Epsilon Cancri

Binary star system in the constellation Cancer From Wikipedia, the free encyclopedia

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[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.

Quick Facts Observation data Epoch J2000 Equinox J2000, Apparent magnitude (V) ...
ε Cancri
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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[1] mas/yr
Dec.: −12.133[1] mas/yr
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[3] mas/yr
Dec.: −12.118[3] mas/yr
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
ε Cnc Aa
Mass2.420[11] M
Radius4.8[4] R
Luminosity90[4] L
Surface gravity (log g)3.49[12] cgs
Temperature8,163[4] K
Metallicity [Fe/H]+0.10[12] dex
Rotational velocity (v sin i)49.2[13] km/s
Age637 ± 19[11] Myr
ε Cnc Ab
Mass2.226[11] M
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
Close

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

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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.[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

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