Sigma Leonis

Sigma Leonis, Latinized from σ Leonis, is a blue-white hued star in the zodiac constellation Leo that is visible to the naked eye with an apparent visual magnitude of 4.0.^[3] Its annual parallax shift of 15.24 mas as seen from Earth implies a distance around 210 light years from the Sun. It is moving closer to the Sun with a radial velocity of –5 km/s.^[7]

Sigma Leonis

Observation data Epoch J2000      Equinox J2000
Constellation	Leo[1]
Right ascension	11h 21m 08.1943s[2]
Declination	+06° 01′ 45.558″[2]
Apparent magnitude (V)	4.046[3]
Characteristics
Evolutionary stage	main sequence[4]
Spectral type	B9.5 Vs[5]
U−B color index	−0.12[6]
B−V color index	−0.06[6]
Astrometry
Radial velocity (Rv)	−5.3[7] km/s
Proper motion (μ)	RA: −91.76[2] mas/yr Dec.: −12.83[2] mas/yr
Parallax (π)	15.24±0.81 mas[2]
Distance	210 ± 10 ly (66 ± 3 pc)
Absolute magnitude (MV)	−0.10[1]
Details
Mass	2.76[8] M☉
Radius	3.07±0.23[9] R☉
Luminosity	133[1] L☉
Surface gravity (log g)	3.83±0.03[10] cgs
Temperature	11,000±1,000[9] K
Metallicity [Fe/H]	+0.0[11] dex
Rotational velocity (v sin i)	70[12] km/s
Age	293[8] Myr
Other designations
σ Leo, 77 Leo, BD−06°2437, FK5 427, HD 98664, HIP 55434, HR 4386, SAO 118804[13]
Database references
SIMBAD	data

Chini et al. (2012) list this as a single-lined spectroscopic binary system.^[5] The visible component has a stellar classification of B9.5 Vs,^[5] indicating it is a B-type main-sequence star. It is a suspected magnetic Ap star that shows an abundance anomaly with the element silicon.^[14] Sigma Leonis has an estimated 2.76 times the mass of the Sun^[8] and 3.07 times the Sun's radius.^[9] It is about 293 million years old^[8] with a projected rotational velocity of 70 km/s.^[12] The star is radiating 133 times the Sun's luminosity from its photosphere^[1] at an effective temperature of 11,000 K.^[9]

Name

In Chinese, 太微右垣 (Tài Wēi Yòu Yuán), meaning Right Wall of Supreme Palace Enclosure, refers to an asterism consisting of σ Leonis, β Virginis, ι Leonis, θ Leonis and δ Leonis.^[15] Consequently, the Chinese name for σ Leonis itself is 太微右垣二 (Tài Wēi Yòu Yuán èr, English: the Second Star of Right Wall of Supreme Palace Enclosure.),^[16] representing 西上將 (Xīshǎngjiāng), meaning The First Western General.^[17] 西上將 (Xīshǎngjiāng), spelled Shang Tseang by R.H. Allen, means "the Higher General".^[18]