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Epsilon Cancri

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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[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−B color index +0.16[7]
B−V color 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 mas/yr[1]
Dec.: −12.133 mas/yr[1]
Parallax (π)5.3836±0.0474 mas[1]
Distance606 ± 5 ly
(186 ± 2 pc)
Absolute magnitude (MV)+0.00[2]
HD 73711
Proper motion (μ) RA: −36.251 mas/yr[3]
Dec.: −12.118 mas/yr[3]
Parallax (π)5.4103±0.0308 mas[3]
Distance603 ± 3 ly
(185 ± 1 pc)
Orbit[11]
Primaryε Cnc Aa
Companionε 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[11]
ε Cnc Aa
Mass2.420±0.008 M☉
Radius~3.8[a] R☉
Luminosity~59.8 L☉
Surface gravity (log g)~3.6 cgs
Temperature~8,060 K
Metallicity [Fe/H]~ +0.2 dex
Age637±19 Myr
ε Cnc Ab
Mass2.226±0.004 M☉
Radius~2.7[b] R☉
Surface gravity (log g)~4.0 cgs
Temperature~8,330 K
Metallicity [Fe/H]~ +0.2 dex
Age637±19 Myr
HD 73711
Mass2.54[3] M☉
Radius2.4[3] R☉
Luminosity43.5[3] L☉
Surface gravity (log g)4.09[3] cgs
Temperature9,572[3] K
Metallicity [Fe/H]+0.79[3] dex
Rotational velocity (v sin i)56.3[8] km/s
Age407[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
SIMBADε Cancri
HD 73711

Epsilon Cancri is a white-hued multiple star system in the zodiac constellation of Cancer. Its name is a Bayer designation that is Latinized from ε Cancri, and abbreviated Epsilon Cnc or ε Cnc. This is the brightest member of the Beehive Cluster (or Praesepe)[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 5.4 mas as seen from Earth yields a distance estimate of approximately 606 light-years (186 pc) from the Sun. The system is moving away from the Sun with a radial velocity of +30 km/s.[10]

The outer 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 also suspected of being a spectroscopic binary.[14]

Nomenclature

[edit]
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 Beehive Cluster.[15] In his Uranometria, Bayer cited (among others) the name Melleff or Meeleph for the cluster, from Arabic Al Ma'laf, the Stall;[16] as Meleph, this name is also now applied specifically to this star.[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.[13]

Properties

[edit]

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]

Notes

[edit]
  1. ^ Calculated using distance of 183.1 parsecs and estimated angular diameter of 0.000194 arcseconds (0.194 mas).
    183.1 • 0.000194 • 107.5 = 3.8 R☉
  2. ^ Calculated using distance of 183.1 parsecs and estimated angular diameter of 0.000136 arcseconds (0.136 mas).
    183.1 • 0.000136 • 107.5 = 2.7 R☉

References

[edit]
  1. ^ a b c d e 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.
  2. ^ 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. XHIP record for this object at VizieR.
  3. ^ a b c d e f g h i j k l 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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.
  7. ^ 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
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ a b c d Morales, Leslie M.; et al. (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.
  12. ^ Wang, J. J.; et al. (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. ^ a b "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. S2CID 119772785.
  15. ^ "Cancer – the asses and the Manger". Star Tales (online edition). Retrieved 2022-05-03.
  16. ^ Allen, Richard Hinckley (1899). Star Names: Their Lore and Meaning. pp. 112–113.
  17. ^ "IAU Catalog of Star Names". Retrieved 24 April 2025.
  18. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  19. ^ "WG Triennial Report (2015–2018) – Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  20. ^ 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.
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