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RR Ursae Minoris
A light curve for RR Ursae Minoris, plotted from Hipparcos data [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Ursa Minor
Right ascension 14h 57m 35.01625s [2]
Declination +65° 55′ 56.9143″ [2]
Apparent magnitude (V) 4.44 - 4.85 [3]
Spectral type M4.55 III [4]
B−V color index 1.590±0.017 [5]
Variable type SRb [6]
Radial velocity (Rv)6.21±0.30 [7] km/s
Proper motion (μ) RA: −82.191 [2]  mas/ yr
Dec.: +26.981 [2]  mas/ yr
Parallax (π)10.0206 ± 0.6341  mas [2]
Distance330 ± 20  ly
(100 ± 6  pc)
Absolute magnitude (MV)−1.11 [5]
Orbit [8]
Period (P)748.9 d
Eccentricity (e)0.13±0.05
Inclination (i)79.6±2.4 [9]°
Longitude of the node (Ω)48.0±2.5 [9]°
Periastron epoch (T)2,444,419±46 JD
Argument of periastron (ω)
Semi-amplitude (K1)
8.3±0.3 km/s
Mass1.15±0.1 [10]  M
[2]  R
Luminosity756.7±54.4 [2]  L
Surface gravity (log g)0.00 [11]  cgs
Temperature3,464 [12]  K
Other designations
AAVSO 1456+66, RR UMi, BD+66°878, FK5 554, HD 132813, HIP 73199, HR 5589, SAO 16558 [13]
Database references

RR Ursae Minoris, abbreviated RR UMi, is a binary star [11] system in the northern circumpolar constellation of Ursa Minor. It can be viewed with the naked eye, typically having an apparent visual magnitude of around 4.710. [9] Based upon an annual parallax shift of 10.0  mas [2] as seen from Earth's orbit, it is located 330  light years away. The system is moving further from the Sun with a heliocentric radial velocity of +6 km/s. [7]

This star was found to have a variable radial velocity by J. H. Moore in 1910. It is a single-lined spectroscopic binary system with an orbital period of 2.05 years and an eccentricity (ovalness) of 0.13. The a sin i value is 84 Gm (0.56  AU), [8] where a is the semimajor axis and i is the orbital inclination to the line of sight from the Earth. This gives a lower bound on the physical size of the orbit. The system is a source for X-ray and far-UV emission, with the latter most likely coming from the companion. [11]

The visible component is an aging red giant star on the asymptotic giant branch [11] with a stellar classification of M4.5 III. [4] It was found to be a variable star by J. Ashbrook in 1946, [14] and is catalogued as a semiregular variable of subtype SRb [6] that ranges from magnitude 4.44 to 4.85 over a period of 43.3 days. [3] However, variations in the period have been observed on a time scale of 30–60 days. [15] The star has 1.15 [10] times the mass of the Sun and has expanded to 60 times the Sun's radius. [2] It is radiating 757 [2] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,464 K. [12]


  1. ^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  2. ^ a b c d e f g h i j Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv: 1804.09365. Bibcode: 2018A&A...616A...1G. doi: 10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. ^ a b Otero, Sebastian Alberto (16 November 2009). "RR Ursae Minoris". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 May 2014.
  4. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode: 1989ApJS...71..245K. doi: 10.1086/191373.
  5. ^ a b Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv: 1108.4971. Bibcode: 2012AstL...38..331A. doi: 10.1134/S1063773712050015. S2CID  119257644.
  6. ^ a b Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode: 2017ARep...61...80S. doi: 10.1134/S1063772917010085. S2CID  125853869.
  7. ^ a b de Bruijne, J. H. J.; Eilers, A.-C. (October 2012). "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project". Astronomy & Astrophysics. 546: 14. arXiv: 1208.3048. Bibcode: 2012A&A...546A..61D. doi: 10.1051/0004-6361/201219219. S2CID  59451347. A61.
  8. ^ a b Batten, A. H.; Fletcher, J. M. (July 1986). "A revised spectroscopic orbit for RR Ursae Minoris". Publications of the Astronomical Society of the Pacific. 98: 647–650. Bibcode: 1986PASP...98..647B. doi: 10.1086/131808.
  9. ^ a b c Ren, Shulin; Fu, Yanning (March 2013). "Hipparcos Photocentric Orbits of 72 Single-lined Spectroscopic Binaries". The Astronomical Journal. 145 (3): 7. Bibcode: 2013AJ....145...81R. doi: 10.1088/0004-6256/145/3/81. 81.
  10. ^ a b Halabi, Ghina M.; Eid, Mounib El (2015). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society. 451 (3): 2957. arXiv: 1507.01517. Bibcode: 2015MNRAS.451.2957H. doi: 10.1093/mnras/stv1141. S2CID  118707332.
  11. ^ a b c d Ortiz, Roberto; Guerrero, Martín A. (2016). "Ultraviolet emission from main-sequence companions of AGB stars". Monthly Notices of the Royal Astronomical Society. 461 (3): 3036. arXiv: 1606.09086. Bibcode: 2016MNRAS.461.3036O. doi: 10.1093/mnras/stw1547. S2CID  118619933.
  12. ^ a b Soubiran, Caroline; et al. (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591: A118. arXiv: 1605.07384. Bibcode: 2016A&A...591A.118S. doi: 10.1051/0004-6361/201628497. S2CID  119258214.
  13. ^ "RR UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 7, 2018.
  14. ^ Dettmar, R. -J.; Gieseking, F. (December 1983). "The intrinsically variable spectroscopic binary RR UMi". Astronomy and Astrophysics, Supplemental Series. 54: 541–543. Bibcode: 1983A&AS...54..541D.
  15. ^ Lloyd, C.; West, K. W. (May 1996). "Observations of Low-amplitude Late-Type Variables". Information Bulletin on Variable Stars. 4335: 1. Bibcode: 1996IBVS.4335....1L.