Epsilon Cancri

Epsilon Cancri (ε Cancri, abbreviated Epsilon Cnc, ε Cnc) is a white-hued binary star system in the zodiac constellation of Cancer. It is the brightest member of the Beehive Cluster[12] with an apparent visual magnitude of +6.29,[2] which is near the lower limit of visibility with the naked eye. The annual parallax shift of 5.3 mas as seen from Earth yields a distance estimate of approximately 616 light-years from the Sun.

ε Cancri
Location of ε Cancri (circled red)
Observation data
Epoch J2000      Equinox J2000
Constellation Cancer
Right ascension  08h 40m 27.01052s[1]
Declination 19° 32′ 41.3133″[1]
Apparent magnitude (V) 6.29[2]
Characteristics
Spectral type A5 III[3]
U−B color index +0.16[4]
B−V color index +0.17[4]
Astrometry
Radial velocity (Rv)+29.9±1.1[5] km/s
Proper motion (μ) RA: −36.301[6] mas/yr
Dec.: −12.291[6] mas/yr
Parallax (π)5.2937 ± 0.0781[6] mas
Distance616 ± 9 ly
(189 ± 3 pc)
Absolute magnitude (MV)+0.00[2]
Orbit[7]
Period (P)35.202±0.033 d
Eccentricity (e)0.32±0.04
Periastron epoch (T)2448313.5 ± 0.7
Argument of periastron (ω)
(secondary)		265±5°
Semi-amplitude (K1)
(primary)		53.0±1.9 km/s
Semi-amplitude (K2)
(secondary)		67.8±3.9 km/s
Details
Luminosity83.50[2] L☉
Temperature7,851[8] K
Metallicity [Fe/H]−0.01[9] dex
Rotational velocity (v sin i)82[10] km/s
Age729[11] Myr
Other designations
CCDM J08404+1932, WDS J08405+1933
ε Cancri: Meleph, ε Cnc, 41 Cancri, BD+20° 2171, GC 11904, HD 73731, HIP 42556, HR 3429, SAO 98024, GSC 01395-02733
HD 73711: Meleph, BD+20° 2163, GC 11893, HD 73711, SAO 98018
Database references
SIMBADε Cancri
HD 73711

The binary pair has the designation WDS J08405+1933. The primary star is designated Epsilon Cancri and the secondary is HD 73711. Epsilon Cancri is itself a spectroscopic binary with components designated Aa (also named Meleph[13]) and Ab. HD 73711 is itself suspected of being a spectroscopic binary.[14]

Nomenclature
The central stars of Praesepe. ε Cancri is the brightest star, left of centre (north is towards bottom right).

ε Cancri (Latinised to Epsilon Cancri) is the system's Bayer designation (which originally referred to the entire cluster[15]).

In 2016, the IAU organized a Working Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] It approved the name Meleph for the component Epsilon Cancri Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[13]

Properties

The system is moving away from the Sun with a radial velocity of +30 km/s.[5]

Epsilon Cancri A is a double-lined spectroscopic binary system with an orbital period of 35 days and eccentricity of 0.32.[7] It has a stellar classification of A5 III,[3] which matches an A-type giant star. The spectrum displays the chemically peculiar characteristics of an Am star.[18] Its spectral type has been listed as kA3hA5mF0, indicating the different spectral types shown by spectral lines of calcium, hydrogen, and other metals.[19] The age of the system is estimated to be around 729 million years.[11]

HD 73711 is another Am star F-type star with a stellar classification of F0 III.

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References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  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. Vizier catalog entry
  3. Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  4. Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". The Journal of the American Association of Variable Star Observers. 42 (2): 443. Bibcode:2014JAVSO..42..443M.Vizier catalog entry
  5. 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.
  6. 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.
  7. Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
  8. McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. Vizier catalog entry
  9. Gontcharov, G. A. (2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771–782. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031. Vizier catalog entry
  10. Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  11. Su, K. Y. L.; et al. (December 2006). "Debris Disk Evolution around A Stars". The Astrophysical Journal. 653 (1): 675–689. arXiv:astro-ph/0608563. Bibcode:2006ApJ...653..675S. doi:10.1086/508649.
  12. Wang, J. J; Chen, L; Zhao, J. H; Jiang, P. F (1995). "High-precision study of proper motions and membership of 924 stars in the central region of Praesepe". Astronomy and Astrophysics Supplement. 113: 419. Bibcode:1995A&AS..113..419W.
  13. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  14. Abt, Helmut A.; Willmarth, Daryl W. (1999). "Binaries in the Praesepe and Coma Star Clusters and Their Implications for Binary Evolution". The Astrophysical Journal. 521 (2): 682. Bibcode:1999ApJ...521..682A. doi:10.1086/307569.
  15. Ridpath, John Clark, ed. (1897). The standard American encyclopedia of arts, sciences, history, biography, geography, statistics, and general knowledge. 6. Encyclopedia publishing co. p. 2079.
  16. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  17. "WG Triennial Report (2015–2018) – Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  18. Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars" (PDF), Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
  19. Gray, R. O; Garrison, R. F (1989). "The late A-type stars – Refined MK classification, confrontation with Stromgren photometry, and the effects of rotation". Astrophysical Journal Supplement Series. 70: 623. Bibcode:1989ApJS...70..623G. doi:10.1086/191349.
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