Epsilon Cancri (ε Cancri, abbreviatedEpsilon Cnc,ε Cnc) is a white-huedbinary star system in thezodiacconstellation ofCancer. It is the brightest member of theBeehive Cluster (or Praesepe)[14] with anapparent visual magnitude of +6.29,[2] which is near the lower limit of visibility with the naked eye. The annualparallax shift of5.4 mas as seen from Earth yields a distance estimate of approximately 606 light-years from theSun.
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cancer |
| ε Cnc A | |
| Right ascension | 08h 40m 27.01010s[1] |
| Declination | 19° 32′ 41.3243″[1] |
| Apparent magnitude (V) | 6.29[2] |
| HD 73711 | |
| Right ascension | 08h 40m 18.09670s[3] |
| Declination | 19° 31′ 55.1636″[3] |
| Apparent magnitude (V) | 7.535[4] |
| Characteristics | |
| ε Cnc A | |
| Spectral type | A5 III[5](kA3hA5mF0)[6] |
| U−Bcolor index | +0.16[7] |
| B−Vcolor index | +0.17[7] |
| HD 73711 | |
| Spectral type | F0III[8](kA3hA5mF0)[9] |
| Astrometry | |
| ε Cnc A | |
| Radial velocity (Rv) | +29.9±1.1[10] km/s |
| Proper motion (μ) | RA: −36.293[1]mas/yr Dec.: −12.133[1]mas/yr |
| Parallax (π) | 5.3836±0.0474 mas[1] |
| Distance | 606 ± 5 ly (186 ± 2 pc) |
| Absolute magnitude (MV) | +0.00[2] |
| HD 73711 | |
| Proper motion (μ) | RA: −36.251[3]mas/yr Dec.: −12.118[3]mas/yr |
| Parallax (π) | 5.4103 ± 0.0308 mas[3] |
| Distance | 603 ± 3 ly (185 ± 1 pc) |
| Orbit[11] | |
| 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° |
| Periastronepoch (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[11] M☉ |
| Radius | 4.8[4] R☉ |
| Luminosity | 90[4] L☉ |
| Surface gravity (log g) | 3.49[12] cgs |
| Temperature | 8,163[4] K |
| Metallicity [Fe/H] | +0.10[12] dex |
| Rotational velocity (v sin i) | 49.2[13] km/s |
| Age | 637 ± 19[11] Myr |
| ε Cnc Ab | |
| Mass | 2.226[11] M☉ |
| HD 73711 | |
| Mass | 2.54[3] M☉ |
| Radius | 2.4[3] R☉ |
| Luminosity | 43.5[3] L☉ |
| Surface gravity (log g) | 4.09[3] cgs |
| Temperature | 9,572[3] K |
| Metallicity [Fe/H] | +0.79[3] dex |
| Rotational velocity (v sin i) | 56.3[8] km/s |
| Age | 407[3] 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 | |
The binary pair has the designation WDS J08405+1933. The primary star is designated Epsilon Cancri and the secondary isHD 73711. Epsilon Cancri is itself aspectroscopic binary with components designated Aa (also namedMeleph[15]) and Ab. HD 73711 is also suspected of being a spectroscopic binary.[16]
Nomenclature
edit
ε Cancri (Latinised toEpsilon Cancri) is the system'sBayer designation, which originally referred to the entireBeehive Cluster.[17] In hisUranometria, Bayer cited (among others) the nameMelleff orMeeleph for the cluster, from ArabicAl Ma'laf, the Stall;[18] asMeleph, this name is also now applied specifically to this star.[19]
In 2016, the IAU organized aWorking Group on Star Names (WGSN)[20] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[21] It approved the nameMeleph 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
editThe system is moving away from the Sun with aradial velocity of +30 km/s.[10]
Epsilon Cancri A is a double-lined spectroscopic binary system with anorbital period of 35.14 days andeccentricity of 0.42.[11] It has astellar classification of A5 III,[5] which matches anA-typegiant star. Thespectrum displays thechemically peculiar characteristics of anAm star.[22] 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 themain 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 hydrogenabsorption lines but a more complete classification of kA3hA5mF0. Although the spectral class would indicate that the star is agiant, models suggest that it is still fusing hydrogen in its core.[3]
References
edit- ^abcdefVallenari, 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 atVizieR.
- ^abcAnderson, 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
- ^abcdefghijklmVallenari, 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 atVizieR.
- ^abcdStassun, 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.
- ^abAbt, 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.
- ^abGray, 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.
- ^abMallama, 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
- ^abGlebocki, 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.
- ^abde 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.
- ^abcdefMorales, 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.
- ^abAnders, 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.
- ^ab"Naming Stars". IAU.org. Retrieved16 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). Retrieved2022-05-03.
- ^Allen, Richard Hinckley (1899).Star Names: Their Lore and Meaning. pp. 112–113.
- ^"IAU Catalog of Star Names". Retrieved24 April 2025.
- ^"IAU Working Group on Star Names (WGSN)". Retrieved22 May 2016.
- ^"WG Triennial Report (2015–2018) – Star Names"(PDF). p. 5. Retrieved2018-07-14.
- ^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.