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 mas[6]
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
Mass2.5[8] M☉
Radius4.8[9] R☉
Luminosity90[9] L☉
Surface gravity (log g)3.49[8] cgs
Temperature8,163[9] K
Metallicity [Fe/H]+0.10[8] dex
Rotational velocity (v sin i)49.2[10] km/s
Age728[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
Praesepe. ε Cancri is the brightest blue star, near the centre of the image.

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 728 million years.

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

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. S2CID 18759600. 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. S2CID 119257644. 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, S2CID 59451347, 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, S2CID 119387088.
  8. Anders, F.; Khalatyan, A.; Queiroz, A. B. A.; Chiappini, C.; Ardevol, J.; Casamiquela, L.; Figueras, F.; Jimenez-Arranz, O.; Jordi, C.; Monguio, M.; Romero-Gomez, M.; Altamirano, D.; Antoja, T.; Assaad, R.; Cantat-Gaudin, T.; Castro-Ginard, A.; Enke, H.; Girardi, L.; Guiglion, G.; Khan, S.; Luri, X.; Miglio, A.; Minchev, I.; Ramos, P.; Santiago, B. X.; Steinmetz, M. (2022). "VizieR Online Data Catalog: StarHorse2, Gaia EDR3 photo-astrometric distances (Anders+, 2022)". Vizier Online Data Catalog. Bibcode:2022yCat.1354....0A.
  9. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
  10. Paunzen, E.; et al. (February 2013), "A photometric study of chemically peculiar stars with the STEREO satellites - II. Non-magnetic chemically peculiar stars", Monthly Notices of the Royal Astronomical Society, 429 (1): 119–125, arXiv:1211.1535, Bibcode:2013MNRAS.429..119P, doi:10.1093/mnras/sts318.
  11. 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. S2CID 118345778. Vizier catalog entry
  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. "Cancer – the asses and the Manger". Star Tales (online edition). Retrieved 2022-05-03.
  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", 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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