Epsilon Chamaeleontis

Epsilon Chamaeleontis, Latinized from ε Chamaeleontis, is a naked-eye star located in the constellation Chamaeleon and is known as the star HIP 58484, HR 4583, or HD 104174, which during February 1836 Sir John Herschel found as the close double star, HJ 4486AB. Distance is 111±4 pc (362±14 light years) from the Sun, whose absolute magnitude of −0.361 and has the combined visual magnitude of +4.88. Observations throughout the 20th Century have been slowly reducing, whose latest separation is 0.364 arcsec in position angle 211°, as determined on date 1997.0905 using CCD speckle interferometry by E.P. Horch (1997). It is a likely binary system, though no formal orbit has yet been determined.

ε Chamaeleontis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Chamaeleon
Right ascension  11h 59m 37.57634s[1]
Declination −78° 13′ 18.6179″[1]
Apparent magnitude (V) 4.91[2]
Characteristics
Spectral type B9V(n)[3]
U−B color index −0.16[2]
B−V color index −0.06[2]
Astrometry
Radial velocity (Rv)+13[4] km/s
Proper motion (μ) RA: −40.34[1] mas/yr
Dec.: −8.30[1] mas/yr
Parallax (π)9.02 ± 0.36[1] mas
Distance360 ± 10 ly
(111 ± 4 pc)
Absolute magnitude (MV)−0.34[5]
Details[6]
ε Cha A
Mass2.87 M☉
Luminosity (bolometric)99.7 L☉
Temperature10,500 K
Age2.7 Myr
Other designations
ε Cha, CPD−77° 772, HD 104174, HIP 58484, HR 4583, SAO 256894.[7]
Database references
SIMBADdata

Epsilon Chamaeleontis A or HJ 4486A is an B9Vn dwarf star with an effective temperature of 11000 Kelvin. Apparent visual magnitude of +5.3, and has a mass of 3.3 solar masses. Epsilon Chamaeleontis B or HJ 4486B is also a dwarf star of undetermined 'A' spectral type with an effective temperature of about 9600 Kelvin, being based on the lesser apparent visual magnitude of +6.1, and is about 3.0 solar masses. Observation of the spectrum show strong nebula lines, suggesting the stars are of a young age.

Both stars are members of Scorpius-Centaurus Association or the smaller portion known as the Lower Centaurus Crux subgroup. The double star forms the nucleus of the very young Epsilon Chamaeleontis stellar group which comprises about twenty stars. The nebulosity and star formation occurring in this region is currently a very important line of study in the southern hemisphere, whose proximity to the Sun is yielding new astrophysical information. Several papers have been published in the last few years on Lower Centaurus Crux subgroup of stars in the far southern constellations of Musca, Chamaeleon and Octans holding the south celestial pole.

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Johnson, H. L.; Iriarte, B.; Mitchell, R. I.; Wisniewskj, W. Z. (1999), "UBVRIJKL photometry of the bright stars", Commission Lunar and Planetary Laboratory, 4: 99, Bibcode:1966CoLPL...4...99J.
  3. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  5. 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.
  6. Fang, M.; et al. (January 2013), "Young stars in ɛ Chamaleontis and their disks: disk evolution in sparse associations" (PDF), Astronomy & Astrophysics, 549: 17, arXiv:1209.5832, Bibcode:2013A&A...549A..15F, doi:10.1051/0004-6361/201118528, A15.
  7. "* eps Cha". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-11.
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