epsilon Ursae Minoris

{{Short description|Binary star system in the constellation Ursa Minor}}

{{Starbox begin

| name = Epsilon Ursae Minoris

}}

{{Starbox image

| image=

{{Location mark

|image=Ursa Minor IAU.svg|alt=|float=center|width=240

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=ε Ursae Minoris

|x=414|y=410

}}

|caption=Location of ε Ursae Minoris (circled)

}}

{{Starbox observe

| epoch = J2000.0

| equinox = J2000.0 (ICRS)

| constell = Ursa Minor

| ra = {{RA|16|45|58.24168}}

| dec = {{DEC|+82|02|14.1233}}

| appmag_v = +4.19

}}

{{Starbox character

| class = {{Nowrap|G5 III + A8-F0 V}}

| b-v = +0.89

| u-b = +0.55

| r-i =

| variable = Eclipsing and RS CVn

}}

{{Starbox astrometry

| radial_v = {{Val|−10.57|0.40}}

| prop_mo_ra = +19.47

| prop_mo_dec = +2.61

| parallax = 10.73

| p_error = 0.39

| parallax_footnote =

| absmag_v = −0.922

}}

{{Starbox orbit

| reference =

| primary =

| name =

| period =

| period_unitless = {{Val|39.48042|0.00012}}

| axis =

| axis_unitless =

| eccentricity = 0.04

| inclination =

| node =

| periastron = 2433083.47 JD

| periarg = 323.5

| periarg_primary =

| k1 = 31.8

| k2 =

}}

{{Starbox detail

| source =

| component1 = ε UMi A

| mass =

| radius =

| luminosity =

| temperature = {{Val|5215|47|fmt=commas}}

| gravity = {{Val|3.21|0.08}}

| metal_fe = {{Val|−0.25|0.04}}

| rotational_velocity = 25.6

| age_gyr =

}}

{{Starbox catalog

| names = {{odlist | B=ε UMi | F=22 Ursae Minoris | BD=+82°498 | FK5=912 | HD=153751 | HIP=82080 | HR=6322 | SAO=2770 | ADS=10242 | GC=22749 | CCDM=16460+8203 }}

}}

{{Starbox reference

| Simbad = eps+UMi

}}

Epsilon Ursae Minoris (ε Ursae Minoris) is a binary star system in the northern circumpolar constellation of Ursa Minor. It is visible to the naked eye with a combined apparent visual magnitude of 4.19. Based upon an annual parallax shift of 10.73 mas as seen from the Earth, it is located around 300 light years from the Sun. The pair are drawing nearer to the Sun with a radial velocity of −10.57 km/s.

File:EpsilonUMiLightCurve.png for Epsilon Ursae Minoris, plotted from TESS data]]

This system forms a detached, single-lined spectroscopic binary with an orbital period of 39.5 days and a low eccentricity of 0.04. Its binary nature was discovered in 1899 by American astronomer W. W. Campbell and the first orbital determination was made in 1910 by Canadian astronomer J. S. Plaskett. The orbital plane is nearly aligned with the line of sight to the Earth, so the pair forms an eclipsing binary. The primary eclipse has a minimum of 4.23 in magnitude, while the secondary minimum is magnitude 4.21. This eclipsing behavior was discovered by German astronomer P. Guthnick using observations between 1946 and 1947.

The primary is an evolved G-type giant star with a stellar classification of G5 III. The secondary is a main sequence star with a class in the range A8-F0 V. One of the pair is an active RS Canum Venaticorum type variable star, which is causing the net brightness to vary with a period that matches the orbital period of the binary. The primary has a high projected rotational velocity of 25.6 km/s, which is likely the result of synchronization effects from tidal interaction with the secondary.

Epsilon Ursae Minoris has a visual companion: a magnitude 12.32 star at an angular separation of 77.0 arc seconds along a position angle of 2°, as of 2014.

According to R. H. Allen's Star Names, the stars α, β, γ, δ & ε Ursae Minoris were collectively known as Circitores. This led to the name Circitores specifically for ε Ursae Minoris appearing in a 1971 NASA memorandum listing star names.

References

{{reflist|refs=

{{cite web

| title=MAST: Barbara A. Mikulski Archive for Space Telescopes

| url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html

| publisher=Space Telescope Science Institute | access-date=20 December 2022}}

{{citation

| title=Validation of the new Hipparcos reduction

| last1=van Leeuwen | first1=F.

| 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 | s2cid=18759600 | postscript=. }}

{{citation

| title=The Rotation of Red Giants and Horizontal Branch Stars (Invited Review)

| last=de Medeiros | first=J. R.

| work=Stellar Rotation, Proceedings of IAU Symposium No. 215, held 11-15 November, 2002 in Cancun, Yucatan, Mexico

| editor1-first=Andre | editor1-last=Maeder

| editor2-first=Philippe | editor2-last=Eenens

| publication-place=San Francisco | publisher=Astronomical Society of the Pacific

| page=144 | date=June 2004 | volume=215 | bibcode=2004IAUS..215..144D }}

{{citation | postscript=. | display-authors=1 | last1=Mason | first1=B. D. | last2=Wycoff | first2=G. L. I. | last3=Hartkopf | first3=W. I. | date=2008 | url=http://ad.usno.navy.mil/wds/ | accessdate=2017-09-15 | title=Washington Visual Double Star Catalog, 2006.5 (WDS) | publisher=U. S. Naval Observatory, Washington D.C. | archive-url=https://web.archive.org/web/20110214155533/http://ad.usno.navy.mil/wds/ | archive-date=2011-02-14 | url-status=dead }}

{{citation

| contribution=A Cycle-4 Survey of RS CVn Binary Systems

| display-authors=1 | last1=Redfield | first1=S.

| last2=Linsky | first2=J. L. | last3=Ayres | first3=T. R.

| last4=Brown | first4=A. | last5=Herczeg | first5=G. J.

| title=Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE ASP Conference Series, Vol. 348, Proceedings of the Conference held 2-6 August, 2004 in Victoria, British Columbia, Canada

| volume=348 | editor1-first=G. | editor1-last=Sonneborn | postscript=.

| editor2-first=H. | editor2-last=Moos

| editor3-first=B.-G. | editor3-last=Andersson

| page=269 | date=June 2006 | bibcode=2006ASPC..348..269R }}

{{citation

| title=Rotation, activity, and lithium abundance in cool binary stars

| last1=Strassmeier | first1=K. G. | last2=Weber | first2=M.

| last3=Granzer | first3=T. | last4=Järvinen | first4=S.

| display-authors=1 | postscript=.

| journal=Astronomische Nachrichten | arxiv=1208.3741

| volume=333 | issue=8 | page=663 | date=October 2012

| doi=10.1002/asna.201211719 | bibcode=2012AN....333..663S | s2cid=118450304 }}

{{cite journal |doi=10.1111/j.1365-2966.2004.07588.x

| 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 | issue=3 | pages=1069–1092

| bibcode=2004MNRAS.349.1069K |arxiv = astro-ph/0404219 | last1=Karataș

| first1=Yüksel

| last2=Bilir |first2=Selçuk

| last3=Eker |first3=Zeki

| last4=Demircan |first4=Osman

| last5=Liebert |first5=James

| last6=Hawley |first6=Suzanne L.

| last7=Fraser |first7=Oliver J.

| last8=Covey |first8=Kevin R.

| last9=Lowrance |first9=Patrick

| last10=Kirkpatrick |first10=J. Davy

| last11=Burgasser |first11=Adam J.

| year=2004

| doi-access=free | s2cid=15290475

}}

{{citation

| title=Spectrographic observations of Epsilon Ursae Minoris

| display-authors=1 | last1=Climenhaga | first1=J. L.

| last2=McKellar | first2=A. | last3=Petrie | first3=R. M.

| journal=Publications of the Dominion Observatory Ottawa

| volume=8 | pages=401–408 | date=November 1950

| bibcode=1950PDAO....8..401C | postscript=. }}

{{citation

| title=Eclipsing variables: Catalogue and classification

| display-authors=1 | last1=Avvakumova | first1=E. A.

| last2=Malkov | first2=O. Yu. | last3=Kniazev | first3=A. Yu.

| journal=Astronomische Nachrichten

| volume=334 | issue=8 | page=860 | date=October 2013

| doi=10.1002/asna.201311942 | bibcode=2013AN....334..860A | hdl=10995/27061 | hdl-access=free }}

{{citation

| display-authors=1 | last1=Pourbaix | first1=D.

| last2=Tokovinin | first2=A. A. | last3=Batten | first3=A. H.

| last4=Fekel | first4=F. C. | last5=Hartkopf | first5=W. I.

| last6=Levato | first6=H. | last7=Morrell | first7=N. I.

| last8=Torres | first8=G. | last9=Udry | first9=S.

| year=2004 | pages=727–732 | volume=424

| title=SB9: The Ninth Catalogue of Spectroscopic Binary Orbits

| journal=Astronomy & Astrophysics | issue=2 | postscript=.

| bibcode=2004A&A...424..727P | doi=10.1051/0004-6361:20041213 | arxiv=astro-ph/0406573| s2cid=119387088 }}

{{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

| arxiv=0806.2878 | s2cid=14878976 | postscript=. }}

{{citation

| last1=Nicolet | first1=B. | year=1978 | postscript=.

| title=Photoelectric photometric Catalogue of homogeneous measurements in the UBV System

| journal=Astronomy and Astrophysics Supplement Series

| volume=34 | pages=1–49 | bibcode=1978A&AS...34....1N }}

{{citation

| title=Ultraviolet Emission Lines in BA and Non-BA Giants

| display-authors=1 | last1=Böhm-Vitense | first1=Erika

| last2=Carpenter | first2=Kenneth G. | last3=Robinson | first3=Richard D.

| journal=The Astrophysical Journal | postscript=.

| volume=545 | issue=2 | pages=992–999 | date=December 2000

| doi=10.1086/317850 | bibcode=2000ApJ...545..992B | doi-access=free }}

{{cite simbad

| title=eps UMi | accessdate=2017-09-14 | postscript=. }}

{{citation | first1=R.H. | last1=Allen | title=Star Names: Their Lore and Meaning | date=1899 | url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Ursa_Minor*.html | page=459 }}

{{citation

| first=Jack W. | last=Rhoads

| title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars

| publisher=Jet Propulsion Laboratory, California Institute of Technology

| url=https://ntrs.nasa.gov/api/citations/19720005197/downloads/19720005197.pdf

| date=November 15, 1971 | postscript=. }}

}}