21 Persei

{{Short description|Star in the constellation Perseus}}

{{Starbox begin

| name = 21 Persei

}}

{{Starbox image

|image=

{{Location mark

|image=Perseus constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=21 Persei

|x=728|y=906

}}

|caption=Location of 21 Persei (circled)

}}

{{Starbox observe

| epoch = J2000

| constell = Perseus

| ra = {{RA|02|57|17.28228}}{{cite DR2|135525184764395776}}

| dec = {{DEC|31|56|03.1976}}

| appmag_v = 5.10{{cite journal | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | s2cid=119257644 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=V/137D/XHIP&HIP=13775 Vizier catalog entry]

}}

{{Starbox character

| class = A2VspSiEu{{cite journal | title=The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars | journal=Astrophysical Journal Supplement | volume=99 | pages=135 | last1=Abt | first1=Helmut A. | last2=Morrell | first2=Nidia I. | year=1995 | bibcode=1995ApJS...99..135A | doi=10.1086/192182 | doi-access=free }}

| b-v = −0.01{{cite journal | bibcode=2006yCat.2168....0M | title=VizieR Online Data Catalog: Homogeneous Means in the UBV System (Mermilliod 1991) | journal=VizieR On-line Data Catalog: II/168. Originally Published in: Institut d'Astronomie | volume=2168 | last1=Mermilliod | first1=J. C. | year=2006 }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=II/168/ubvmeans&LID=%2B100018296 Vizier catalog entry]

| u-b = −0.24

| variable = α² CVn{{cite journal | bibcode=2009yCat....102025S |title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}

}}

{{Starbox astrometry

| radial_v = +8.50{{Cite journal | doi=10.1134/S1063773706110065 | bibcode=2006AstL...32..759G| title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system| journal=Astronomy Letters| volume=32| issue=11| pages=759–771| year=2006| last1=Gontcharov| first1=G. A.|arxiv = 1606.08053 | s2cid=119231169}}

| prop_mo_ra = +1.319

| prop_mo_dec = -30.384

| parallax = 9.8477

| p_error = 0.2575

| parallax_footnote =

| absmag_v = 0.14

}}

{{Starbox detail

| mass = 3.57{{cite journal | bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146 | arxiv=1501.03154 | 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 | volume=804 | issue=2 | pages=146 | year=2015 | last1=David | first1=Trevor J. | last2=Hillenbrand | first2=Lynne A. | s2cid=33401607 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=J/ApJ/804/146/table5&HIP=13775 Vizier catalog entry]

| temperature = 12,585

| luminosity = 88.65

| rotational_velocity = 20

| gravity = 4.05

| metal_fe = +0.90{{cite journal | bibcode=2011A&A...525A..71W | doi=10.1051/0004-6361/201015014 | arxiv=1009.1491 | title=Coudé-feed stellar spectral library – atmospheric parameters | journal=Astronomy & Astrophysics | volume=525 | pages=A71 | year=2010 | last1=Wu | first1=Yue | last2=Singh | first2=H. P. | last3=Prugniel | first3=P. | last4=Gupta | first4=R. | last5=Koleva | first5=M. | s2cid=53480665 }}

}}

{{Starbox catalog

| names = {{odlist | V=LT Per | F=21 Per | BD=+31°509 | FK5=2205 | HD=18296 | HIP=13775 | HR=873 | SAO=56031 | GC=3544 }}{{cite simbad | title=21 Per | access-date=2019-03-29 }}

}}

{{Starbox reference

| Simbad = 21+Persei

}}

{{Starbox end}}

21 Persei is a single,{{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 |date=September 2008

| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E

| postscript=. | arxiv=0806.2878 | s2cid=14878976 }} variable star in the northern constellation of Perseus, located about 331 light years away from the Sun. It is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 5.10 km/s. The object is moving further from the Earth with a heliocentric radial velocity of +8.5 km/s. It has the variable star designation LT Persei; 21 Persei is the Flamsteed designation.

File:LTPerLightCurve.png for LT Persei, plotted from Hipparcos data{{cite web |title=Hipparcos Tools Interactive Data Access |url=https://www.cosmos.esa.int/web/hipparcos/interactive-data-access |website=Hipparcos |publisher=ESA |access-date=8 December 2021}}]]

This is an Ap star with a stellar classification of A2VspSiEu, where the A2V indicates it is an A-type main-sequence star, 's' means narrow "sharp" absorption, and SiEu shows abundance anomalies of the elements silicon and europium. The star is an Alpha² Canum Venaticorum variable, meaning that the star has a strong magnetic field chromium, silicon, and strontium spectral lines. 21 Persei's period of variability is approximately 2.88 days.{{cite journal | title=Third supplement to the catalogue of observed periods of Ap stars | last1=Catalano | first1=F. A. | last2=Renson | first2=P. | last3=Leone | first3=F. | journal=Astronomy and Astrophysics Supplement Series | volume=98 | issue=2 | pages=269–273 | bibcode=1993A&AS...98..269C | year=1993 }}

{{clear left}}