RS Canum Venaticorum

RS Canum Venaticorum is a binary star system in the northern constellation of Canes Venatici. It serves as the prototype to the class of RS Canum Venaticorum variables.[9] The peak apparent visual magnitude of this system is below the level needed to observe it with the naked eye. It is located at a distance of approximately 443 light years from the Sun based on parallax,[1] but is drifting closer with a net radial velocity of −14 km/s.[7] Olin J. Eggen (1991) included this system as a member of the IC 2391 supercluster,[5] but it was later excluded.[12]

RS Canum Venaticorum
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Canes Venatici
Right ascension 13h 10m 36.90788s[1]
Declination +35° 56′ 05.5877″[1]
Apparent magnitude (V) 7.93[2]
Characteristics
A
Evolutionary stage Main-sequence[3]
Spectral type F6IV[4] or F5V[3]
B−V color index 0.46[5]
B
Evolutionary stage Subgiant[3]
Spectral type G8IV[4] or K2IV[3]
B−V color index 0.91[5]
Variable type Eclipsing and RS CVn[6]
Astrometry
Radial velocity (Rv)−13.62±0.44[7] km/s
Proper motion (μ) RA: −49.974[1] mas/yr
Dec.: +20.576[1] mas/yr
Parallax (π)7.3606 ± 0.0408[1] mas
Distance443 ± 2 ly
(135.9 ± 0.8 pc)
Absolute magnitude (MV)2.95[8]
Orbit[9]
Period (P)4.797695 d
Eccentricity (e)0.00[10]
Inclination (i)85.55°
Periastron epoch (T)2,448,379.1993 HJD
Semi-amplitude (K1)
(primary)		90.2±0.1 km/s
Semi-amplitude (K2)
(secondary)		84.3 km/s
Details[9]
A
Mass1.44[5] M☉
Radius2.1 R☉
Temperature6,800 K
Rotation8.542 d
Rotational velocity (v sin i)11±2 km/s
Age2.5 Gyr
B
Mass1.31[5] M☉
Radius4.3 R☉
Temperature4,580 K
Rotational velocity (v sin i)42±3 km/s
Other designations
RS CVn, BD−36°2344, GJ 9430, HD 114519, HIP 64293, SAO 63382, WDS J13106+3556[11]
Database references
SIMBADdata

The variable nature of this system was discovered by the Russian astronomer Lidiya Tseraskaya in 1914.[6] It is a detached binary in a close, circular orbit with a period of 4.8 days.[9] The orbital plane is inclined by an angle of 85.55° to the line of sight from the Earth, causing this to be viewed from Earth as an eclipsing binary. The primary eclipse minimum decreases the visual magnitude of the system by 1.21, while the secondary minimum decreases the magnitude by 0.26.[2]

The primary component is a relatively inactive F-type main-sequence star[3] with a stellar classification of F5V. It has 2.1 times the radius of the Sun with a projected rotational velocity of about 11 km/s. That rate is slower than expected if the rotation of the star were locked with its orbital period. It has an estimated age of 2.5 billion years.[3]

The secondary component is a magnetically active K-type subgiant star with a class of K2 IV.[3] It has 4.3 times the Sun's radius and a relatively high rotation rate with a projected rotational velocity of 42 km/s.[9] This rapid spin was likely driven by interaction with the primary, and it generates the surface magnetic activity that makes the star variable.[13] As with the Sun, it is undergoing differential rotation.[9]

Lower temperature starspots cover a significant fraction of the secondary's surface, causing light variation as the star rotates.[14] These are found at several active latitudes on the star below 70°, and appear to migrate at the rate of 0.1° per day.[9] The total amount of spots varies in intensity with a cycle of 19.7±1.9 years, ranging from 17% to 37% coverage of the surface.[10] The luminosity also varies slightly (0.01) due to proximity and reflection from the primary star.[3] X-ray emission has been detected from this star with a luminosity of 2.14×1031 erg s−1.[9] It has also been detected in the radio band.[15]

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. Malkov, O. Yu.; et al. (February 2006), "A catalogue of eclipsing variables", Astronomy and Astrophysics, 446 (2): 785–789, Bibcode:2006A&A...446..785M, doi:10.1051/0004-6361:20053137
  3. Messina, S. (March 2008), "Long-term magnetic activity in close binary systems. I. Patterns of color variations", Astronomy and Astrophysics, 480 (2): 495–508, arXiv:0712.2117, Bibcode:2008A&A...480..495M, doi:10.1051/0004-6361:20078932, S2CID 117824595
  4. Strassmeier, K. G.; Fekel, F. C. (1990), "The spectral classification of chromospherically active binary stars with composite spectra", Astronomy and Astrophysics, 230: 389, Bibcode:1990A&A...230..389S
  5. Eggen, O. J. (December 1991), "The IC 2391 Supercluster", Astronomical Journal, 102: 2028, Bibcode:1991AJ....102.2028E, doi:10.1086/116025
  6. Sitterly, Bancroft Walker (1930), "The Eclipsing Variable RS Canum Venaticorum", Contributions from the Princeton University Observatory, 11: 21−41, Bibcode:1930CoPri..11...21S
  7. Karataș, Yüksel; Bilir, ‪Selçuk; Eker, Zeki; Demircan, Osman; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser, Adam J. (2004). "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution". Monthly Notices of the Royal Astronomical Society. 349 (3): 1069–1092. arXiv:astro-ph/0404219. Bibcode:2004MNRAS.349.1069K. doi:10.1111/j.1365-2966.2004.07588.x. S2CID 15290475.
  8. 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
  9. Xiang, Yue; et al. (March 2020), "The first Doppler imaging of the active binary prototype RS Canum Venaticorum", Monthly Notices of the Royal Astronomical Society, 492 (3): 3647–3656, arXiv:2001.02572, Bibcode:2020MNRAS.492.3647X, doi:10.1093/mnras/staa063
  10. Rodono, M.; et al. (September 1995), "Starspot evolution, activity cycle and orbital period variation of the prototype active binary RS Canum Venaticorum.", Astronomy and Astrophysics, 301: 75, Bibcode:1995A&A...301...75R
  11. "RS CVn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-11-05.
  12. Eggen, Olin J. (December 1995), "Reality Tests of Superclusters in the Young Disk Population", Astronomical Journal, 110: 2862, Bibcode:1995AJ....110.2862E, doi:10.1086/117734
  13. Percy, John R. (May 24, 2007), Understanding Variable Stars, Cambridge University Press, p. 90, ISBN 9781139463287
  14. Eaton, Joel A.; et al. (September 1993), "Spots on RS CVn From Spectroscopy and Photometry", Astronomical Journal, 106: 1181, Bibcode:1993AJ....106.1181E, doi:10.1086/116717
  15. Boboltz, D. A.; et al. (July 2003), "Astrometric Positions and Proper Motions of 19 Radio Stars", The Astronomical Journal, 126 (1): 484–493, arXiv:astro-ph/0303503, Bibcode:2003AJ....126..484B, doi:10.1086/375462, S2CID 119455647

Further reading
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