Epsilon Cancri
{{Short description|Binary star system in the constellation Cancer}}
{{Starbox begin
| name = ε Cancri
}}
{{Starbox image
|image=
{{Location mark
|image=Cancer constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=8|mark_link=Epsilon Cancri
|x=507|y=456
}}
|caption=Location of ε Cancri (circled red)
}}
{{Starbox observe 2s
| epoch = J2000
| constell = Cancer
| component1 = ε Cnc A
| dec1 = {{DEC|19|32|41.3243}}
| component2 = HD 73711
| dec2 = {{DEC|19|31|55.1636}}
}}
{{Starbox character
| component1 = ε Cnc A
| class = A5 III{{cite journal | bibcode=1995ApJS...99..135A | title=The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars | journal=Astrophysical Journal Supplement | volume=99 | pages=135 | last1=Abt | first1=Helmut A. | last2=Morrell | first2=Nidia I. | year=1995 | doi=10.1086/192182 | doi-access=free }} {{nowrap|(kA3hA5mF0)}}
| component2 = HD 73711
| class2 = F0III{{cite journal | bibcode=2005yCat.3244....0G | title=VizieR Online Data Catalog: Catalog of Stellar Rotational Velocities (Glebocki+ 2005) | journal=VizieR On-line Data Catalog: III/244. Originally Published in: 2005csss...13..571G; 2005yCat.3244....0G | volume=3244 | last1=Glebocki | first1=R. | last2=Gnacinski | first2=P. | year=2005 }} {{nowrap|(kA3hA5mF0){{cite journal |bibcode=1986PASP...98..307A |title=MK classification of the brighter Praesepe stars |last1=Abt |first1=H. A. |journal=Publications of the Astronomical Society of the Pacific |year=1986 |volume=98 |page=307 |doi=10.1086/131757 |s2cid=122099889 }}}}
}}
{{Starbox astrometry
| component1 = ε Cnc A
| parallax = 5.3836
| p_error = 0.0474
| parallax_footnote = {{cite Gaia DR3|661291136701346304}}
| component2 = HD 73711
| radial_v2 =
| parallax2 = 5.4103
| p_error2 = 0.0308
| parallax_footnote2 = {{cite Gaia DR3|661290758744228224}}
| absmag_v2 =
}}
{{Starbox orbit
| primary = ε Cnc Aa
| name = ε Cnc Ab
| period_unitless = {{Val|35.14101|0.00005|u=d}}
| eccentricity = {{Val|0.4195|0.0003}}
| periastron = {{nowrap|2448314.598 ± 0.016}}
| periarg_primary = {{Val|258.38|0.02}}
| node = {{val|356.069|0.014}}
| inclination = {{val|81.454|0.010}}
| axis_unitless = {{val|1.9127|0.0004|u=mas}}
| k1 = {{Val|56.60|0.03}}
| k2 = {{Val|61.55|0.10}}
}}
{{Starbox detail
| component1 = ε Cnc Aa
| rotational_velocity = 49.2{{cite journal
| title=A photometric study of chemically peculiar stars with the STEREO satellites - II. Non-magnetic chemically peculiar stars
| display-authors=1
| last1=Paunzen | first1=E. | last2=Wraight | first2=K. T.
| last3=Fossati | first3=L. | last4=Netopil | first4=M.
| last5=White | first5=G. J. | last6=Bewsher | first6=D.
| journal=Monthly Notices of the Royal Astronomical Society
| volume=429 | issue=1 | pages=119–125 | date=February 2013
| doi=10.1093/mnras/sts318 | doi-access=free
| bibcode=2013MNRAS.429..119P
| arxiv=1211.1535 }}
| component2 = ε Cnc Ab
}}
{{Starbox detail|no_heading=y
| component1 = HD 73711
}}
{{Starbox catalog
| names = {{odlist | CCDM=J08404+1932 | WDS=J08405+1933 }}
| component1 = ε Cancri
| names1 = Meleph, {{odlist | B=ε Cnc | F=41 Cancri | BD=+20°2171 | HD=73731 | HIP=42556 | HR=3429 | SAO=98024 | GC=11904 | GSC=01395-02733 }}
| component2 = HD 73711
| names2 = {{odlist | BD=+20°2163 | HD=73711 | SAO=98018 | GC=11893 }}
}}
{{Starbox reference
| Simbad = Epsilon+Cancri|sn=ε Cancri
| Simbad2 = HD+73711|sn2=HD 73711
}}
{{Starbox end}}
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 (or Praesepe){{cite journal|bibcode=1995A&AS..113..419W|title=High-precision study of proper motions and membership of 924 stars in the central region of Praesepe|journal=Astronomy and Astrophysics Supplement|volume=113|pages=419|last1=Wang|first1=J. J|last2=Chen|first2=L|last3=Zhao|first3=J. H|last4=Jiang|first4=P. F|year=1995}} with an apparent visual magnitude of +6.29, which is near the lower limit of visibility with the naked eye. The annual parallax shift of {{val|5.4|ul=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{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=16 December 2017}}) and Ab. HD 73711 is also suspected of being a spectroscopic binary.{{cite journal|bibcode=1999ApJ...521..682A|title=Binaries in the Praesepe and Coma Star Clusters and Their Implications for Binary Evolution|doi=10.1086/307569|author=Abt, Helmut A.|author2= Willmarth, Daryl W.|journal=The Astrophysical Journal|volume=521|pages=682|number=2|year=1999|s2cid=119772785 |doi-access=free}}
Nomenclature
File:M44 Heggie.jpg. 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.{{cite web |url = http://www.ianridpath.com/startales/cancer.html#praesepe |title = Cancer – the asses and the Manger |website = Star Tales (online edition) |access-date = 2022-05-03}} In his Uranometria, Bayer cited (among others) the name Melleff or Meeleph for the cluster, from Arabic Al Ma'laf, the Stall; as Meleph, this name is also now applied specifically to this star.
In 2016, the IAU organized a Working Group on Star Names (WGSN){{cite web | url=https://www.iau.org/science/scientific_bodies/working_groups/280/ | title=IAU Working Group on Star Names (WGSN)|access-date=22 May 2016}} to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.{{cite web | url=https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf | page=5 | title=WG Triennial Report (2015–2018) – Star Names |access-date=2018-07-14}} 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.
Properties
The system is moving away from the Sun with a radial velocity of +30 km/s.
Epsilon Cancri A is a double-lined spectroscopic binary system with an orbital period of 35.14 days and eccentricity of 0.42. It has a stellar classification of A5 III, which matches an A-type giant star. The spectrum displays the chemically peculiar characteristics of an Am star.{{cite journal | last1=Renson | first1=P. | last2=Manfroid | first2=J. | title=Catalogue of Ap, HgMn and Am stars | journal=Astronomy and Astrophysics | volume=498 | issue=3 | pages=961–966 | date=May 2009 | doi=10.1051/0004-6361/200810788 | bibcode=2009A&A...498..961R | url=https://zenodo.org/record/890529 | doi-access=free }} Its spectral type has been listed as kA3hA5mF0, indicating the different spectral types shown by spectral lines of calcium, hydrogen, and other metals.{{cite journal|bibcode=1989ApJS...70..623G|title=The late A-type stars – Refined MK classification, confrontation with Stromgren photometry, and the effects of rotation|journal=Astrophysical Journal Supplement Series|volume=70|pages=623|last1=Gray|first1=R. O|last2=Garrison|first2=R. F|year=1989|doi=10.1086/191349|doi-access=free}} 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. The age of the system is estimated to be around 637 million years.
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.
References
{{reflist|refs=
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{{Stars of Cancer}}
{{DEFAULTSORT:Epsilon Cancri}}