Editing Corona Borealis (section)

=== Stars ===
{{see also|List of stars in Corona Borealis}}
The seven stars that make up the constellation's distinctive crown-shaped pattern are all 4th-magnitude stars except for the brightest of them, [[Alpha Coronae Borealis]]. The other six stars are [[Theta Coronae Borealis|Theta]], [[Beta Coronae Borealis|Beta]], [[Gamma Coronae Borealis|Gamma]], [[Delta Coronae Borealis|Delta]], [[Epsilon Coronae Borealis|Epsilon]] and [[Iota Coronae Borealis]]. The German cartographer [[Johann Bayer]] gave twenty stars in Corona Borealis [[Bayer designation]]s from Alpha to Upsilon in his 1603 [[star atlas]] ''[[Uranometria]]''. Zeta Coronae Borealis was noted to be a double star by later astronomers and its components designated [[Zeta1 Coronae Borealis|Zeta<sup>1</sup>]] and [[Zeta2 Coronae Borealis|Zeta<sup>2</sup>]]. [[John Flamsteed]] did likewise with Nu Coronae Borealis; classed by Bayer as a single star, it was noted to be two close stars by Flamsteed. He named them 20 and 21 Coronae Borealis in [[Flamsteed designation|his catalogue]], alongside the designations [[Nu1 Coronae Borealis|Nu<sup>1</sup>]] and [[Nu2 Coronae Borealis|Nu<sup>2</sup>]] respectively.<ref name=wagman>{{cite book  | last = Wagman  | first = Morton  | year = 2003  | title = Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others | publisher = The McDonald & Woodward Publishing Company | location = Blacksburg, Virginia | isbn = 978-0-939923-78-6 |pages=117–18}}</ref> Chinese astronomers deemed nine stars to make up the asterism, adding [[Pi Coronae Borealis|Pi]] and [[Rho Coronae Borealis]].<ref name=ridpathCB>{{cite web| url=http://www.ianridpath.com/startales/coronaborealis.html#chinese | title=Corona Borealis |last1=Ridpath|first1=Ian|publisher=self-published  |work=Star Tales | access-date= 24 November 2014}}</ref> Within the constellation's borders, there are 37 stars brighter than or equal to [[apparent magnitude]]&nbsp;6.5.{{efn|1=Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.<ref>{{cite web|url=http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|title=The Bortle Dark-Sky Scale|last=Bortle|first=John E.|date=February 2001|work=[[Sky & Telescope]]|access-date=29 November 2014|archive-date=31 March 2014|archive-url=https://web.archive.org/web/20140331202746/http://www.skyandtelescope.com/resources/darksky/3304011.html?page=1&c=y|url-status=dead}}</ref>}}<ref name=tirionconst/>

[[File:CoronaBorealisCC.jpg|thumb|left|The constellation Corona Borealis as it can be seen by the naked eye]]
Alpha Coronae Borealis (officially named Alphecca by the IAU, but sometimes also known as Gemma) appears as a blue-white star of magnitude&nbsp;2.2.<ref>{{cite journal
 | author=Johnson, H. L.
 | author2=Iriarte, B.
 | author3=Mitchell, R. I.
 | author4=Wisniewskj, W. Z.
 | title=UBVRIJKL photometry of the bright stars
 | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99
 | date=1966
 | bibcode=1966CoLPL...4...99J }}</ref> In fact, it is an [[Algol]]-type [[Binary star#eclipsing binaries|eclipsing binary]] that varies by 0.1&nbsp;magnitude with a period of 17.4&nbsp;days.{{sfn|Ridpath|Tirion|2001|pp=126–28}} The primary is a [[A-type main-sequence star|white main-sequence star]] of [[Stellar classification#Spectral types|spectral type]] A0V that is 2.91&nbsp;times the [[mass of the Sun]] ({{Solar mass|link=y}}) and 57 times as [[luminosity|luminous]] ({{Solar luminosity|link=y}}), and is surrounded by a [[debris disk]] out to a radius of around 60&nbsp;[[astronomical unit]]s (AU).<ref name="Pawellek 2014">{{cite journal|author1=Pawellek, Nicole |author2=Krivov, Alexander V. |author3=Marshall, Jonathan P. |author4=Montesinos, Benjamin |author5=Ábrahám, Péter |author6=Moór, Attila |author7=Bryden, Geoffrey |author8=Eiroa, Carlos |date=2014|title=Disk Radii and Grain Sizes in Herschel-resolved Debris Disks|journal=The Astrophysical Journal|volume=792|issue=1|id=65|pages=19|bibcode=2014ApJ...792...65P | doi=10.1088/0004-637X/792/1/65|arxiv = 1407.4579 |s2cid=119282523 }}</ref> The secondary companion is a [[G-type main-sequence star|yellow main-sequence star]] of spectral type G5V that is a little smaller (0.9 times) the diameter of the Sun.<ref name="aaa403">{{cite journal |author1=Güdel, M. |author2=Arzner, K. |author3=Audard, M. |author4=Mewe, R. | title=Tomography of a Stellar X-ray Corona: Alpha Coronae Borealis | journal=Astronomy and Astrophysics | volume=403 | pages=155–71 |date=2003 | doi=10.1051/0004-6361:20030257 | bibcode=2003A&A...403..155G| doi-access=free | url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A53864/datastream/PDF/G%C3%BCdel-2003-Tomography_of_a_stellar_X-ray_corona-%28published_version%29.pdf }}</ref> Lying 75±0.5&nbsp;[[light-year]]s from Earth,<ref name="vanLeeuwen2007">{{cite journal | first=F. | last=van Leeuwen | title=Validation of the New Hipparcos Reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–64 | date=2007 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | arxiv=0708.1752| s2cid=18759600 }}</ref> Alphecca is believed to be a member of the [[Ursa Major Moving Group]] of stars that have a common motion through space.<ref>{{cite journal |author1=King, Jeremy R. |author2=Villarreal, Adam R. |author3=Soderblom, David R. |author4=Gulliver, Austin F. |author5=Adelman, Saul J. | title=Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group | journal=The Astronomical Journal | volume=125 | issue=4 | pages=1980–2017 |date=2003  | doi=10.1086/368241 | bibcode=2003AJ....125.1980K| doi-access=free | url=https://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1248&context=physastro_pubs }}</ref>

Located 112±3&nbsp;light-years away,<ref name="vanLeeuwen2007"/> [[Beta Coronae Borealis]] or Nusakan is a [[spectroscopic binary]] system whose two components are separated by 10&nbsp;AU and orbit each other every 10.5 years.<ref name=kalerbeta>{{cite web| first1=James B. | last1=Kaler | title=Nusakan | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/nusakan.html | access-date=12 November 2014}}</ref> The brighter component is a [[rapidly oscillating Ap star]],<ref name="The radius and effective temperatur">{{cite journal|author1=Bruntt, H. |author2=Kervella, P. |author3=Mérand, A. |author4=Brandão, I.M. |author5=Bedding, T.R. |author6=ten Brummelaar, T.A. |author7=Coudé du Foresto, V. |author8=Cunha, M. S. |author9=Farrington, C. |author10=Goldfinger, P.J. |author11=Kiss, L.L. |author12=McAlister, H.A. |author13=Ridgway, S.T. |author14=Sturmann, J. |author15=Sturmann, L. |author16=Turner, N. |author17=Tuthill, P.G. |date=2010|title=The radius and effective temperature of the binary Ap star β CrB from CHARA/FLUOR and VLT/NACO observations|journal=Astronomy and Astrophysics|volume=512|pages=7|id=A55|bibcode=2010A&A...512A..55B|doi=10.1051/0004-6361/200913405|arxiv = 0912.3215 |s2cid=14468327 }}</ref> pulsating with a period of 16.2&nbsp;minutes. Of spectral type A5V with a [[effective temperature|surface temperature]] of around 7980&nbsp;K, it has around {{Solar mass|2.1|link=y}}, 2.6&nbsp;[[solar radius|solar radii]] ({{Solar radius|link=y}}), and {{Solar luminosity|25.3|link=y}}. The smaller star is of spectral type F2V with a surface temperature of around 6750&nbsp;K, and has around {{Solar mass|1.4}}, {{Solar radius|1.56}}, and between 4 and {{Solar luminosity|5}}.<ref name="The radius and effective temperatur"/> Near Nusakan is [[Theta Coronae Borealis]], a binary system that shines with a combined magnitude of 4.13 located 380±20 light-years distant.<ref name="vanLeeuwen2007"/> The brighter component, Theta Coronae Borealis A, is a blue-white star that spins extremely rapidly—at a rate of around 393&nbsp;km per second. A [[Be star]], it is surrounded by a debris disk.<ref name=kalerthet>{{cite web| first1=James B. | last1=Kaler | title=Theta Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/thetacrb.html | access-date=12 November 2014}}</ref>

Flanking Alpha to the east is Gamma Coronae Borealis, yet another binary star system, whose components orbit each other every 92.94&nbsp;years and are roughly as far apart from each other as the Sun and Neptune.<ref name=kalergamma>{{cite web| first1=James B. | last1=Kaler | title=Gamma Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/gammacrb.html | access-date=18 November 2014 | date = 25 July 2008}}</ref> The brighter component has been classed as a [[Delta Scuti variable]] star,<ref name=SIMBADgamma>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=+Gamma+Coronae+Borealis&submit=SIMBAD+search |title = Gamma Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 21 November 2014}}</ref> though this view is not universal.<ref name=kalergamma/> The components are main sequence stars of spectral types B9V and A3V.<ref>{{cite journal|author1=Malkov, O. Yu. |author2=Tamazian, V.S. |author3=Docobo, J. A. |author4=Chulkov, D. A. |date=2012|title=Dynamical Masses of a Selected Sample of Orbital Binaries |journal=Astronomy & Astrophysics |volume=546|id=A69 |pages=5|doi=10.1051/0004-6361/201219774 | bibcode =2012A&A...546A..69M|doi-access=free }}</ref> Located 170±2&nbsp;light-years away,<ref name="vanLeeuwen2007"/> 4.06-magnitude [[Delta Coronae Borealis]] is a yellow giant star of spectral type G3.5III that is around {{Solar mass|2.4}} and has swollen to {{Solar radius|7.4}}. It has a surface temperature of 5180&nbsp;K.<ref name="Gondoin">{{cite journal|last=Gondoin|first=P.|date=2005|title=The X-ray activity of the slowly rotating G giant δ CrB|journal=Astronomy & Astrophysics|volume=431|issue=3|pages=1027–35|  doi= 10.1051/0004-6361:20041991 | bibcode = 2005A&A...431.1027G
|doi-access=free}}</ref>  For most of its existence, Delta Coronae Borealis was a [[B-type main-sequence star|blue-white main-sequence star]] of spectral type B before it ran out of hydrogen fuel in its core. Its luminosity and spectrum suggest it has just crossed the [[Hertzsprung gap]], having finished burning core hydrogen and just begun burning hydrogen in a shell that surrounds the core.<ref name=kalerdelta>{{cite web| first1=James B. | last1=Kaler | title=Delta Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/deltacrb.html | access-date=21 November 2014}}</ref>

[[Zeta Coronae Borealis]] is a double star with two blue-white components 6.3&nbsp;[[Minute of arc|arcseconds]] apart that can be readily separated at 100x&nbsp;[[magnification#Telescope|magnification]]. The primary is of magnitude&nbsp;5.1 and the secondary is of magnitude&nbsp;6.0.<ref>{{cite book|author1=Kepple, George Robert |author2=Sanner, Glen W. |title=The Night Sky Observers Guide: Spring & summer|publisher=Willmann-Bell|location=Richmond, Virginia|date=1998|pages=111|isbn=978-0-943396-60-6}}</ref> [[Nu Coronae Borealis]] is an [[Double star|optical double]], whose components are a similar distance from Earth but have different [[radial velocity|radial velocities]], hence are assumed to be unrelated.<ref name=kalernu>{{cite web| first1=James B. | last1=Kaler | title=Nu Coronae Borealis | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/nucrb.html | access-date=13 November 2014|date=31 August 2007}}</ref> The primary, [[Nu1 Coronae Borealis|Nu<sup>1</sup> Coronae Borealis]], is a [[red giant]] of spectral type M2III and magnitude 5.2, lying 640±30 light-years distant,<ref name="vanLeeuwen2007"/><ref name=SIMBADnu1>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+147749&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Nu1 Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 13 November 2014}}</ref> and the secondary, [[Nu2 Coronae Borealis|Nu<sup>2</sup> Coronae Borealis]], is an orange-hued giant star of spectral type K5III and magnitude 5.4, estimated to be 590±30&nbsp;light-years away.<ref name="vanLeeuwen2007"/><ref name=SIMBADnu2>{{cite web |url = http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+147767&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id |title = Nu2 Coronae Borealis |work = SIMBAD Astronomical Database |publisher = Centre de Données astronomiques de Strasbourg |access-date = 13 November 2014}}</ref> [[Sigma Coronae Borealis]], on the other hand, is a true multiple star system divisible by small amateur telescopes.{{sfn|Ridpath|Tirion|2001|pp=126–28}} It is actually a complex system composed of two stars around as massive as the Sun that orbit each other every 1.14&nbsp;days, orbited by a third Sun-like star every 726&nbsp;years. The fourth and fifth components are a binary [[red dwarf]] system that is 14,000&nbsp;AU distant from the other three stars.<ref name="Raghavan 2009">{{cite journal|author1=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 |s2cid=14638405 }}</ref> [[ADS 9731]] is an even rarer multiple system in the constellation, composed of six stars, two of which are spectroscopic binaries.<ref name=Tokovinin>{{cite journal|bibcode=1998AstL...24..795T|title=ADS 9731: A new sextuple system|last1=Tokovinin |first1=A.A.|last2=Shatskii|first2=N.I.|last3=Magnitskii|first3=A.K.|volume=24|issue=6|year=1998|pages=795–801|journal=[[Astronomy Letters]]}}</ref>{{efn|1=The components are organised thus: Aa and Ab are yellow-white main sequence stars of spectral types F4V and F5V and 1.35 and 1.32&nbsp;solar masses respectively, which orbit each other every 3.27 days. This pair is in a 450-year orbit with star B, a star of spectral type G4V that has around the same mass as the Sun. Star C is a yellow white star of spectral type F3V around 1.41&nbsp;times as massive as the Sun, which has just started brightening and moving off the main sequence. It is in a 1000-year orbit with a pair of stars, Da and Db, a yellow-white main sequence star of spectral type F7V and a red dwarf of spectral type M3V. Da and Db take 14.28&nbsp;days to orbit each other. Finally the system of stars C and Dab, and the system of stars Aab and B, take more than 20,000&nbsp;years to orbit each other.<ref name=Tokovinin/>}}

Corona Borealis is home to two remarkable [[Variable star|variable]] stars.<ref name="Levy 1998">{{cite book|last=Levy|first=David H.|title=Observing Variable Stars: A Guide for the Beginner|publisher=Cambridge University Press|location=Cambridge, United Kingdom|date=1998|pages=142–43|isbn=978-0-521-62755-9|url=https://books.google.com/books?id=5-O2cd937FMC&pg=PA142}}</ref> [[T Coronae Borealis]] is a [[cataclysmic variable star]] also known as the Blaze Star.{{sfn|Ridpath|Tirion|2001|pp=126–128}} Normally placid around magnitude 10—it has a minimum of 10.2 and maximum of 9.9—it brightens to magnitude 2 in a period of hours, caused by a [[nuclear chain reaction]] and the subsequent explosion. T Coronae Borealis is one of a handful of stars called [[recurrent nova]]e, which include [[T Pyxidis]] and [[U Scorpii]]. An outburst of T Coronae Borealis was first recorded in 1866; its second recorded outburst was in February 1946.<ref name=Schaefer2009>{{Cite journal|last=Schaefer |first=Bradley E.
  |title=Comprehensive Photometric Histories of All Known Galactic Recurrent Novae
  |journal=The Astrophysical Journal Supplement Series
  |volume=187
  |issue=2
  |pages=275–373
  |year=2010
  |arxiv=0912.4426 |doi=10.1088/0067-0049/187/2/275
  |bibcode = 2010ApJS..187..275S |s2cid=119294221
 }}</ref><ref name=Sanford1949>{{cite journal
  |last=Sanford |first=Roscoe F.
  |title=High-Dispersion Spectrograms of T Coronae Borealis.
  |journal=Astrophysical Journal
  |volume=109 |pages=81 |year=1949
  |doi=10.1086/145106
  |bibcode=1949ApJ...109...81S|doi-access=
  }}</ref> T Coronae Borealis started dimming in March 2023 and it is known that before it goes nova it dims for about a year; for this reason it was initially expected to go nova at any time between March and September, 2024.<ref>{{Cite news 
 | first = Mia
 | last = Taylor
 | author-link =
 | author = 
 | author2 =
 | title = Move over, solar eclipse: Scientists predict a once-in-a-lifetime nova explosion in the coming months
 | url = https://www.bbc.com/future/article/20240322-visible-nova-explosion-is-coming#_msocom_1
 | format = 
 | work = 
 | publisher = BBC
 | pages = 
 | page = 
 | date = March 22, 2024
 | access-date = March 23, 2024
 | language = English
 | quote = There's another sign that T CrB is getting ready to blow also, Cooke says. 'We know that before it goes nova it dims for about a year, and T Coronae Borealis started dimming back in March 2023, so that's why we think it's going to go nova between now and the end of September.' As of March 2025, the star has not yet gone nova. 
}}</ref> T Coronae Borealis is a [[binary star]] with a red-hued giant primary and a [[white dwarf]] secondary, the two stars orbiting each other over a period of approximately 8 months.<ref>{{cite book | last = Levy | first = David H. | year = 2005 | title = Deep Sky Objects | pages = [https://archive.org/details/deepskyobjects00davi/page/70 70–71] | publisher = Prometheus Books | location = Amherst, New York | isbn = 978-1-59102-361-6 | url = https://archive.org/details/deepskyobjects00davi/page/70 }}</ref> [[R Coronae Borealis]] is a yellow-hued variable [[supergiant]] star, over 7000 light-years from Earth, and prototype of a class of stars known as [[R Coronae Borealis variable]]s. Normally of magnitude 6, its brightness periodically drops as low as magnitude 15 and then slowly increases over the next several months.<ref>{{cite web| author=Davis, Kate|date= January 2000 |url=http://www.aavso.org/vsots_rcrb |title= R Coronae Borealis | work=Variable star of the season | publisher= American Association of Variable Star Observers (AAVSO) |access-date=14 March 2015}}</ref> These declines in magnitude come about as dust that has been ejected from the star obscures it. Direct imaging with the [[Hubble Space Telescope]] shows extensive dust clouds out to a radius of around 2000&nbsp;AU from the star, corresponding with a stream of fine dust (composed of grains 5&nbsp;[[nanometre|nm]] in diameter) associated with the star's stellar wind and coarser dust (composed of grains with a diameter of around 0.14&nbsp;[[micrometre|μm]]) ejected periodically.<ref>{{cite journal|author1=Jeffers, S. V. |author2=Min, M. |author3=Waters, L. B. F. M. |author4=Canovas, H. |author5=Rodenhuis, M. |author6=de Juan Ovelar, M. |author7=Chies-Santos, A. L. |author8=Keller, C. U. |date=2012|title=Direct imaging of a massive dust cloud around R Coronae Borealis|journal=Astronomy & Astrophysics|volume=539|issue=A56|pages=A56|bibcode=2012A&A...539A..56J |doi=10.1051/0004-6361/201117138|arxiv = 1203.1265 |s2cid=55589182 }}</ref>

There are several other variables of reasonable brightness for amateur astronomer to observe, including three [[Mira variable|Mira-type]] long period variables:<ref name="Levy 1998"/> [[S Coronae Borealis]] ranges between magnitudes 5.8 and 14.1 over a period of 360&nbsp;days.<ref name="AAVSOS">{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10601 |title=S Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index|publisher=American Association of Variable Star Observers |access-date=25 September 2014}}</ref> Located around 1946&nbsp;light-years distant, it shines with a luminosity 16,643&nbsp;times that of the Sun and has a surface temperature of 3033 K.<ref name=Mcdonald>{{cite journal|author=McDonald, I.|author2=Zijlstra, A. A.|author3=Boyer, M.L.|date=2012|title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars|journal=Monthly Notices of the Royal Astronomical Society|volume=427|issue=1|pages=343–57|bibcode=2012MNRAS.427..343M|doi=10.1111/j.1365-2966.2012.21873.x|doi-access=free |arxiv = 1208.2037 |s2cid=118665352}}</ref> One of the reddest stars in the sky,<ref name="Levy 1998"/> [[V Coronae Borealis]] is a cool star with a surface temperature of 2877&nbsp;K that shines with a luminosity 102,831 times that of the Sun and is a remote 8810&nbsp;light-years distant from Earth.<ref name=Mcdonald/> Varying between magnitudes 6.9 and 12.6 over a period of 357&nbsp;days,<ref name="AAVSOV">{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10604 |title=V Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=13 November 2014}}</ref> it is located near the junction of the border of Corona Borealis with Hercules and Bootes.<ref name="Levy 1998"/> Located 1.5° northeast of [[Tau Coronae Borealis]], [[W Coronae Borealis]] ranges between magnitudes 7.8 and 14.3 over a period of 238&nbsp;days.<ref name="AAVSOW">{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10605 |title=W Coronae Borealis|author=Watson, Christopher|date=4 January 2010|work=The International Variable Star Index|publisher=American Association of Variable Star Observers|access-date=9 March 2015}}</ref> Another red giant, [[RR Coronae Borealis]] is a [[stellar classification|M3-type]] [[semiregular variable star]] that varies between magnitudes 7.3 and 8.2 over 60.8 days.<ref name=AAVSORR>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10609 |title=RR Coronae Borealis|author =Otero, Sebastian Alberto |date=15 August 2011 |work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=25 September 2014}}</ref> [[RS Coronae Borealis]] is yet another semiregular variable red giant, which ranges between magnitudes 8.7 to 11.6  over 332 days.<ref name=AAVSORS>{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10610 |title=RS Coronae Borealis|author =Watson, Christopher |date=4 January 2010 |work=The International Variable Star Index|publisher=American Association of Variable Star Observers|access-date=25 July 2015}}</ref>  It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).<ref name=" Jiménez-Esteban">{{cite journal|author1=Jiménez-Esteban, F. M. |author2=Caballero, J. A. |author3=Dorda, R. |author4=Miles-Páez, P. A. |author5=Solano, E. |date=2012|title=Identification of red high proper-motion objects in Tycho-2 and 2MASS catalogues using Virtual Observatory tools|journal=Astronomy & Astrophysics|volume=539|pages=12|doi=10.1051/0004-6361/201118375 |bibcode=2012A&A...539A..86J|arxiv = 1201.5315 |s2cid=53404166 }}</ref> Meanwhile, [[U Coronae Borealis]] is an Algol-type eclipsing binary star system whose magnitude varies between 7.66 and 8.79 over a period of 3.45 days<ref name="AAVSOU">{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=10603 |title=U Coronae Borealis|author=Watson, Christopher |date=4 January 2010|work=The International Variable Star Index |publisher=American Association of Variable Star Observers|access-date=10 March 2015}}</ref>

[[TY Coronae Borealis]] is a [[pulsating white dwarf]] (of ZZ Ceti) type, which is around 70% as massive as the Sun, yet has only 1.1% of its diameter.<ref>{{cite journal|author1=Romero, A. D. |author2=Córsico, A. H. |author3=Althaus, L. G. |author4-link=Kepler de Souza Oliveira |author4=Kepler, S. O. |author5=Castanheira, B. G. |author6=Miller Bertolami, M. M. |date=2012|title=Toward ensemble asteroseismology of ZZ Ceti stars with fully evolutionary models|journal=Monthly Notices of the Royal Astronomical Society|volume=420|issue=2|pages=1462–80| doi=10.1111/j.1365-2966.2011.20134.x |doi-access=free |bibcode=2012MNRAS.420.1462R|arxiv = 1109.6682 |s2cid=55018129 }}</ref> Discovered in 1990, [[UW Coronae Borealis]] is a [[X-ray binary#Low-mass X-ray binary|low-mass X-ray binary]] system composed of a star less massive than the Sun and a neutron star surrounded by an [[accretion disk]] that draws material from the companion star. It varies in brightness in an unusually complex manner: the two stars orbit each other every 111 minutes, yet there is another cycle of 112.6 minutes, which corresponds to the orbit of the disk around the degenerate star. The beat period of 5.5 days indicates the time the accretion disk—which is asymmetrical—takes to [[Precession (mechanical)|precess]] around the star.<ref name="Mason 2012">{{cite journal|author1=Mason, Paul A. |author2=Robinson, Edward L. |author3=Bayless, Amanda J. |author4=Hakala, Pasi J. |date=2012|title=Long-term Optical Observations of Two LMXBS: UW CrB (=MS 1603+260) and V1408 Aql (=4U 1957+115)|journal=The Astronomical Journal|volume=144|issue=4|pages=108 |doi=10.1088/0004-6256/144/4/108 |bibcode=2012AJ....144..108M|hdl=2152/34339 |s2cid=122184568 |hdl-access=free }}</ref>