Sigma Librae

σ Librae
Location of σ Librae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Libra
Right ascension 15h 04m 04.21480s[1]
Declination –25° 16′ 55.0905″[1]
Apparent magnitude (V) 3.20 - 3.46[2]
Characteristics
Spectral type M2.5III[3]
U−B color index +1.94[4]
B−V color index +1.70[4]
Variable type SRb[2]
Astrometry
Radial velocity (Rv)–4.2[5] km/s
Proper motion (μ) RA: −73.484 mas/yr[1]
Dec.: −42.632 mas/yr[1]
Parallax (π)12.539 ± 0.3 mas[1]
Distance260.9+5.2
−6.3 ly
(80.02+1.61
−1.92 pc)[6]
Absolute magnitude (MV)–1.5[7]
Details
Mass2.2[8] M☉
Radius108[9] – 134.8[10] R☉
Luminosity1,800[11][a] L☉
Surface gravity (log g)0.9 ± 0.3[12] cgs
Temperature3,596[8][11] K
Metallicity [Fe/H]0.00[12] dex
Other designations
Brachium, 20 Librae, CD–24 11834, FK5 556, HD 133216, HIP 73714, HR 5603, SAO 183139.,[13] WDS 15041-2517[14]
Database references
SIMBADdata

Sigma Librae (σ Librae, abbreviated Sigma Lib, σ Lib) is a binary star[14] in the constellation of Libra. The apparent visual magnitude is +3.29,[4] making it visible to the naked eye. Based upon parallax measurements, this system is at a distance of roughly 260 light-years (80 parsecs) from the Sun, with a 2% margin of error.[1] At that distance, the visual magnitude is diminished by 0.20 ± 0.17 from extinction caused by intervening gas and dust.[12]

The two components are designated Sigma Librae A (officially named Brachium /ˈbreɪkiəm/,[15] the traditional name for the system)[16] and B.

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  11. ^ a b Cite error: The named reference halabi was invoked but never defined (see the help page).
  12. ^ a b c Cite error: The named reference aaa533_A107 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  14. ^ a b Cite error: The named reference WDS was invoked but never defined (see the help page).
  15. ^ "brachium". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  16. ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.


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