Astronomy:Epsilon Cancri

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Short description: Binary star system in the constellation Cancer
ε Cancri
Cancer constellation map.svg
Red circle.svg
Location of ε Cancri (circled red)
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|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[1] mas
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[3] mas
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 periapsis (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
ε Cancri: {{{names1}}}
HD 73711: {{{names2}}}
Database references
SIMBADε 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

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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.  Vizier catalog entry
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 4.2 4.3 Stassun, Keivan G. et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256. Bibcode: 2019AJ....158..138S. 
  5. ↑ 5.0 5.1 Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement 99: 135. doi:10.1086/192182. Bibcode: 1995ApJS...99..135A. 
  6. ↑ 6.0 6.1 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. doi:10.1086/191349. Bibcode: 1989ApJS...70..623G. 
  7. ↑ 7.0 7.1 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. ↑ 8.0 8.1 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. doi:10.1086/131757. Bibcode: 1986PASP...98..307A. 
  10. ↑ 10.0 10.1 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. doi:10.1051/0004-6361/201219219. A61. Bibcode: 2012A&A...546A..61D. 
  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 Morales, Leslie M.; Sandquist, Eric L.; Schaefer, Gail H.; Farrington, Christopher D.; Klement, Robert; Bedin, Luigi R.; Libralato, Mattia; Malavolta, Luca et al. (2022). "The Interferometric Binary ε Cnc in Praesepe: Precise Masses and Age". The Astronomical Journal 164 (2): 34. doi:10.3847/1538-3881/ac7329. Bibcode: 2022AJ....164...34M. 
  12. ↑ 12.0 12.1 Anders, F.; Khalatyan, A.; Queiroz, A. B. A.; Chiappini, C.; Ardevol, J.; Casamiquela, L.; Figueras, F.; Jimenez-Arranz, O. et al. (2022). "VizieR Online Data Catalog: StarHorse2, Gaia EDR3 photo-astrometric distances (Anders+, 2022)". Vizier Online Data Catalog. Bibcode: 2022yCat.1354....0A. 
  13. ↑ 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. doi:10.1093/mnras/sts318. Bibcode: 2013MNRAS.429..119P. 
  14. ↑ 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. 
  15. ↑ 15.0 15.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  16. ↑ 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. doi:10.1086/307569. Bibcode: 1999ApJ...521..682A. 
  17. ↑ "Cancer – the asses and the Manger". http://www.ianridpath.com/startales/cancer.html#praesepe. 
  18. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  19. ↑ "WG Triennial Report (2015–2018) – Star Names". p. 5. https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf. 
  20. ↑ Renson, P.; Manfroid, J. (May 2009). "Catalogue of Ap, HgMn and Am stars". Astronomy and Astrophysics 498 (3): 961–966. doi:10.1051/0004-6361/200810788. Bibcode: 2009A&A...498..961R. https://zenodo.org/record/890529. 



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