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	'''Sigma Coronae Borealis''' ('''σ CrB''') is a ] in the ] of ]. It is a quintuple ] containing three sunlike ]s and two other low-mass stars.		'''Sigma Coronae Borealis''' ('''σ CrB''') is a ] in the ] of ]. It is a quintuple ] containing three sunlike ]s and two other low-mass stars.

			==System components==
	==Components==
	The brightest components of Sigma Coronae Borealis form a visual ] first resolved in the 19th century,<ref name=wds>{{cite journal\|bibcode=2001AJ....122.3466M\|title=The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog\|journal=The Astronomical Journal\|volume=122\|issue=6\|pages=3466\|author1=Mason\|first1=Brian D.\|last2=Wycoff\|first2=Gary L.\|last3=Hartkopf\|first3=William I.\|last4=Douglass\|first4=Geoffrey G.\|last5=Worley\|first5=Charles E.\|year=2001\|doi=10.1086/323920}}</ref> and are designated σ Corona Borealis A and B. More recently, the designations σ<sup>2</sup> and σ<sup>1</sup> Corona Borealis have come into use. Somewhat confusingly, the brighter component A is referred to as σ<sup>2</sup> because it has the higher ].		The brightest components of Sigma Coronae Borealis form a visual ] first resolved in the 19th century,<ref name=wds>{{cite journal\|bibcode=2001AJ....122.3466M\|title=The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog\|journal=The Astronomical Journal\|volume=122\|issue=6\|pages=3466\|author1=Mason\|first1=Brian D.\|last2=Wycoff\|first2=Gary L.\|last3=Hartkopf\|first3=William I.\|last4=Douglass\|first4=Geoffrey G.\|last5=Worley\|first5=Charles E.\|year=2001\|doi=10.1086/323920}}</ref> and are designated σ Corona Borealis A and B. More recently, the designations σ<sup>2</sup> and σ<sup>1</sup> Corona Borealis have come into use. Somewhat confusingly, the brighter component A is referred to as σ<sup>2</sup> because it has the higher ]. A third component, while being separated 635&Prime (translating to a minimum distance of 14,000 au), has a similar ] to the main system and is physically associated. It is known in the ] (WDS), a compilation of observations of double stars, as component E,<ref name=wds/> but it is usually called Sigma Coronae Borealis C.<ref name=Raghavan/>

	Sigma<sup>1</sup> Corona Borealis is a ] like the ], and has similar parameters: a mass roughly equal to that of the Sun, and an ] of 5950 ].<ref name=Raghavan/> A visual ] has been calculated, with a ] of about 730 years and a high ] of 0.72.<ref name=Raghavan/>		Sigma<sup>1</sup> Corona Borealis is a ] like the ], and has similar parameters: a mass roughly equal to that of the Sun, and an ] of 5950 ].<ref name=Raghavan/> A visual ] has been calculated, with a ] of about 730 years and a high ] of 0.72.<ref name=Raghavan/>
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	Despite Sigma<sup>2</sup> Corona Borealis's two stars being separated only by about the diameter of each star, they were ] using the ] ] at the ]. As of 2006, it is the shortest-period binary ever to be resolved. The primary is 13.7% more massive than the Sun, while the secondary is 9.0% more massive than the Sun, and both are 24.4% wider than the Sun.<ref name=Raghavan/>		Despite Sigma<sup>2</sup> Corona Borealis's two stars being separated only by about the diameter of each star, they were ] using the ] ] at the ]. As of 2006, it is the shortest-period binary ever to be resolved. The primary is 13.7% more massive than the Sun, while the secondary is 9.0% more massive than the Sun, and both are 24.4% wider than the Sun.<ref name=Raghavan/>

	~~Sigma Coronae Borealis has one common ] companion: a star or star system that shares the same motion throughout space and must be physically related. That companion is called Sigma~~ Coronae Borealis C,~~<ref name=Raghavan/>~~ also known as HIP 79551. It is a ] with a ] of M2.5V.<ref name=Reid/> It too is ~~thought to be~~ a binary star ~~itself~~, with a companion in a 52-year orbit.<ref name=Heintz>{{cite journal\|doi=10.1086/115340\|bibcode=1990AJ.....99..420H\|title=Photographic astrometry of binary and proper-motion stars\|journal=The Astronomical Journal\|volume=99\|pages=420\|year=1990\|last1=Heintz\|first1=W. D.}}</ref~~> The companion has a mass of {{solar mass\|0.10}}, and has been detected through ].<ref name=Heintz/~~><ref name=Raghavan/>		σ Coronae Borealis C, also known as HIP 79551, appears as a ] with a ] of M2.5V.<ref name=Reid/> It too is a binary star, with a companion in a 52-year orbit. The companion has a mass of {{solar mass\|0.10}} and has been detected through ].<ref name=Heintz>{{cite journal\|doi=10.1086/115340\|bibcode=1990AJ.....99..420H\|title=Photographic astrometry of binary and proper-motion stars\|journal=The Astronomical Journal\|volume=99\|pages=420\|year=1990\|last1=Heintz\|first1=W. D.}}</ref><ref name=Raghavan/>

	==Optical companions==		==Optical companions==
	The ] (WDS), a compilation of observations of double stars, lists several components to the main system. Two of those are listed in the WDS as components C, and D. As of 1984, component C was separated from the primary by 18″ along a ] of 103° and as of 1996, component D was separated from the primary by 88″ along a ] of 82°. However, both of them have different ]s through space and are not related, just optical alignments. A third component, while being separated 635″ (translating to a minimum distance of 14,000 au), has a similar proper motion to the main system: while it is known in the WDS as component E, it is also called Sigma Coronae Borealis C.<ref name=~~Raghavan~~/>		The ] (WDS), a compilation of observations of double stars, lists several components to the main system. Two of those are listed in the WDS as components C, and D. As of 1984, component C was separated from the primary by 18″ along a ] of 103° and as of 1996, component D was separated from the primary by 88″ along a ] of 82°. However, both of them have different ]s through space and are not related, just optical alignments.<ref name=wds/>

	==References==		==References==

Revision as of 16:12, 23 April 2017

Sigma Coronae Borealis
Observation data Epoch J2000 Equinox J2000
Constellation	Corona Borealis
σ CrB A (σ)
Right ascension	16 14 40.854
Declination	+33° 51′ 31.02″
Apparent magnitude (V)	5.55
σ CrB B (σ)
Right ascension	16 14 40.394
Declination	+33° 51′ 27.05″
Apparent magnitude (V)	6.419
σ CrB C
Right ascension	16 13 56.26666
Declination	+33° 46′ 24.2953″
Apparent magnitude (V)	12.229
Characteristics
σ CrB
Spectral type	F6V (A) + G1V (B)
U−B color index	+0.045
B−V color index	+0.599
Variable type	RS CVn

σ CrB C
Spectral type	M2.5V
Astrometry
σ CrB AB
Radial velocity (R_v)	−12.30 ± 0.06 km/s
Proper motion (μ)	RA: −263.39 mas/yr Dec.: −92.67 mas/yr
Parallax (π)	43.93 ± 0.10 mas
Distance	74.2 ± 0.2 ly (22.76 ± 0.05 pc)
Absolute magnitude (M_V)	4.64 ± 0.01 (σ CrB) 4.35 ± 0.02 (σ CrB primary) 4.74 ± 0.02 (σ CrB secondary)
σ CrB C
Radial velocity (R_v)	−16.30 ± 10 km/s
Proper motion (μ)	RA: −265.92 mas/yr Dec.: −83.63 mas/yr
Parallax (π)	45.40 ± 3.71 mas
Distance	72 ± 6 ly (22 ± 2 pc)
Orbit
Primary	σ CrB primary
Companion	σ 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)	T_node = 2450127.04855(20)
Argument of periastron (ω) (secondary)	0.0°
Orbit
Primary	σ CrB
Companion	σ 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) (secondary)	237.3 ± 6.8°
Orbit
Primary	σ CrB Ca
Companion	σ 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
σ CrB
Mass	1.0 `M`_☉
Surface gravity (log g)	4.5 cgs
Temperature	5950 ± 100 K
Rotational velocity (v sin i)	3 ± 2 km/s
Age	1 to 3 Myr


σ CrB primary
Mass	1.137 ± 0.037 `M`_☉
Radius	1.244 ± 0.050 `R`_☉
Surface gravity (log g)	4.5 cgs
Temperature	6050 ± 150 K
Metallicity	0.0 dex
Rotational velocity (v sin i)	26 ± 1 km/s
Age	0.5 to 1.5 years
σ CrB secondary
Mass	1.090 ± 0.036 `M`_☉
Radius	1.244 ± 0.050 `R`_☉
Surface gravity (log g)	4.5 cgs
Temperature	5870 ± 150 K
Metallicity	0.0 dex
Rotational velocity (v sin i)	26 ± 1 km/s
Age	0.5 to 1.5 years

σ CrB C
Mass	0.423 ± 0.042 `M`_☉
Radius	0.437 ± 0.020 `R`_☉
Surface gravity (log g)	5.0 cgs
Temperature	3454 ± 63 K
Metallicity	−0.06 ± 0.03 dex
Age	2.95 Gyr

Other designations
σ CrB, 17 CrB, BD+34° 2750, HIP 79607 (only AB), SAO 65165, ADS 9979
σ CrB A: σ CrB, TZ CrB, GJ 9550B, HD 146361, HR 6064, CCDM J16147+3352A, WDS J16147+3352A, TYC 2583-1846-1
σ CrB B: σ CrB, GJ 9550A, HD 146362, HR 6063, CCDM J16147+3352B, WDS J16147+3352B, TYC 2583-1846-2
σ CrB C: GJ 9549, HIP 79551, WDS J16147+3352E, G 180-42
Database references
SIMBAD	σ CrB
	σ CrB
	σ CrB
	σ CrB C
ARICNS	σ CrB
	σ 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.

System components

The brightest components of Sigma Coronae Borealis form a visual binary first resolved in the 19th century, and are designated σ Corona Borealis A and B. More recently, the designations σ and σ Corona Borealis have come into use. Somewhat confusingly, the brighter component A is referred to as σ because it has the higher right ascension. A third component, while being separated 635&Prime (translating to a minimum distance of 14,000 au), has a similar proper motion to the main system and is physically associated. It is known in the Washington Double Star Catalog (WDS), a compilation of observations of double stars, as component E, but it is usually called Sigma Coronae Borealis C.

Sigma Corona Borealis is a G-type main-sequence star like the Sun, and has similar parameters: a mass roughly equal to that of the Sun, and an effective temperature of 5950 K. A visual orbit has been calculated, with a period of about 730 years and a high eccentricity of 0.72.

Sigma Corona Borealis itself is a close binary. Here, the two stars are extremely close and orbit fairly quickly, every 1.14 days. This tiny separation of only 0.0279 au has allowed the two stars to exert tidal forces on each other, leading to synchronization of their rotation. They have also been classified as RS Canum Venaticorum variables (RS CVn)—young, active stars that show variability in their apparent magnitude due to starspots on their surfaces. For that reason they bear the variable star designation TZ Coronae Borealis.

Despite Sigma Corona Borealis's two stars being separated only by about the diameter of each star, they were resolved using the CHARA optical interferometer at the Mount Wilson Observatory. As of 2006, it is the shortest-period binary ever to be resolved. The primary is 13.7% more massive than the Sun, while the secondary is 9.0% more massive than the Sun, and both are 24.4% wider than the Sun.

σ Coronae Borealis C, also known as HIP 79551, appears as a red dwarf with a spectral type of M2.5V. It too is a binary star, with a companion in a 52-year orbit. The companion has a mass of 0.10 M_☉ and has been detected through astrometry.

Optical companions

The Washington Double Star Catalog (WDS), a compilation of observations of double stars, lists several components to the main system. Two of those are listed in the WDS as components C, and D. As of 1984, component C was separated from the primary by 18″ along a position angle of 103° and as of 1996, component D was separated from the primary by 88″ along a position angle of 82°. However, both of them have different proper motions through space and are not related, just optical alignments.

References

^ Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
^ van Leeuwen, F.; et al. (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.
Zacharias, N.; et al. (2012). "The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". VizieR On-line Data Catalog. 1322. Bibcode:2012yCat.1322....0Z.
Strassmeier, K. G. (1994). "Chromospheric activity in G and K giants: the spectroscopic data base". Astronomy and Astrophysics Supplement. 103 (103): 413–425. Bibcode:1994A&AS..103..413S.
Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365.
^ Rakos, K. D.; Albrecht, R.; Jenkner, H.; Kreidl, T.; Michalke, R.; Oberlerchner, D.; Santos, E.; Schermann, A.; Schnell, A.; Weiss, W. (1982). "Photometric and astrometric observations of close visual binaries". Astronomy and Astrophysics Supplement Series. 47 (221–235): 221. Bibcode:1982A&AS...47..221R.
^ "* sig CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
^ Reid, I. Neill; Hawley, Suzanne L.; Gizis, John E. (1995). "The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics". The Astronomical Journal. 110: 1838. Bibcode:1995AJ....110.1838R. doi:10.1086/117655.
Karataş, Y.; Bilir, S.; Eker, Z.; Demircan, O. (2004). "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution". Monthly Notices of the Royal Astronomical Society. 349 (3): 1069. arXiv:astro-ph/0404219. Bibcode:2004MNRAS.349.1069K. doi:10.1111/j.1365-2966.2004.07588.x.{{cite journal}}: CS1 maint: unflagged free DOI (link)
Lestrade, J.-F.; Preston, R. A.; Jones, D. L.; Phillips, R. B.; Rogers, A. E. E.; Titus, M. A.; Rioja, M. J.; Gabuzda, D. C. (1999). "High-precision VLBI astrometry of radio-emitting stars". Astronomy and Astrophysics. 344: 1014. Bibcode:1999A&A...344.1014L.
Hawley, Suzanne L.; Gizis, John E.; Reid, I. Neill (1996). "The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity". The Astronomical Journal. 112: 2799. Bibcode:1996AJ....112.2799H. doi:10.1086/118222.
^ Raghavan, Deepak; McAlister, Harold A.; Torres, Guillermo; Latham, David W.; Mason, Brian D.; Boyajian, Tabetha S.; Baines, Ellyn K.; Williams, Stephen J.; Brummelaar, Theo A. ten; Farrington, Chris D.; Ridgway, Stephen T.; Sturmann, Laszlo; Sturmann, Judit; Turner, Nils H. (2009). "The Visual Orbit of the 1.1-day Spectroscopic Binary σ Coronae Borealis from Interferometry at the CHARA Array". The Astrophysical Journal. 690: 394. arXiv:0808.4015. Bibcode:2009ApJ...690..394R. doi:10.1088/0004-637X/690/1/394.
^ Heintz, W. D. (1990). "Photographic astrometry of binary and proper-motion stars". The Astronomical Journal. 99: 420. Bibcode:1990AJ.....99..420H. doi:10.1086/115340.
^ Mann, Andrew W.; Feiden, Gregory A.; Gaidos, Eric; Boyajian, Tabetha; von Braun, Kaspar (2015). "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius". The Astrophysical Journal. 804 (1): 38. arXiv:1501.01635. Bibcode:2015ApJ...804...64M. doi:10.1088/0004-637X/804/1/64. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
Lépine, S.; et al. (2013). "A Spectroscopic Catalog of the Brightest (J < 9) M Dwarfs in the Northern Sky". The Astronomical Journal. 145 (4). arXiv:1206.5991. Bibcode:2013AJ....145..102L. doi:10.1088/0004-6256/145/4/102.
"* sig02 CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
"* sig01 CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
"* sig CrB C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.

External links

Kaler, James B. "Sigma Coronae Borealis". Stars. University of Illinois.

Constellation of Corona Borealis

Stars

Bayer	α (Alphecca) β (Nusakan) γ δ ε ζ ζ η θ ι κ λ μ ν ν ξ ο π ρ σ τ υ
Flamsteed	23 Her
Variable	R S T U V W RR RS TY UW
HD	140913 145457 (Kamuy)
Other	ADS 9731 Gliese 611 GJ 3929 NGC 6002 XO-1 (Moldoveanu)

Exoplanets

Bayer	ε Coronae Borealis b κ Coronae Borealis b ο Coronae Borealis b ρ Coronae Borealis b c d e
Other	GJ 3929 b c XO-1b (Negoiu)

Galaxies

NGC	6085 6086 6104 6120 6122
Other	FSC 15307+3253 IC 1166 IC 4539

Galaxy clusters

Abell	2061 2065 2067 2142 2162 RX J1532.9+3021

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