RU Ursae Minoris

{{short description|Star in the constellation Ursa Minor}}

{{Starbox begin

| name = RU Ursae Minoris

}}

{{Starbox image

| image = 250px

| caption = A light curve for RU Ursae Minoris, plotted from TESS data

}}

{{Starbox observe

| epoch = J2000

| constell = Ursa Minor

| ra = {{RA|13|38|56.8159}}

| dec = {{DEC|+69|48|11.1694}}

| appmag_v = 10 - 10.66

}}

{{Starbox character

| class = F0 IV/V + K5V

| b-v =

| u-b =

| variable =

}}

{{Starbox astrometry

| radial_v =

| prop_mo_ra = {{val|17.253|0.056}}

| prop_mo_dec = {{val|−5.004|0.049}}

| parallax = 3.5007

| p_error = 0.0317

| parallax_footnote =

| absmag_bol = 2.48 ± 0.12 (A)
5.37 ± 0.19 (B)

| absmag_v = 2.45 ± 0.12 (A)
5.88 ± 0.19 (B)

}}

{{Starbox orbit

| reference =

| periastron = JD 2441596.33645(6)

| period_unitless = 0.52492555(1) d

| axis_unitless = {{solar mass|3.99 ± 0.02}}

| inclination = 82.33 ± 0.05

}}

{{Starbox detail

| source = {{cite journal|bibcode=2008PASP..120..720L|doi=10.1086/589976|title=A Long-term Photometric Study of the Near-contact Binary RU Ursae Minoris|journal=Publications of the Astronomical Society of the Pacific|volume=120|issue=869|pages=720|year=2008|last1=Lee|first1=Jae Woo|last2=Kim|first2=Chun-Hwey|last3=Kim|first3=Seung-Lee|last4=Lee|first4=Chung-Uk|last5=Han|first5=Wonyong|last6=Koch|first6=Robert H.|doi-access=free}}

| component1=RU UMi A

| mass = 2.32 ± 0.07

| radius = 1.78 ± 0.02

| gravity = 4.30 ± 0.02

| temperature = 7200 ± 200

| luminosity = 7.63 ± 0.87

| component2 = RU UMi B

| mass2 = 0.76 ± 0.02

| radius2 = 1.14 ± 0.02

| gravity2 = 4.20 ± 0.02

| temperature2 = 4630 ± 200

| luminosity2 = 0.54 ± 0.10

}}

{{Starbox catalog

| names = {{odlist | 2MASS=J13385680+6948111 | BD=+70°751 | Gaia DR2=1686621699950649344 | TYC=4402-504-1 }}

}}

{{Starbox reference

| Simbad = RU+UMi

}}

{{Starbox end}}

RU Ursae Minoris is a binary star system in the constellation Ursa Minor. Its apparent magnitude ranges from 10 to 10.66 over 0.52 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=37387 |title=RU Ursae Minoris |author=Watson, Christopher |date=4 January 2010 |work=AAVSO Website|publisher=American Association of Variable Star Observers|accessdate=18 July 2015}}

Its component stars were calculated to be a primary star of spectral type F0IV/V and a secondary of spectral type K5V, both slightly more luminous than their spectral types indicate. The system is semidetached, as the secondary star is filling its Roche lobe and transferring matter to the primary.{{cite journal|title=A Photometric study of the near-contact system RU Ursae Minoris |author1=Manimanis, V. N. |author2=Niarchos, P. G. | journal=Astronomy and Astrophysics |volume=369 |issue=3 |pages=960–64 |date=2001|doi=10.1051/0004-6361:20010178 |bibcode=2001A&A...369..960M|doi-access=free }} The primary is between 2.2 and 2.3 times as massive as the Sun, with 1.8 times its radius and around 8 times its luminosity. The secondary has around 0.72 times the Sun's mass, 1.1 times its radius and between 0.58 and 0.86 times its luminosity.{{cite journal|title=The Near-Contact Binary RU Ursae Minoris |author1=Zhu, Li-Ying |author2=Qian, Sheng-Bang |author3=Xiang, Fu-Yuan | journal=Publications of the Astronomical Society of Japan | volume=58 |issue=2|pages= 361–66 |date=2006 |doi=10.1093/pasj/58.2.361|bibcode=2006PASJ...58..361Z|doi-access=free }}

The period the two take to orbit each other is decreasing very slowly (by approximately 0.15 seconds per year), suggesting the components are moving closer and will become a contact binary.