RR Ursae Minoris

RR Ursae Minoris, or 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.[8] Based upon an annual parallax shift of 10.0 mas[1] 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.[6]

RR Ursae Minoris
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Minor
Right ascension  14h 57m 35.01625s[1]
Declination +65° 55′ 56.9143″[1]
Apparent magnitude (V) 4.44 - 4.85[2]
Characteristics
Spectral type M4.55 III[3]
B−V color index 1.590±0.017[4]
Variable type SRb[5]
Astrometry
Radial velocity (Rv)6.21±0.30[6] km/s
Proper motion (μ) RA: −82.191[1] mas/yr
Dec.: +26.981[1] mas/yr
Parallax (π)10.0206 ± 0.6341[1] mas
Distance330 ± 20 ly
(100 ± 6 pc)
Absolute magnitude (MV)−1.11[4]
Orbit[7]
Period (P)748.9 d
Eccentricity (e)0.13±0.05
Inclination (i)79.6±2.4[8]°
Longitude of the node (Ω)48.0±2.5[8]°
Periastron epoch (T)2,444,419±46 JD
Argument of periastron (ω)
(secondary)		212±22°
Semi-amplitude (K1)
(primary)		8.3±0.3 km/s
Details
Mass1.15±0.1[9] M☉
Radius103[10] R☉
Luminosity931.23[4] 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
SIMBADdata

This is a single-lined spectroscopic binary system with an orbital period of 2.05 years and an eccentricity of 0.13. The a sin i value is 8.4×107 km (0.56 AU),[7] where a is the semimajor axis and i is the orbital inclination to the line of sight from the Earth. The system is a source for X-ray and far-UV emission, with the latter most likely coming from the companion.[11]

The primary component is an aging red giant star on the asymptotic giant branch[11] with a stellar classification of M4.5 III.[3] It is a semiregular variable of subtype SRb,[5] ranging from magnitude 4.44 to 4.85 over a period of 43.3 days.[2] The interferometry-measured angular diameter of the primary component is 9.6±0.7 mas,[14] which, at its estimated distance, equates to a physical radius of about 103 times the radius of the Sun.[10]

References
  1. 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.
  2. Otero, Sebastian Alberto (16 November 2009). "RR Ursae Minoris". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 May 2014.
  3. 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.
  4. 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.
  5. 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.
  6. 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. A61.
  7. 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.
  8. 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.
  9. 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.
  10. Lang, Kenneth R. (2006). Astrophysical formulae. Astronomy and astrophysics library. 1 (3rd ed.). Birkhäuser. ISBN 3-540-29692-1. The radius (R*) is given by:
  11. 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.
  12. 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.
  13. "RR UMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 7, 2018.
  14. Richichi, A.; et al. (February 2005). "CHARM2: An updated Catalog of High Angular Resolution Measurements". Astronomy and Astrophysics. 431 (2): 773–777. Bibcode:2005A&A...431..773R. doi:10.1051/0004-6361:20042039.
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