W Ursae Minoris

{{short description|Multiple star system in the constellation Ursa Minor}}

{{Starbox begin

|name = W Ursae Minoris

}}

{{Starbox image

| image = 250px

| caption = A visual band light curve for W Ursae Minoris, adapted from Devinney et al. (1970)

}}

{{Starbox observe

| epoch = J2000

| ra = {{RA|16|08|27.2728}}

| dec = {{DEC|+86|11|59.5511}}

| appmag_v = 8.51-9.59

| constell = Ursa Minor

}}

{{Starbox character

| class = A1/2V{{cite journal

| title=MK Classifications of some Northern Hemisphere Binary Systems

| last1=Hill | first1=G. | last2=Hilditch | first2=R. W.

| last3=Younger | first3=F. | last4=Fisher | first4=W. A.

| journal=Memoirs of the Royal Astronomical Society

| volume=79 | page=131 | year=1975

| bibcode=1975MmRAS..79..131H | display-authors=1 }} (A3V + G2IV){{cite journal

| title=Semidetached double-lined eclipsing binaries: Stellar parameters and rare classes

| last=Malkov | first=Oleg Yu

| journal=Monthly Notices of the Royal Astronomical Society

| volume=491 | issue=4 | pages=5489–5497 | date=February 2020

| doi=10.1093/mnras/stz3363 | bibcode=2020MNRAS.491.5489M | doi-access=free }}

| b-v =

| u-b =

| variable = Algol

}}

{{Starbox astrometry

| radial_v = {{val|−15.3|1.1}}

| prop_mo_ra = {{val|−12.128|0.057}}

| prop_mo_dec = {{val|15.934|0.058}}

| parallax = 2.4144

| p_error = 0.0315

| parallax_footnote =

| absmag_v =

}}

{{Starbox orbit

| reference = {{cite journal |bibcode=2020RAA....20...52S |title=Investigation of near-contact semi-detached binary WUMi through observations and evolutionary models |last1=Soydugan |first1=Faruk |last2=Soydugan |first2=Esin |last3=Aliçavuş |first3=Fahri |journal=Research in Astronomy and Astrophysics |year=2020 |volume=20 |issue=4 |page=052 |doi=10.1088/1674-4527/20/4/52 |arxiv=1912.03664 |s2cid=208920968 }}

| period_unitless = 1.7 days

| k1 = {{val|90.4|1.5}}

| k2 = {{val|196.6|2.6}}

| inclination = {{val|83.57|0.18}}

| eccentricity = 0

| axis_unitless = {{val|10.01|0.06|ul=solar radius}}

}}

{{Starbox detail

| source =

| component1 = Aa

| mass = {{val|3.22|0.08}}

| radius = {{val|9.63|0.04}}

| temperature = {{val|9310|90|fmt=commas}}

| luminosity = {{val|89|6}}

| gravity = {{val|3.83|0.02}}

| component2 = Ab

| mass2 = {{val|1.44|0.05}}

| radius2 = {{val|3.09|0.03}}

| temperature2 = {{val|5240|200|fmt=commas}}

| luminosity2 = {{val|6.5|1.3|1.1}}

| gravity2 = {{val|3.62|0.02}}

| age_myr2 = ≈400

}}

{{Starbox catalog

| names = {{odlist | HD=150265 | HIP=79069 | SAO=2692 }}

}}

{{Starbox reference

| Simbad = W+UMi

}}

{{Starbox end}}

W Ursae Minoris is an eclipsing binary star system in the constellation Ursa Minor. Its apparent magnitude ranges from 8.51 to 9.59 over 1.7 days as one star passes in front of the other relative to observers on Earth.{{cite web|url=http://www.aavso.org/vsx/index.php?view=detail.top&oid=37380 |title=W Ursae Minoris |author=Watson, Christopher |date=4 January 2010 |work=AAVSO Website|publisher=American Association of Variable Star Observers|accessdate=18 July 2015}} The combined spectrum of the system is A1/2V.

Slight changes in the orbital period suggest that there is a third component of the multiple star system, most likely a red dwarf, with an orbital period of {{val|62.2|3.9|u=years}}.{{cite journal | title=Period analysis of three close binary systems: TW And, TT Her and W UMi |author1=Kreiner, J. M. |author2=Pribulla, T. |author3=Tremko, J. |author4=Stachowski, G. S. |author5=Zakrzewski, B. | journal =Monthly Notices of the Royal Astronomical Society | volume = 383 | issue = 4 |pages= 1506–12|date=2008 |doi=10.1111/j.1365-2966.2007.12652.x |bibcode=2008MNRAS.383.1506K|doi-access=free }} Another study suggests that the third star has a minimum mass of {{solar mass|0.49}} and an orbit of about {{val|72|u=years}}.

The two main stars are currently thought to have masses of {{solar mass|3.2|link=y}} and {{solar mass|1.4}} respectively. Models of their evolution and mass transfer suggest that the secondary star was initially the more massive of the two and that it has lost mass to what is now the primary as well as losing mass completely from the system. The two stars have also spiralled in towards each other over the few hundred million years since they formed.