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ε Cancri
	Location of ε Cancri (circled red)
Observation data; Epoch J2000 Equinox J2000
Constellation	Cancer
	ε Cnc A
Right ascension	08h 40m 27.01010s
Declination	19° 32′ 41.3243″
Apparent magnitude (V)	6.29
	HD 73711
Right ascension	08h 40m 18.09670s
Declination	19° 31′ 55.1636″
Apparent magnitude (V)	7.535
Characteristics
ε Cnc A
Spectral type	A5 III (kA3hA5mF0)
U−B color index	+0.16
B−V color index	+0.17
HD 73711
Spectral type	F0III (kA3hA5mF0)
Astrometry
ε Cnc A
Radial velocity (Rv)	+29.9±1.1 km/s
Proper motion (μ)	RA: −36.293 mas/yr ; Dec.: −12.133 mas/yr
Parallax (π)	5.3836 ± 0.0474 mas
Distance	606 ± 5 ly ; (186 ± 2 pc)
Absolute magnitude (MV)	+0.00
HD 73711
Proper motion (μ)	RA: −36.251 mas/yr ; Dec.: −12.118 mas/yr
Parallax (π)	5.4103 ± 0.0308 mas
Distance	603 ± 3 ly ; (185 ± 1 pc)
Orbit
Primary	ε Cnc Aa
Companion	ε Cnc Ab
Period (P)	35.14101±0.00005 d
Semi-major axis (a)	1.9127±0.0004 mas
Eccentricity (e)	0.4195±0.0003
Inclination (i)	81.454±0.010°
Longitude of the node (Ω)	356.069±0.014°
Periastron epoch (T)	2448314.598 ± 0.016
Argument of periastron (ω); (primary)	258.38±0.02°
Semi-amplitude (K1); (primary)	56.60±0.03 km/s
Semi-amplitude (K2); (secondary)	61.55±0.10 km/s
Details
ε Cnc Aa
Mass	2.420 M☉
Radius	4.8 R☉
Luminosity	90 L☉
Surface gravity (log g)	3.49 cgs
Temperature	8,163 K
Metallicity [Fe/H]	+0.10 dex
Rotational velocity (v sin i)	49.2 km/s
Age	637 ± 19 Myr
ε Cnc Ab
Mass	2.226 M☉
HD 73711
Mass	2.54 M☉
Radius	2.4 R☉
Luminosity	43.5 L☉
Surface gravity (log g)	4.09 cgs
Temperature	9,572 K
Metallicity [Fe/H]	+0.79 dex
Rotational velocity (v sin i)	56.3 km/s
Age	407 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: BD+20°2163, GC 11893, HD 73711, SAO 98018
Database references
SIMBAD	ε Cancri
	HD 73711

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^[14] 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 5.4 mas as seen from Earth yields a distance estimate of approximately 606 light-years from the Sun.

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^[15]) and Ab. HD 73711 is also suspected of being a spectroscopic binary.^[16]

Nomenclature

ε Cancri (Latinised to Epsilon Cancri) is the system's Bayer designation, which originally referred to the entire cluster.^[17]

In 2016, the IAU organized a Working Group on Star Names (WGSN)^[18] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.^[19] 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.^[15]

Properties

The system is moving away from the Sun with a radial velocity of +30 km/s.^[10]

Epsilon Cancri A is a double-lined spectroscopic binary system with an orbital period of 35.14 days and eccentricity of 0.42.^[11] It has a stellar classification of A5 III,^[5] which matches an A-type giant star. The spectrum displays the chemically peculiar characteristics of an Am star.^[20] Its spectral type has been listed as kA3hA5mF0, indicating the different spectral types shown by spectral lines of calcium, hydrogen, and other metals.^[6] Despite the spectral classification, evolutionary models suggest that the star is still on the main sequence, although at the very end of its hydrogen-burning life.^[1] The age of the system is estimated to be around 637 million years.^[11]

HD 73711 is another Am star, given a stellar classification of F0 III on the basis of its hydrogen absorption lines but a more complete classification of kA3hA5mF0. Although the spectral class would indicate that the star is a giant, models suggest that it is still fusing hydrogen in its core.^[3]

References

^ ^a ^b ^c ^d ^e ^f 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.
^ ^a ^b ^c 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
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m 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.
^ ^a ^b ^c ^d 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ ^a ^b 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
^ ^a ^b Glebocki, R.; Gnacinski, P. (2005). "VizieR Online Data Catalog: Catalog of Stellar Rotational Velocities (Glebocki+ 2005)". VizieR On-line Data Catalog: III/244. Originally Published in: 2005csss...13..571G; 2005yCat.3244....0G. 3244. Bibcode:2005yCat.3244....0G.
^ Abt, H. A. (1986). "MK classification of the brighter Praesepe stars". Publications of the Astronomical Society of the Pacific. 98: 307. Bibcode:1986PASP...98..307A. doi:10.1086/131757. S2CID 122099889.
^ ^a ^b 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.
^ ^a ^b ^c ^d ^e ^f Morales, Leslie M.; Sandquist, Eric L.; Schaefer, Gail H.; Farrington, Christopher D.; Klement, Robert; Bedin, Luigi R.; Libralato, Mattia; Malavolta, Luca; Nardiello, Domenico; Orosz, Jerome A.; Monnier, John D.; Kraus, Stefan; Le Bouquin, Jean-Baptiste; Anugu, Narsireddy; Ten Brummelaar, Theo; Davies, Claire L.; Ennis, Jacob; Gardner, Tyler; Lanthermann, Cyprien (2022). "The Interferometric Binary ε Cnc in Praesepe: Precise Masses and Age". The Astronomical Journal. 164 (2): 34. arXiv:2205.10690. Bibcode:2022AJ....164...34M. doi:10.3847/1538-3881/ac7329. S2CID 248986906.
^ ^a ^b 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.
^ 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.
^ 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.
^ ^a ^b "Naming Stars". IAU.org. Retrieved 16 December 2017.
^ 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. S2CID 119772785.
^ "Cancer – the asses and the Manger". Star Tales (online edition). Retrieved 2022-05-03.
^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
^ "WG Triennial Report (2015–2018) – Star Names" (PDF). p. 5. Retrieved 2018-07-14.
^ 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.