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]
Characteristics
Spectral type M4.55 III[4]
B−V color index 1.590±0.017[5]
Variable type SRb[6]
Astrometry
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)
(secondary)		212±22°
Semi-amplitude (K1)
(primary)		8.3±0.3 km/s
Details
Mass1.15±0.1[10] M☉
Radius59.8+15.1
−3.6[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
SIMBADdata

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]

References

  1. ↑ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  2. 1 2 3 4 5 6 7 8 9 10 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. 1 2 Otero, Sebastian Alberto (16 November 2009). "RR Ursae Minoris". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 May 2014.
  4. 1 2 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. 1 2 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. 1 2 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. 1 2 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. 1 2 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. 1 2 3 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. S2CID 120199240. 81.
  10. 1 2 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. 1 2 3 4 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. 1 2 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.
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