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{{Starbox begin {{Starbox begin|title=Sigma Coronae Borealis}}
{{Starbox observe 3s
| name=Sigma Coronae Borealis
|epoch=]
|constell=]
|component1=σ<sup>2</sup> CrB (σ CrB A)
|ra1={{RA|16|14|40.854}}<ref name=TYC2>{{cite journal|title=The Tycho-2 catalogue of the 2.5 million brightest stars|author=Høg, E.|display-authors=etal|date=2000|journal=Astronomy and Astrophysics|volume=355|pages=L27–L30|bibcode=2000A&A...355L..27H}}</ref>
|dec1={{DEC|+33|51|31.02}}<ref name=TYC2/>
|appmag_v1=5.55<ref name=TYC2/>
|component2=σ<sup>1</sup> CrB (σ CrB B)
|ra2={{RA|16|14|40.394}}<ref name=TYC2/>
|dec2={{DEC|+33|51|27.05}}<ref name=TYC2/>
|appmag_v2=6.419<ref name=TYC2/>
|component3=σ CrB C
|ra3={{RA|16|13|56.26666}}<ref name=HIP>{{cite journal|title=Validation of the new Hipparcos reduction|url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL|author=van Leeuwen, F.|display-authors=etal|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|date=2007|arxiv=0708.1752|bibcode=2007A&A...474..653V|doi=10.1051/0004-6361:20078357}}</ref>
|dec3={{DEC|+33|46|24.2953}}<ref name=HIP/>
|appmag_v3=12.229<ref name=UCAC4>{{cite journal|author=Zacharias, N.|display-authors=etal|title=The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)|journal=VizieR On-line Data Catalog|volume=1322|url=http://adsabs.harvard.edu/abs/bibcode=2012yCat.1322....0Z|date=2012|bibcode=2012yCat.1322....0Z}}</ref>
}} }}
{{Starbox observe {{Starbox character
|component=σ CrB
| epoch=J2000
|class=F6V (A)<ref name=Strassmeier>{{cite journal|title=Chromospheric activity in G and K giants: the spectroscopic data base|author=Strassmeier, K. G.|journal=Astronomy and Astrophysics Supplement|volume=103|number=103|pages=413–425|bibcode=1994A&AS..103..413S|date=1994}}</ref> + G1V (B)<ref name=Gray>{{cite journal|bibcode=2003AJ....126.2048G|doi=10.1086/378365|arxiv=astro-ph/0308182|title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I|journal=The Astronomical Journal|volume=126|issue=4|pages=2048|year=2003|last1=Gray|first1=R. O.|last2=Corbally|first2=C. J.|last3=Garrison|first3=R. F.|last4=McFadden|first4=M. T.|last5=Robinson|first5=P. E.}}</ref>
| ra={{RA|16|14|40.85557}}<ref name="SIMBAD">{{cite web |url =http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Sigma+Coronae+Borealis&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Sigma Coronae Borealis - Variable of RS CVn type|work = SIMBAD Astronomical Database|publisher=Centre de Données astronomiques de Strasbourg|accessdate = 23 November 2014}}</ref>
|b-v=+0.599<ref name=UBV>{{cite journal|title=Photometric and astrometric observations of close visual binaries|author1=Rakos, K. D.|author2=Albrecht, R.|author3=Jenkner, H.|author4=Kreidl, T.|author5=Michalke, R.|author6=Oberlerchner, D.|author7=Santos, E.|author8=Schermann, A.|author9=Schnell, A.|author10=Weiss, W.|journal=Astronomy and Astrophysics Supplement Series|volume=47|issue=221–235|pages=221|date=1982|bibcode=1982A&AS...47..221R}}</ref>
| dec={{DEC|+33|51|30.9497}}<ref name="SIMBAD"/>
| appmag_v=5.64<ref name="SIMBAD"/> |u-b=+0.045<ref name=UBV/>
|variable=]<ref name=SimbadAB/>
| constell=]
}}
{{Starbox character|no_heading=y
|component=σ CrB C
|class=M2.5V<ref name=Reid>{{cite journal|doi=10.1086/117655|bibcode=1995AJ....110.1838R|title=The Palomar/MSU Nearby-Star Spectroscopic Survey. I. The Northern M Dwarfs -Bandstrengths and Kinematics|journal=The Astronomical Journal|volume=110|pages=1838|year=1995|last1=Reid|first1=I. Neill|last2=Hawley|first2=Suzanne L.|last3=Gizis|first3=John E.}}</ref>
}} }}
{{Starbox astrometry {{Starbox astrometry
|component1=σ CrB AB
| radial_v = -12.30
|radial_v=−12.30 ± 0.06<ref name=Karatas>{{cite journal|bibcode=10.1111/j.1365-2966.2004.07588.x|doi=2004MNRAS.349.1069K|arxiv=astro-ph/0404219|doi-broken-date=2017-04-22|title=Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution|journal=Monthly Notices of the Royal Astronomical Society|volume=349|pages=1069|author1=Karataş|first1=Y.|last2=Bilir|first2=S.|last3=Eker|first3=Z.|last4=Demircan|first4=O.|year=2004}}</ref>
| prop_mo_ra = -263.39
|prop_mo_ra=−263.39<ref name=HIP/>
| prop_mo_dec = -92.67
|prop_mo_dec=−92.67<ref name=HIP/>
| parallax = 43.93
|parallax=43.93
| p_error = 0.10
|p_error=0.10
| parallax_footnote =<ref name=Lestrade>{{cite journal|display-authors=4|author=Lestrade, J.-F.|author2=Preston, R. A.|author3=Jones, D. L.|author4=Phillips, R. B.|author5=Rogers, A. E. E.|author6=Titus, M. A.|author7=Rioja, M. J.|author8=Gabuzda, D. C.|date=1999|title=High-precision VLBI astrometry of radio-emitting stars|journal=Astronomy and Astrophysics|volume=344|pages=1014–26|bibcode=1999A&A...344.1014L}}</ref>
|parallax_footnote=<ref name=Lestrade>{{cite journal|bibcode=1999A&A...344.1014L|title=High-precision VLBI astrometry of radio-emitting stars|journal=Astronomy and Astrophysics|volume=344|pages=1014|author1=Lestrade|first1=J.-F.|last2=Preston|first2=R. A.|last3=Jones|first3=D. L.|last4=Phillips|first4=R. B.|last5=Rogers|first5=A. E. E.|last6=Titus|first6=M. A.|last7=Rioja|first7=M. J.|last8=Gabuzda|first8=D. C.|year=1999}}</ref>
| dist_ly = <!--Distance (in light years)-->
|absmag_v=4.64 ± 0.01 (σ<sup>1</sup> CrB)<br>4.35 ± 0.02 (σ<sup>2</sup> CrB A)<br>4.74 ± 0.02 (σ<sup>2</sup> CrB B)
| dist_pc = <!--Distance (in parsecs)-->
|component2=σ CrB C

|radial_v2=−16.30 ± 10<ref name=Hawley>{{cite journal|bibcode=1996AJ....112.2799H|doi=10.1086/118222|title=The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity|journal=The Astronomical Journal|volume=112|pages=2799|year=1996|last1=Hawley|first1=Suzanne L.|last2=Gizis|first2=John E.|last3=Reid|first3=I. Neill}}</ref>
}}
|prop_mo_ra2=−265.92<ref name=HIP/>
|prop_mo_dec2=−83.63<ref name=HIP/>
|parallax2=45.40
|p_error2=3.71
|parallax_footnote2=<ref name=HIP/>
|absmag_v2=
}}
{{Starbox orbit
|reference=<ref name=Raghavan>{{cite journal|bibcode=2009ApJ...690..394R|doi=10.1088/0004-637X/690/1/394|arxiv=0808.4015|title=THE VISUAL ORBIT OF THE 1.1 DAY SPECTROSCOPIC BINARY σ2CORONAE BOREALIS FROM INTERFEROMETRY AT THE CHARA ARRAY|journal=The Astrophysical Journal|volume=690|pages=394|year=2009|last1=Raghavan|first1=Deepak|last2=McAlister|first2=Harold A.|last3=Torres|first3=Guillermo|last4=Latham|first4=David W.|last5=Mason|first5=Brian D.|last6=Boyajian|first6=Tabetha S.|last7=Baines|first7=Ellyn K.|last8=Williams|first8=Stephen J.|last9=Brummelaar|first9=Theo A. ten|last10=Farrington|first10=Chris D.|last11=Ridgway|first11=Stephen T.|last12=Sturmann|first12=Laszlo|last13=Sturmann|first13=Judit|last14=Turner|first14=Nils H.}}</ref>
|primary=σ<sup>2</sup> CrB A
|name=σ<sup>2</sup> CrB B
|period_unitless=1.139791423(80)
|axis_unitless=1.225 ± 0.013 mas
|eccentricity=0.0
|inclination=28.08 ± 0.34
|node=207.93 ± 0.67
|periastron=''T''<sub>node</sub>&nbsp;{{=}}&nbsp;2450127.04855(20)
|periarg=0.0
}}
{{Starbox orbit
|reference=<ref name=Raghavan/>
|primary=σ<sup>2</sup> CrB
|name=σ<sup>1</sup> CrB
|period=726 ± 62
|axis=5.26 ± 0.35
|eccentricity=0.72 ± 0.01
|inclination=32.3 ± 4.1
|node=28.0 ± 0.5
|periastron=] 1825.2 ± 1.5
|periarg=237.3 ± 6.8
}}
{{Starbox orbit
|reference=<ref name=Heintz/>
|primary=σ CrB Ca
|name=σ CrB Cb
|period=52
|axis=0.111
|eccentricity=0.36
|inclination=59
|node=30
|periastron=B 1963.0
|periarg=127
}}
{{Starbox detail
|component1=σ<sup>1</sup> CrB
|mass=1.0<ref name=Raghavan/>
|radius=
|temperature=5950 ± 100<ref name=Raghavan/>
|rotational_velocity=3 ± 2<ref name=Raghavan/>
|metal_fe=
|gravity=4.5<ref name=Raghavan/>
|luminosity=
|age_myr=1 to 3<ref name=Raghavan/>
}}
{{Starbox detail|no_heading=y
|component1=σ<sup>2</sup> CrB A
|mass=1.137 ± 0.037<ref name=Raghavan/>
|radius=1.244 ± 0.050<ref name=Raghavan/>
|temperature=6050 ± 150<ref name=Raghavan/>
|rotational_velocity=26 ± 1<ref name=Raghavan/>
|metal_fe=0.0<ref name=Raghavan/>
|gravity=4.5<ref name=Raghavan/>
|luminosity=
|age=0.5 to 1.5<ref name=Raghavan/>
|component2=σ<sup>2</sup> CrB B
|mass2=
|radius2=
|temperature2=
|rotational_velocity2=26 ± 1<ref name=Raghavan/>
|metal_fe2=0.0<ref name=Raghavan/>
|gravity2=4.5<ref name=Raghavan/>
|luminosity2=
|age2=0.5 to 1.5<ref name=Raghavan/>
}}
{{Starbox detail|no_heading=y
|component1=σ CrB C
|mass= 0.423 ± 0.042<ref name=Mann/><!-- not the theoretical values -->
|radius=0.437 ± 0.020<ref name=Mann/>
|temperature=3454 ± 63<ref name=Mann/>
|metal_fe=−0.06 ± 0.03<ref name=Mann>{{cite journal|bibcode=2015ApJ...804...64M|doi=10.1088/0004-637X/804/1/64|arxiv=1501.01635}}</ref>
|gravity=5.0<ref name=Lepine>{{cite journal|title=A Spectroscopic Catalog of the Brightest (J < 9) M Dwarfs in the Northern Sky|author=Lépine, S.|display-authors=etal|date=2013|journal=The Astronomical Journal|volume=145|issue=4|bibcode=2013AJ....145..102L|doi=10.1088/0004-6256/145/4/102|arxiv=1206.5991}}</ref>
|age_gyr=2.95<ref name=Mann/><!-- 10^(9.47 ± 0.58) -->
}}
{{Starbox catalog {{Starbox catalog
|names={{odlist|ADS=9979&nbsp;AB|CCDM=J16147+3352AB|WDS=J16147+3352AB|B=σ CrB|F=17 CrB|V=TZ CrB|BD=+34° 2750|GJ=9550|HD=146361|HIP=79607|HR=6063|SAO=65165}}<ref name=SimbadAB>{{cite simbad|title=* sig CrB|accessdate=20 April 2017}}</ref>
| names= Sigma Coronae Borealis, TZ Coronae Borealis, ] 146361, ]+34° 2750, ]&nbsp;79607, ] 21863, ] 65165.
|component1=σ<sup>1</sup> CrB
|names1={{odlist|HD=146362|HR=6064|TYC=2583-1846-2}}<ref name=Simbad1>{{cite simbad|title=* sig01 CrB|accessdate=20 April 2017}}</ref>
|component2=σ<sup>2</sup> CrB
|names2={{odlist|TYC=2583-1846-1}}<ref name=Simbad2>{{cite simbad|title=* sig02 CrB|accessdate=20 April 2017}}</ref>
|component3=σ CrB C
|names3={{odlist|GJ=9549|G=180-42|HIP=79551|LP=275-6}}<ref name=SimbadC>{{cite simbad|title=* sig CrB C|accessdate=20 April 2017}}</ref>
}} }}
{{Starbox reference {{Starbox reference
| Simbad=sig+CrB |Simbad=sig+CrB|sn=σ CrB
|Simbad2=sig01+CrB|sn2=σ<sup>1</sup> CrB
|Simbad3=sig02+CrB|sn3=σ<sup>2</sup> CrB
|Simbad4=sig+CrB+C|sn4=σ CrB C
|ARICNS=01274|an=σ<sup>1</sup> CrB
|ARICNS2=01275|an2=σ<sup>2</sup> CrB
|ARICNS3=01276|an3=σ CrB C
}} }}
{{Starbox end}} {{Starbox end}}
'''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''' is a quintuple star system in the constellation ], the main components of which are three sunlike stars.<ref name=kalersigma>{{cite web| first1=James B. | last1=Kaler | title=Sigma Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/sigmacrb.html | accessdate=23 November 2014}}</ref> Appearing as a single star of apparent magnitude 5.3 to the unaided eye, Sigma can be separated into 6.6-magnitude Sigma<sup>1</sup> and 5.64-magnitude Sigma<sup>2</sup> when observed with a telescope.<ref name=kalersigma/> The two take 726 years to orbit each other.<ref name="Raghavan 2009">{{cite journal|display-authors=4|author=Raghavan, Deepak|author2=McAlister, Harold A.|author3=Torres, Guillermo|author4=Latham, David W.|author5=Mason, Brian D.|author6=Boyajian, Tabetha S.|author7=Baines, Ellyn K.|author8=Williams, Stephen J.|author9=ten Brummelaar, Theo A.|author10=Farrington, Chris D.|author11=Ridgway, Stephen T.|author12=Sturmann, Laszlo|author13=Sturmann, Judit|author14=Turner, Nils H.|date=2009|title= The Visual Orbit of the 1.1 Day Spectroscopic Binary σ2 Coronae Borealis from Interferometry at the Chara Array|journal=The Astrophysical Journal|volume=690|issue=1|pages=394–406|doi=10.1088/0004-637X/690/1/394 | bibcode=2009ApJ...690..394R|arxiv = 0808.4015 }}</ref> The orbit of Sigma<sup>1</sup> is eccentric, with an average distance of 128 AU, and a minimum of 31 AU and maximum of 225 AU.<ref name=kalersigma/> Sigma<sup>1</sup> is a yellow main sequence star of spectral type G1V and weighing around 1 ].<ref name="Raghavan 2009"/> Sigma<sup>2</sup> is a spectroscopic binary system composed of two stars very close (6 solar radii) together that orbit each other every 1.14 days.<ref name=kalersigma/> These stars are 1.14 and 1.09 times as massive as the Sun,<ref name="Raghavan 2009"/> with spectral types F9V and G0V respectively.<ref name=kalersigma/> Each has a diameter around 1.2 times that of the Sun.<ref name="Raghavan 2009"/> They rotate each other very rapidly, and are very active as a result, with prominent star spots and are classed as ]s.<ref name=kalersigma/> The system emits radio waves.<ref name=Lestrade/> Much further away, at a distance of 14,000 astronomical units (AU), are a pair of red dwarf stars that take 52 years to rotate each other.<ref name="Raghavan 2009"/> This pair has a combined apparent magnitude of 12.24.<ref name="Raghavan 2009"/> Another pair of faint stars that appear nearby were found to be unrelated.<ref name="Raghavan 2009"/>


==Components==
The system is thought to be anywhere from 100 million to 3 billion years old, from measurement of lithium in its spectrum.<ref name="Raghavan 2009"/> Its parallax was measured in 1999, yielding a distance of 74.2 light-years.<ref name=Lestrade/>
The brightest components of Sigma Coronae Borealis form a visual ] and are designated Sigma<sup>1</sup> Corona Borealis and Sigma<sup>2</sup> Corona Borealis, also known as Sigma Corona Borealis B<ref name=Simbad1/> and Sigma Corona Borealis A,<ref name=Simbad2/> respectively. (Sigma<sup>2</sup> Corona Borealis received the designation ''A'' because it is the brighter component.) 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 ] for Sigma<sup>1</sup> and Sigma<sup>2</sup> Corona Borealis has been calculated, with an ] of about 730 years and a high ] of 0.72.<ref name=Raghavan/>

Sigma<sup>2</sup> Corona Borealis itself is a close binary. Here, the two stars are extremely close and orbit fairly quickly, every 1.14 days.<ref name=Raghavan/> This tiny separation of only 0.0279 ]<ref name=Raghavan/> has allowed the two stars to exert ]s on each other, leading to synchronization of their rotation. They have also been classified as ]s (RS CVn)—young, active stars that show variability in their apparent magnitude due to ]s on their surfaces. For that reason they bear the ] '''TZ Coronae Borealis'''.<ref name=SimbadAB/>

Despite Sigma<sup>2</sup> Corona Borealis's two stars being extremely close and difficult to ], this was done successfully 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/>

==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&Prime; along a ] of 103&deg; and cas of 1996, component D was separated from the primary by 88&Prime; along a ] of 82&deg;. However, both of them have different ]s through space and are not related, just optical alignments. 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: while it is known in the WDS as component E, it is also called Sigma Coronae Borealis C.<ref name=Raghavan/>


==References== ==References==
{{reflist}} {{reflist}}

==See also==
*], a quintuple containing an RS CVn binary

==External links==
*{{cite web|first1=James B.|last1=Kaler|title=Sigma Coronae Borealis|work=Stars|publisher=University of Illinois|url=http://stars.astro.illinois.edu/sow/sigmacrb.html}}


{{Stars of Corona Borealis}} {{Stars of Corona Borealis}}

Revision as of 21:47, 22 April 2017

Sigma Coronae Borealis
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis
σ CrB (σ CrB A)
Right ascension 16 14 40.854
Declination +33° 51′ 31.02″
Apparent magnitude (V) 5.55
σ CrB (σ CrB B)
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 (Rv)−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
Distance74.2 ± 0.2 ly
(22.76 ± 0.05 pc)
Absolute magnitude (MV)4.64 ± 0.01 (σ CrB)
4.35 ± 0.02 (σ CrB A)
4.74 ± 0.02 (σ CrB B)
σ CrB C
Radial velocity (Rv)−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
Distance72 ± 6 ly
(22 ± 2 pc)
Orbit
Primaryσ CrB A
Companionσ CrB B
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
Primaryσ CrB
Companionσ 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
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
σ CrB
Mass1.0 M☉
Surface gravity (log g)4.5 cgs
Temperature5950 ± 100 K
Rotational velocity (v sin i)3 ± 2 km/s
Age1 to 3 Myr
σ CrB A
Mass1.137 ± 0.037 M☉
Radius1.244 ± 0.050 R☉
Surface gravity (log g)4.5 cgs
Temperature6050 ± 150 K
Metallicity 0.0 dex
Rotational velocity (v sin i)26 ± 1 km/s
Age0.5 to 1.5 years
σ CrB B
Surface gravity (log g)4.5 cgs
Metallicity 0.0 dex
Rotational velocity (v sin i)26 ± 1 km/s
Age0.5 to 1.5 years
σ CrB C
Mass0.423 ± 0.042 M☉
Radius0.437 ± 0.020 R☉
Surface gravity (log g)5.0 cgs
Temperature3454 ± 63 K
Metallicity −0.06 ± 0.03 dex
Age2.95 Gyr
Other designations
σ CrB, 17 CrB, TZ CrB, BD+34° 2750, GJ 9550, HD 146361, HIP 79607, HR 6063, SAO 65165, ADS 9979 AB, CCDM J16147+3352AB, WDS J16147+3352AB
σ CrB: HD 146362, HR 6064, TYC 2583-1846-2
σ CrB: TYC 2583-1846-1
σ CrB C: GJ 9549, HIP 79551, G 180-42, LP 275-6
Database references
SIMBADσ CrB
σ CrB
σ CrB
σ CrB C
ARICNSσ 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.

Components

The brightest components of Sigma Coronae Borealis form a visual binary and are designated Sigma Corona Borealis and Sigma Corona Borealis, also known as Sigma Corona Borealis B and Sigma Corona Borealis A, respectively. (Sigma Corona Borealis received the designation A because it is the brighter component.) 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 for Sigma and Sigma Corona Borealis has been calculated, with an orbital 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 extremely close and difficult to resolve, this was done successfully 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.

Sigma Coronae Borealis has one common proper motion 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, also known as HIP 79551. It is a red dwarf with a spectral type of M2.5V. It too is thought to be a binary star itself, 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 cas 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. 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.

References

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  11. 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.
  12. ^ 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 σ2CORONAE 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.
  13. ^ 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.
  14. ^ . arXiv:1501.01635. Bibcode:2015ApJ...804...64M. doi:10.1088/0004-637X/804/1/64. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  15. 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.
  16. ^ "* sig01 CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
  17. ^ "* sig02 CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.
  18. "* sig CrB C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 April 2017.

See also

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