Astronomy:EI Cancri

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Short description: Star in the constellation Cancer

Coordinates: Sky map 08h 58m 15.194s, +19° 45′ 47.08″

EI Cancri
EI Cancri is located in the constellation Cancer
EI Cancri is located in the constellation Cancer
EI Cancri
Location of EI Cancri in the constellation Cancer

Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Cancer[1]
A
Right ascension  08h 58m 15.07493s[2]
Declination +19° 45′ 48.2581″[2]
Apparent magnitude (V) 13.93[3]
B
Right ascension  08h 58m 15.14813s[4]
Declination +19° 45′ 48.8367″[4]
Apparent magnitude (V) 13.75[3]
Characteristics
A
Spectral type M8Ve[5]
B
Spectral type M7V[6]
Astrometry
A
Radial velocity (Rv)13 ± 5[7] km/s
Proper motion (μ) RA: −767.060[2] mas/yr
Dec.: −100.176[2] mas/yr
Parallax (π)194.1443 ± 0.1228[2] mas
Distance16.80 ± 0.01 ly
(5.151 ± 0.003 pc)
B
Proper motion (μ) RA: −937.133 mas/yr
Dec.: −34.559 mas/yr
Parallax (π)196.2619 ± 0.1976[4] mas
Distance16.62 ± 0.02 ly
(5.095 ± 0.005 pc)
Details
A
Mass0.120±0.014[8] M☉
Radius0.136±0.020[9] R☉
Luminosity (bolometric)0.00135±0.00040[10] L☉
Temperature2,890±79[10] K
Metallicity [Fe/H]+0.08[9] dex
Rotation≤10.76[8] days
Rotational velocity (v sin i)16.70±0.64[11] km/s
B
Mass0.103±0.014[8] M☉
Radius0.119±0.021[9] R☉
Luminosity (bolometric)0.000937±0.000028[10] L☉
Temperature2,802±78[10] K
Rotation≤9.60[8] days
Rotational velocity (v sin i)16.70±0.64[11] km/s
Other designations
EI Cnc, GJ 1116, WDS J08582+1945AB, G 9-38, G 47-14, G 41-11, LP 426-40, LTT 12343, PLX 2144.03, GSC 01397-01138, 2MASS J08581519+1945470
A: Gaia DR2 660597997696173440, LHS 2076, NLTT 20638[12]
B: Gaia DR2 660597997697274752, LHS 2077, NLTT 20637[13]
Database references
SIMBADThe system
A
B

EI Cancri, also known as G 9-38 and GJ 1116, is a binary star system consisting of two M-type stars.[14] Located at a distance of 16.7 light-years, it is among the nearest star systems.[15]

This system consist of two very-low-mass stars that are orbiting each other at an assumed orbital separation of 7.0 astronomical units and an estimated period of 42 years.[16] Component A has an apparent magnitude 13.93,[3] 0.127 times the Sun's mass, 0.136 times the Sun's radius,[9] and 0.14% of the Sun's luminosity.[10] Component B has an apparent magnitude 13.75,[3] 0.111 times the Sun's mass, 0.119 times the Sun's radius,[9] and 0.09% of the Sun's luminosity.[10] At the very end of the main sequence, with spectral classifications of M8Ve[5] and M7V[6] respectively, their effective temperatures are below 3,000 K.[10] A 2015 search for a third star in the system has yielded inconclusive results.[17]

An ultraviolet band light curve showing several flares on EI Cancri, adapted from Pettersen (1985)[18]

In 1985, Bjørn Ragnvald Pettersen announced his discovery that the star shows very high stellar flare activity, with an average of five flares per hour.[18] It was given its variable star designation, EI Cancri, in 1987.[19]

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R  Constellation record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 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.
  3. ↑ 3.0 3.1 3.2 3.3 Lépine, Sébastien; Shara, Michael M. (2005-03-01). "A Catalog of Northern Stars with Annual Proper Motions Larger than 015 (LSPM-NORTH Catalog)" (in en). The Astronomical Journal 129 (3): 1483. doi:10.1086/427854. ISSN 1538-3881. Bibcode: 2005AJ....129.1483L. 
  4. ↑ 4.0 4.1 4.2 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.
  5. ↑ 5.0 5.1 Cowley, A. P.; Hartwick, F. D. A. (1982). "Studies of late-type dwarfs. III. Radial velocities and spectral characteristics for 74 stars." (in en). The Astrophysical Journal 253: 237–241. doi:10.1086/159628. ISSN 0004-637X. Bibcode: 1982ApJ...253..237C. 
  6. ↑ 6.0 6.1 Newton, Elisabeth R.; Charbonneau, David; Irwin, Jonathan; Berta-Thompson, Zachory K.; Rojas-Ayala, Barbara; Covey, Kevin; Lloyd, James P. (2013-12-12). "Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M Dwarfs". The Astronomical Journal 147 (1): 20. doi:10.1088/0004-6256/147/1/20. ISSN 0004-6256. Bibcode: 2014AJ....147...20N. 
  7. ↑ "G9-38". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=G9-38. 
  8. ↑ 8.0 8.1 8.2 8.3 Silverstein, Michele L.; Clarke, Tracy E.; Peters, Wendy M.; Polisensky, Emil; Villadsen, Jackie; Stone, Jordan M. (2025-12-11). "First Detection of an Ultracool Dwarf at 340 MHz: VLITE Observations of EI Cancri AB". arXiv:2512.11120 [astro-ph.SR].
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Cifuentes, C.; Caballero, J. A.; González-Payo, J.; Amado, P. J.; Béjar, V. J. S.; Burgasser, A. J.; Cortés-Contreras, M.; Lodieu, N. et al. (January 2025). "CARMENES input catalogue of M dwarfs. IX. Multiplicity from close spectroscopic binaries to ultra-wide systems". Astronomy and Astrophysics 693: A228. doi:10.1051/0004-6361/202452527. ISSN 0004-6361. Bibcode: 2025A&A...693A.228C. 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (2023). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets". The Astronomical Journal 165 (6): 267. doi:10.3847/1538-3881/acd1ec. Bibcode: 2023AJ....165..267H. 
  11. ↑ 11.0 11.1 Jeffers, S. V.; Schöfer, P.; Lamert, A.; Reiners, A.; Montes, D.; Caballero, J. A.; Cortés-Contreras, M.; Marvin, C. J. et al. (2018-06-01). "CARMENES input catalogue of M dwarfs - III. Rotation and activity from high-resolution spectroscopic observations" (in en). Astronomy & Astrophysics 614: A76. doi:10.1051/0004-6361/201629599. ISSN 0004-6361. 
  12. ↑ "G9-38A". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=G9-38A. 
  13. ↑ "G9-38B". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=G9-38B. 
  14. ↑ Vizier query: Name=G* 1116, Centre de Données astronomiques de Strasbourg, accessed 30 December 2012.
  15. ↑ Nearby Stars Catalog (NSC) , Planetary Habitability Laboratory, University of Puerto Rico at Arecibo accessed 31 December 2012.
  16. ↑ Li, Hua-Li et al. (September 2023). "White-light Superflare and Long-term Activity of the Nearby M7-type Binary EI Cnc Observed with GWAC System". The Astrophysical Journal 954 (2): 142. doi:10.3847/1538-4357/ace59b. Bibcode: 2023ApJ...954..142L. 
  17. ↑ Davison, Cassy L.; White, R. J.; Henry, T. J.; Riedel, A. R.; Jao, W-C.; Bailey Iii, J. I.; Quinn, S. N.; Cantrell, J. R. et al. (2015). "A 3D Search for Companions to 12 Nearby M-Dwarfs". The Astronomical Journal 149 (3): 106. doi:10.1088/0004-6256/149/3/106. Bibcode: 2015AJ....149..106D. 
  18. ↑ 18.0 18.1 Pettersen, B. R. (July 1985). "Discovery of flare activity on the low luminosity red dwarf system G9-38 AB". Astronomy & Astrophysics 148: 151–154. Bibcode: 1985A&A...148..151P. 
  19. ↑ Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Kireeva, N. N. (August 1987). "The 68th Name-List of Variable Stars". Information Bulletin on Variable Stars 3058: 1–30. Bibcode: 1987IBVS.3058....1K. 

Further reading



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