CC Eridani

CC Eridani
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Eridanus
Right ascension 02h 34m 22.566s
Declination −43° 47′ 46.869″
Apparent magnitude (V) 8.70 to 9.05
Characteristics
Spectral type K7.5Ve + M3.5Ve
B−V color index 1.390±0.020
Variable type BY Dra + UV Cet
Astrometry
Radial velocity (Rv)41.9±0.9 km/s
Proper motion (μ) RA: 57.516 mas/yr
Dec.: −293.474 mas/yr
Parallax (π)86.6124±0.0355 mas
Distance37.66 ± 0.02 ly
(11.546 ± 0.005 pc)
Absolute magnitude (MV)8.57
Orbit
Period (P)1.56145 d
Eccentricity (e)0.0461
Inclination (i)40°–50°°
Argument of periastron (ω)
(secondary)		63.83°
Semi-amplitude (K1)
(primary)		41.94 km/s
Details
Primary
Mass0.57 M☉
Radius0.645 R☉
Secondary
Mass0.306 M☉
Radius0.41 R☉
Other designations
CC Eri, BD−44° 775, GC 3097, GJ 103, HD 16157, HIP 11964, SAO 215947, PPM 306855, LTT 1261
Database references
SIMBADdata

CC Eridani is a binary star system in the constellation of Eridanus. It varies in brightness from an apparent visual magnitude of 8.70 to 9.05 with a period of 1.56145 days. Based on parallax measurements, this system is located at distance of 37.7 light years from the Sun. It is drifting further away with a line of sight velocity component of 42 km/s, having come to within 20.9 light-years roughly 316,200 years ago.

Observations

This star became of interest because of its relatively high parallax, leading to a study of its radial velocity. In 1959, measurements by British astronomer D. S. Evans suggested it is a spectroscopic binary with a short period of 1.56146 days. It was found to vary in brightness and so was given the variable star designation CC Eri. The stellar classification of K7 Ve presented as a K-type main-sequence star with emission lines. Its light curve was found to vary strangely over time. By 1971, these variations were hypothesized to be due to large star spots on its surface.

In 1972, it was shown to be a flare star. It was theorized that all flare stars display spots, so the large feature on CC Eri modeled as spanning 5–20% of the surface and having a temperature 1,500 K cooler than the surrounding photosphere. This class of stars became known as BY Draconis variables. CC Eri was found to show periodic variation in its Hydrogen-alpha emission, which was close to the anti-phase of its brightness variation.

Observations with the ROSAT satellite showed that CC Eri varies in X-ray emission on time scales of minutes to a few hours. Radio observations were used to detect emission during flare events, while spectropolarimetry showed the presence of a strong magnetic field at the surface. Two X-ray super flare events were observed in 2017.

This is a spectroscopic binary star system with an orbital period of 1.56145 d. The primary component is co-rotating with the orbit, making it one of the most rapidly rotating K-type dwarfs in the Sun's neighborhood. It is a very active object, typically showing a one magnitude flare every 12 hours. CC Eri is a strong X-ray source. The primary has 57% of the Sun's mass and 65% of the radius of the Sun. The fainter secondary is a red dwarf with an estimated class of M3.5Ve. It has 31% of the mass and 41% of the radius of the Sun.

References

  1. 1 2 3 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  4. 1 2 3 4 5 6 Amado, P. J.; et al. (July 2000), "Rotational modulation and flares on RS CVn and BY Dra stars. XX. Photometry and spectroscopy of CC Eri in late 1989", Astronomy and Astrophysics, 359: 159–167, Bibcode:2000A&A...359..159A.
  5. 1 2 Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and Their Applications, Proceedings from IAU Symposium, 30, University of Toronto: International Astronomical Union: 57, Bibcode:1967IAUS...30...57E.
  6. 1 2 3 Evans, David S. (1959), "The dwarf binary HD 16157 : an interim report", Monthly Notices of the Royal Astronomical Society, 119: 526, Bibcode:1959MNRAS.119..526E, doi:10.1093/mnras/119.5.526.
  7. ↑ Leitzinger, M.; et al. (May 2026), Gopalswamy, N.; et al. (eds.), "Spectroscopic investigation of the southern late-K/early-M dwarf binary CC Eri", Proceedings of the International Astronomical Union, 20 (S388): 197–201, arXiv:2607.29316, Bibcode:2026IAUS..388..197L, doi:10.1017/S174392132400142X.
  8. ↑ "CC Eri", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-10-09.
  9. ↑ Bailer-Jones, C.A.L.; et al. (2018), "New stellar encounters discovered in the second Gaia data release", Astronomy & Astrophysics, 616: A37, arXiv:1805.07581, Bibcode:2018A&A...616A..37B, doi:10.1051/0004-6361/201833456, S2CID 56269929.
  10. ↑ "Stars, Parallax of : Stellar parallaxes determined photogrphically at the Cape Observatory (seventeenth list)", Monthly Notices of the Royal Astronomical Society, 110: 405, 1950, Bibcode:1950MNRAS.110..405., doi:10.1093/mnras/110.4.405. See p. 411.
  11. ↑ Evans, D. S. (1964), "The Strange Behaviour of CC Eridani", Monthly Notes of the Astronomical Society of Southern Africa, 23: 68, Bibcode:1964MNSSA..23...68E.
  12. ↑ Evans, D. S. (1971), "Star spots or grey veils? CC Eri and others", Monthly Notices of the Royal Astronomical Society, 154: 329, Bibcode:1971MNRAS.154..329E, doi:10.1093/mnras/154.3.329.
  13. ↑ Nather, R. E.; Harwood, J. (1972), "CC Eridani", IAU Circular, 2434, Bibcode:1972IAUC.2434....1N.
  14. ↑ Bopp, B. W.; Evans, D. S. (1973), "The spotted flare stars BY Dra and CC Eri: a model for the spots and some astrophysical implications", Monthly Notices of the Royal Astronomical Society, 164: 343–356, Bibcode:1973MNRAS.164..343B, doi:10.1093/mnras/164.4.343.
  15. ↑ Busko, I. C.; et al. (September 1977), "Hα Variability in CC Eri", Astronomy and Astrophysics, 60 (2): L27–L28, Bibcode:1977A&A....60L..27B.
  16. ↑ Pan, H. C.; Jordan, C. (January 1995), "ROSAT observations of the flare star CC ERI", Monthly Notices of the Royal Astronomical Society, 272 (1): 11–23, arXiv:astro-ph/9409044, Bibcode:1995MNRAS.272...11P, doi:10.1093/mnras/272.1.11.
  17. ↑ Osten, Rachel A.; et al. (January 2002), "Multiwavelength Observations of Three Short-Period Active Binary Systems: ER Vulpeculae, CC Eridani, and EI Eridani", The Astrophysical Journal Supplement Series, 138 (1): 99–120, Bibcode:2002ApJS..138...99O, doi:10.1086/323666.
  18. ↑ Slee, O. B.; et al. (2004), "A Multiwavelength Study of CC Eridani", Publications of the Astronomical Society of Australia, 21 (1): 72–81, Bibcode:2004PASA...21...72S, doi:10.1071/AS03034.
  19. ↑ Karmakar, Subhajeet; et al. (May 2017), "X-Ray Superflares on CC Eri", The Astrophysical Journal, 840 (2), id. 102, arXiv:1705.06930, Bibcode:2017ApJ...840..102K, doi:10.3847/1538-4357/aa6cb0.

Further reading