it is subject to occultations by the Moon.^[8] It has an apparent visual magnitude of 5.00,^[2] which is bright enough to be seen with the naked eye. The distance to this star, as estimated using parallax measurements,^[1] is 560 light years. It is moving closer to the Sun with a radial velocity of −9 km/s.^[4]

τ Leonis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Leo
Right ascension	11h 27m 56.23976s[1]
Declination	+02° 51′ 22.5609″[1]
Apparent magnitude (V)	5.00[2]
Characteristics
Spectral type	G8- IIIa[3]
U−B color index	+0.80[2]
B−V color index	+1.005[2]
Astrometry
Radial velocity (Rv)	−8.90[4] km/s
Proper motion (μ)	RA: +16.89[1] mas/yr Dec.: −9.81[1] mas/yr
Parallax (π)	5.80 ± 0.33 mas[1]
Distance	560 ± 30 ly (172 ± 10 pc)
Absolute magnitude (MV)	−1.12±0.124[5]
Details
Mass	3.90±0.19[6] M☉
Radius	25.14±1.55[6] R☉
Luminosity	329.6±39.6[6] L☉
Surface gravity (log g)	2.25±0.05[6] cgs
Temperature	4,910±33[6] K
Metallicity [Fe/H]	−0.07±0.10[6] dex
Age	190±20[6] Myr
Other designations
τ Leo, 84 Leo, BD+03°2504, FK5 1297, HD 99648, HIP 55945, HR 4418, SAO 118875[7]
Database references
SIMBAD	data

This G-type giant star has a stellar classification of G8- IIIa^[3] and currently resides on the red giant branch. It has about 390% of the Sun's mass. The star is much younger than the Sun, with an age of around 190 million years. As an evolved giant, it has expanded to about 25 times the Sun's radius and radiates 330 times the luminosity of the Sun. The effective temperature of the outer atmosphere is 4,910 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 Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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. 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.
5. Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73, S2CID 119187733.
6. Hekker, S.; Meléndez, J. (2007), "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters", Astronomy and Astrophysics, 475 (3): 1003–1009, arXiv:0709.1145, Bibcode:2007A&A...475.1003H, doi:10.1051/0004-6361:20078233, S2CID 10436552.
7. "* tau Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-29.{{cite web}}: CS1 maint: postscript (link)
8. Richichi, A.; et al. (December 2017), "Further Lunar Occultations from the 2.4 m Thai National Telescope", The Astronomical Journal, 154 (6): 4, Bibcode:2017AJ....154..215R, doi:10.3847/1538-3881/aa9068, S2CID 126342371, 215.