Sigma Coronae Borealis

Not to be confused with S Coronae Borealis.
Sigma Coronae Borealis

A light curve for TZ Coronae Borealis, plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis
σ CrB A (σ2)
Right ascension 16h 14m 40.854s[2]
Declination +33° 51′ 31.02″[2]
Apparent magnitude (V) 5.55[2]
σ CrB B (σ1)
Right ascension 16h 14m 40.394s[2]
Declination +33° 51′ 27.05″[2]
Apparent magnitude (V) 6.419[2]
σ CrB C
Right ascension 16h 13m 56.26666s[3]
Declination +33° 46′ 24.2953″[3]
Apparent magnitude (V) 12.229[4]
Characteristics
σ CrB
Spectral type F6V (A)[5] + G1V (B)[6]
U−B color index +0.045[7]
B−V color index +0.599[7]
Variable type RS CVn[8]
σ CrB C
Spectral type M2.5V[9]
Astrometry
σ CrB A
Radial velocity (Rv)−12.30 ± 0.06[10] km/s
Proper motion (μ) RA: −268.325[11] mas/yr
Dec.: −86.925[11] mas/yr
Parallax (π)44.1346 ± 0.0644 mas[11]
Distance73.9 ± 0.1 ly
(22.66 ± 0.03 pc)
σ CrB B
Radial velocity (Rv)−12.30 ± 0.06[10] km/s
Proper motion (μ) RA: −291.118[12] mas/yr
Dec.: −78.651[12] mas/yr
Parallax (π)44.1475 ± 0.0237 mas[12]
Distance73.88 ± 0.04 ly
(22.65 ± 0.01 pc)
σ CrB C
Radial velocity (Rv)−16.30 ± 10[13] km/s
Proper motion (μ) RA: −265.92[3] mas/yr
Dec.: −83.63[3] mas/yr
Parallax (π)42.8557 ± 0.3965 mas[14]
Distance76.1 ± 0.7 ly
(23.3 ± 0.2 pc)
Orbit[15]
Primaryσ2 CrB primary
Companionσ2 CrB secondary
Period (P)1.139791423(80)
Semi-major axis (a)1.225 ± 0.013 mas
Eccentricity (e)0.0
Inclination (i)28.08 ± 0.34°
Longitude of the node (Ω)207.93 ± 0.67°
Periastron epoch (T)Tnode = 2450127.04855(20)
Argument of periastron (ω)
(secondary)		0.0°
Orbit[15]
Primaryσ2 CrB
Companionσ1 CrB
Period (P)726 ± 62 yr
Semi-major axis (a)5.26 ± 0.35″
Eccentricity (e)0.72 ± 0.01
Inclination (i)32.3 ± 4.1°
Longitude of the node (Ω)28.0 ± 0.5°
Periastron epoch (T)B 1825.2 ± 1.5
Argument of periastron (ω)
(primary)		237.3 ± 6.8°
Orbit[16]
Primaryσ CrB Ca
Companionσ CrB Cb
Period (P)52 yr
Semi-major axis (a)0.111″
Eccentricity (e)0.36
Inclination (i)59°
Longitude of the node (Ω)30°
Periastron epoch (T)B 1963.0
Argument of periastron (ω)
(secondary)		127°
Details
σ1 CrB
Mass1.0[15] M☉
Surface gravity (log g)4.5[15] cgs
Temperature5950 ± 100[15] K
Rotational velocity (v sin i)3 ± 2[15] km/s
Age1 to 3[15] Myr
σ2 CrB primary
Mass1.137 ± 0.037[15] M☉
Radius1.244 ± 0.050[15] R☉
Surface gravity (log g)4.5[15] cgs
Temperature6050 ± 150[15] K
Metallicity [Fe/H]0.0[15] dex
Rotational velocity (v sin i)26 ± 1[15] km/s
Age0.5 to 1.5[15] Gyr
σ2 CrB secondary
Mass1.090 ± 0.036[15] M☉
Radius1.244 ± 0.050[15] R☉
Surface gravity (log g)4.5[15] cgs
Temperature5870 ± 150[15] K
Metallicity [Fe/H]0.0[15] dex
Rotational velocity (v sin i)26 ± 1[15] km/s
Age0.5 to 1.5[15] Gyr
σ CrB C
Mass0.423 ± 0.042[17] M☉
Radius0.437 ± 0.020[17] R☉
Surface gravity (log g)5.0[18] cgs
Temperature3454 ± 63[17] K
Metallicity [Fe/H]−0.06 ± 0.03[17] dex
Age2.95[17] Gyr
Other designations
σ CrB, 17 CrB, BD+34° 2750, HIP 79607 (only AB), SAO 65165, ADS 9979[8]
σ CrB A: σ2 CrB, TZ CrB, GJ 9550B, HD 146361, HR 6064, CCDM J16147+3352A, WDS J16147+3352A, TYC 2583-1846-1[19]
σ CrB B: σ1 CrB, GJ 9550A, HD 146362, HR 6063, CCDM J16147+3352B, WDS J16147+3352B, TYC 2583-1846-2[20]
σ CrB C: GJ 9549, HIP 79551, WDS J16147+3352E, G 180-42[21]
Database references
SIMBADσ CrB
σ1 CrB
σ2 CrB
σ CrB C
ARICNSσ1 CrB
σ2 CrB
σ CrB C

Sigma Coronae Borealis (σ CrB) is a star system in the constellation of Corona Borealis. It is a quintuple star system containing three sunlike main-sequence stars and two other low-mass stars. The combined visual magnitude is 5.3 and the system lies 74 light years from Earth. σ CrB A is the variable star TZ Coronae Borealis.

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  21. ^ "* sig CrB C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.