21 Comae Berenices
{{short description|Star in the constellation Coma Berenices}}
{{Starbox begin}}
{{Starbox image
| image = 250px
| caption = A visual band light curve for UU Comae Berenices from MOST data. Adapted from Paunzen et al. (2019)
}}
{{Starbox observe
| epoch = J2000.0
| equinox = J2000.0 (ICRS)
| constell = Coma Berenices
| appmag_v = 5.47 or {{nowrap|5.41 – 5.46}}
}}
{{Starbox character
}}
{{Starbox astrometry
| prop_mo_ra = −12.474
| prop_mo_dec = −9.085
| parallax = 12.0785
| p_error = 0.1214
}}
{{Starbox detail
| mass = {{Val|2.29|0.10}}
| radius = {{Val|2.6|0.2}}
| metal_fe =
| gravity = {{Val|3.9|0.2}}
| age_myr = 400–800
| luminosity = {{Val|38.2|1.3}}
| temperature = {{Val|8900|200|fmt=commas}}
| rotational_velocity = {{Val|63|2}}
| rotation = 2.05219 d
}}
{{Starbox catalog
| names = {{odlist | name=Kissīn | V=UU Com | F=21 Com | BD=+25°2517 | HD=108945 | HIP=61071 | HR=4766 | SAO=82346 }}
}}
{{Starbox reference
| Simbad = 21+com
}}
{{Starbox end}}
21 Comae Berenices is a variable star in the northern constellation of Coma Berenices. It has the variable star designation UU Comae Berenices, while 21 Comae Berenices is the Flamsteed designation.{{Cite web |title=21 Comae Berenices - Star in Coma Berenices {{!}} TheSkyLive.com |url=https://theskylive.com/sky/stars/21-comae-berenices-star |access-date=2023-06-13 |website=theskylive.com}}{{Cite web |last=Guide |first=Universe |date=25 January 2015 |title=21 Comae Berenices Star Facts |url=https://www.universeguide.com/star/61071/21comaeberenices |access-date=13 June 2023 |website=Universe Guide |language=en-US}}
About
According to R. H. Allen, English orientalist Thomas Hyde attributed the ancient title Kissīn to this star, a name that comes from a climbing plant – either bindweed or dog rose. This star has a white hue and is just visible to the naked eye with an apparent visual magnitude that fluctuates around 5.47. Based upon parallax measurements, it is located at a distance of approximately 270 light years away from the Sun. It is a single star but is a confirmed physical member of the Melotte 111 open cluster.
History
This object has been studied extensively since 1953, producing some occasionally contradictory results such as hints of pulsational behavior or a binary companion. It is a weakly magnetic chemically peculiar star of type CP2, or Ap star, that is most likely on the main sequence. The stellar classification is A3p SrCr, where the suffix notation indicates abundance anomalies of the iron-peak element chromium, as well as strontium.
In 1950, Olin Jeuck Eggen reported that the brightness of 21 Comae Berenices is variable. This is an Alpha2 Canum Venaticorum (ACV) variable, which indicates it varies in luminosity as it rotates due to spots on its surface created by a magnetic field. The range of variation has an amplitude of 0.02 magnitude and a period of just over two days. Samus et al. (2017) have it classified as a low-amplitude Delta Scuti variable, although this is disputed.
The age of the Melotte 111 cluster, and therefore this star, lies in the range of 400–800 million years. The star has a projected rotational velocity of 63 km/s, with a polar inclination of 64° or greater, resulting in a rotation period of 2.05 days. Stellar evolutionary models yield a mass of around 2.3 times that of the Sun and 2.6 times the Sun's radius for this object. It is radiating 38 times the luminosity of the Sun from its photosphere at an effective temperature of 8,900 K.
References
{{reflist|refs=
{{Cite Gaia EDR3|3959965486205062528}}
{{cite simbad | title=21 Com | access-date=2019-11-01}}
| title=General catalogue of variable stars: Version GCVS 5.1
| last1=Samus' | first1=N. N | last2=Kazarovets | first2=E. V
| last3=Durlevich | first3=O. V | last4=Kireeva | first4=N. N
| last5=Pastukhova | first5=E. N | journal=Astronomy Reports
| volume=61 | issue=1 | pages=80 | year=2017 | postscript=.
| doi=10.1134/S1063772917010085 | bibcode=2017ARep...61...80S | s2cid=125853869 }}
| last1=Eggen | first1=Olin J. | title=Photoelectric Studies.IV. Color-Luminosity Array for Stars in the Region of the Sun
| journal=Astrophysical Journal | date=July 1950 | volume=112 | pages=141-177 | bibcode=1950ApJ...112..141E
| doi=10.1086/145324 | url=https://articles.adsabs.harvard.edu/pdf/1950ApJ...112..141E | access-date=8 February 2025}}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | arxiv=1108.4971
| doi=10.1134/S1063773712050015 | s2cid=119257644 }}
| title=A revisit to the enigmatic variable star 21 Comae
| display-authors=1 | last1=Paunzen | first1=Ernst
| last2=Handler | first2=Gerald | last3=Walczak | first3=Przemysław
| last4=Hümmerich | first4=Stefan | last5=Niemczura | first5=Ewa
| last6=Kallinger | first6=Thomas | last7=Weiss | first7=Werner
| last8=Bernhard | first8=Klaus | last9=Fedurco | first9=Miroslav
| last10=Gütl-Wallner | first10=Anna | last11=Matthews | first11=Jaymie
| last12=Pribulla | first12=Theodor | last13=VaÅko | first13=Martin
| last14=Wallner | first14=Stefan | last15=RóŻański | first15=Tomasz
| journal=Monthly Notices of the Royal Astronomical Society
| volume=485 | issue=3 | pages=4247–4259 | date=May 2019
| doi=10.1093/mnras/stz413 | doi-access=free | arxiv=1904.04809
| bibcode=2019MNRAS.485.4247P | s2cid=104292433 | postscript=. }}
| title=Catalogue of Ap, HgMn and Am stars
| last1=Renson | first1=P. | last2=Manfroid | first2=J.
| journal=Astronomy and Astrophysics | postscript=.
| volume=498 | issue=3 | pages=961–966 | year=2009
| bibcode=2009A&A...498..961R | doi=10.1051/0004-6361/200810788 | doi-access=free }}
| last1=Silaj | first1=J. | last2=Landstreet | first2=J. D.
| title=Accurate age determinations of several nearby open clusters containing magnetic Ap stars
| journal=Astronomy & Astrophysics
| volume=566 | pages=A132 | year=2014
| bibcode=2014A&A...566A.132S | arxiv=1407.4531
| doi=10.1051/0004-6361/201321468 | s2cid=53370832 | postscript=. }}
| first=Richard Hinckley | last=Allen | year=1963
| publisher=Dover Publications Inc. | page=171
| title=Star Names: Their Lore and Meaning
| url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Coma_Berenices*.html
| access-date=2019-11-01 | postscript=. }}
}}
{{Stars of Coma Berenices}}
{{DEFAULTSORT:21 Comae Berenices}}
Category:A-type main-sequence stars
Category:Alpha2 Canum Venaticorum variables