21 Canum Venaticorum

{{Starbox begin

| name = 21 Canum Venaticorum

}}

{{Starbox observe

| epoch = J2000

| constell = Canes Venatici

| ra = {{RA|13|18|14.50967}}

| dec = {{DEC|+49|40|55.4245}}

| appmag_v = +5.14

}}

{{Starbox character

| type =

| class = {{nowrap|B9 IV (Si)}} or {{nowrap|A0 V Si:}}

| b-v = {{Val|−0.049|0.002}}

| u-b =

| variable = α² CVn

}}

{{Starbox astrometry

| radial_v = {{Val|−2.9|2.8}}

| prop_mo_ra = −35.235

| prop_mo_dec = +16.655

| parallax = 11.7559

| p_error = 0.1344

| parallax_footnote =

| absmag_v = 0.48

}}

{{Starbox detail

| source =

| mass = 2.73

| radius = {{Val|2.8|0.3}}

| luminosity = 72.49

| temperature = {{Val|11036|375|fmt=commas}}

| gravity = 4.05

| metal_fe =

| rotational_velocity = 96

| age_myr = 201

}}

{{Starbox catalog

| names = {{odlist | V=BK Canum Venaticorum | F=21 CVn | BD=+50°1994 | FK5=3063 | HD=115735 | HIP=64906 | HR=5023 | SAO=44556 }}

}}

{{Starbox reference

| Simbad = 21+CVn

}}

21 Canum Venaticorum is a single variable star in the northern constellation of Canes Venatici, located 277 light years away from the Sun. This object has the variable star designation BK Canum Venaticorum; 21 Canum Venaticorum is the Flamsteed designation. It is visible to the naked eye as a faint white-hued star with a baseline apparent visual magnitude of +5.14.

According to Garrison et al. (1994) this is a B-type subgiant star with a stellar classification of {{nowrap|B9 IV (Si)}}, where the suffix notation indicates this is a Silicon star. Cowley et al. (1969) listed it with a class of {{nowrap|A0 V Si:}}, which would match an A-type main-sequence star with the ':' indicating some uncertainty in the classification. It is a marginally chemically-peculiar star with weaker than normal helium absorption lines and displaying helium line variability. The widths of the lines of ionized silicon vary with a period of {{Convert|0.88|±|0.02|days|hours|disp=out|abbr=off}}.

21 Canum Venaticorum is classified as an Alpha² Canum Venaticorum type variable star and its brightness varies by 0.04 magnitudes over a period of {{Convert|0.767|days|hours|disp=out|abbr=off}}. Its variability was discovered in 1984 by Juraj Zverko and it was given its variable star designation in 1987. It is around 201 million years old and is spinning with a relatively high projected rotational velocity of 96 km/s. The star has 2.73 times the mass of the Sun and 2.8 times the Sun's radius. It is radiating 72 times the luminosity of the Sun from its photosphere at an effective temperature of 11,036 K.

References

{{reflist|refs=

{{cite journal

| last1=Zverko | first1=J. | title=Classification of Ap-Stars HR 830 and 21 CVn

| journal=Bulletin of the Astronomical Institute of Czechoslovakia

| date=September 1984 | volume=35 | pages=294–299 | bibcode=1984BAICz..35..294Z

| url=https://articles.adsabs.harvard.edu/pdf/1984BAICz..35..294Z | access-date=28 August 2024}}

{{cite journal

| title=The 68th Name-List of Variable Stars | journal=Information Bulletin on Variable Stars

| url=https://articles.adsabs.harvard.edu/pdf/1987IBVS.3058....1K | access-date=28 August 2024}}

{{cite journal

| 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 | doi=10.1134/S1063773712050015

| arxiv=1108.4971 | s2cid=119257644 }}

{{citation

| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.

| title=A catalogue of multiplicity among bright stellar systems

| journal=Monthly Notices of the Royal Astronomical Society

| volume=389 | issue=2 | pages=869–879 | year=2008

| arxiv=0806.2878 | bibcode=2008MNRAS.389..869E

| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | s2cid=14878976 | postscript=. }}

{{citation

| title=Variation of the Si II features in the chemically peculiar star - HD 115735

| last1=Sriraghavan | first1=S. M. | last2=Jayakumar | first2=K.

| last3=Babu | first3=G. S. D. | last4=Sajutha | first4=S.

| journal=Bulletin of the Astronomical Society of India

| volume=32 | issue=2 | page=113 | date=June 2004

| bibcode=2004BASI...32..113S | postscript=. }}

{{citation

| title=Classification of Ap-Stars HR 830 and 21 CVn

| last1=Zverko | first1=J.

| journal=Bulletin of the Astronomical Institute of Czechoslovakia

| volume=35 | page=294 | date=September 1984

| bibcode=1984BAICz..35..294Z | postscript=. }}

{{citation

| title=Abundance Determination in the Chemically Peculiar Cp-Star 21-CANUM-VENATICORUM by Means of Spectrum Synthesis

| display-authors=1 | last1=Zverko | first1=J.

| last2=Zboril | first2=M. | last3=Ziznovsky | first3=J.

| journal=Astronomy and Astrophysics

| volume=283 | issue=3 | page=932 | date=March 1994

| bibcode=1994A&A...283..932Z | postscript=. }}

{{citation

| last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A.

| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets

| journal=The Astrophysical Journal | postscript=.

| volume=804 | issue=2 | pages=146 | year=2015

| bibcode=2015ApJ...804..146D | arxiv=1501.03154

| doi=10.1088/0004-637X/804/2/146 | s2cid=33401607 }}

{{citation

| last1=Garrison | first1=R. F | last2=Gray | first2=R. O

| title=The late B-type stars: Refined MK classification, confrontation with stromgren photometry, and the effects of rotation

| journal=The Astronomical Journal | postscript=.

| volume=107 | pages=1556 | year=1994

| bibcode=1994AJ....107.1556G | doi=10.1086/116967 }}

{{citation

| last1=North | first1=P.