Astronomy:Epsilon Chamaeleontis

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Short description: Star in the constellation Chamaeleon
ε Chamaeleontis
Chamaeleon constellation map.svg
Red circle.svg
Location of ε Cha on the map (circled)
Observation data
{{#ifeq:J2000.0 (ICRS)|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| [[History:Epoch|Epoch J2000.0 (ICRS)]]      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0 (ICRS)}}
Constellation Chamaeleon
A
Right ascension  11h 59m 37.58212s[1]
Declination −78° 13′ 18.5493″[1]
Apparent magnitude (V) 5.33±0.01[1]
B
Right ascension  11h 59m 37.51979s[1]
Declination −78° 13′ 18.9305″[1]
Apparent magnitude (V) 6.02±0.01[1]
Characteristics
A
Spectral type B9 Vn:[2]
U−B color index −0.16[3]
B−V color index −0.06[3]
B
Spectral type A[4]
B−V color index −0.05[1]
Astrometry
Radial velocity (Rv)+13±3.7[5] km/s
Proper motion (μ) RA: −40.34[6] mas/yr
Dec.: −8.30[6] mas/yr
Parallax (π)9.02 ± 0.36[6] mas
Distance360 ± 10 ly
(111 ± 4 pc)
Absolute magnitude (MV)−0.34[7]
Details
ε Cha Aa
Mass2.87[8] M☉
Radius2.3[9] R☉
Luminosity (bolometric)99.7[8] L☉
Temperature10,617±49[10] K
Rotational velocity (v sin i)265[11] km/s
Age2.8 Myr
Other designations
ε Cha, CPD−77° 772, GC 16402, HD 104174, HIP 58484, HR 4583, SAO 256894, CCDM J11596-7813AB, WDS J11596-7813AB[12]
Database references
SIMBADdata

Epsilon Chamaeleontis, Latinized from ε Chamaeleontis, is a triple star located in the southern circumpolar constellation Chamaeleon. The primary and secondary have apparent magnitudes of 5.33 and 6.02, making them visible to the naked eye. Hipparcos parallax measurements place the system at a distance of 360 light years[6] and is currently receding with a heliocentric radial velocity of 13 km/s.[5]

The primary has a stellar classification of B9 Vn:,[2] indicating that it is a B-type main-sequence star with broad/nebulous absorption lines due to rapid rotation. However, there is uncertainty behind the suffix.[2] It has 2.9 times the mass of the Sun[8] and 2.3 times its solar radius.[9] It radiates a bolometric luminosity 100 times that of the Sun[8] from its photosphere at an effective temperature of 10,617 K,[10] giving it a bluish-white hue. It is a relatively young star with an age of only 3 million years. Like many hot stars it spins rapidly, having a projected rotational velocity of 265 km/s.[11] 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.[citation needed]

The binary nature of this system was first observed during February 1836 when Sir John Herschel found it as the close double star, HJ 4486AB.[13] 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 et al. (1997).[14] It is a likely binary system, though no formal orbit has yet been determined.[4]

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 at least 36 stars.[15] 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.[16]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (March 2002). "The Tycho double star catalogue". Astronomy & Astrophysics 384 (1): 180–189. doi:10.1051/0004-6361:20011822. ISSN 0004-6361. Bibcode: 2002A&A...384..180F. 
  2. ↑ 2.0 2.1 2.2 Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations −90° to −53°. Bibcode: 1975mcts.book.....H. 
  3. ↑ 3.0 3.1 Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99–110. Bibcode: 1966CoLPL...4...99J. 
  4. ↑ 4.0 4.1 Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466–3471. doi:10.1086/323920. ISSN 0004-6256. Bibcode: 2001AJ....122.3466M. 
  5. ↑ 5.0 5.1 Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (November 2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten 328 (9): 889–896. doi:10.1002/asna.200710776. ISSN 0004-6337. Bibcode: 2007AN....328..889K. 
  6. ↑ 6.0 6.1 6.2 Template:Cite New HIP red.
  7. ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  8. ↑ 8.0 8.1 8.2 8.3 Fang, M.; van Boekel, R.; Bouwman, J.; Henning, Th.; Lawson, W. A.; Sicilia-Aguilar, A. (7 December 2012). "Young stars inϵChamaleontis and their disks: disk evolution in sparse associations". Astronomy & Astrophysics 549: 17. doi:10.1051/0004-6361/201118528. A15. ISSN 0004-6361. Bibcode: 2013A&A...549A..15F. 
  9. ↑ 9.0 9.1 Pasinetti Fracassini, L. E.; Pastori, L.; Covino, S.; Pozzi, A. (February 2001). "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) -Third edition -Comments and statistics". Astronomy and Astrophysics 367 (2): 521–524. doi:10.1051/0004-6361:20000451. ISSN 0004-6361. Bibcode: 2001A&A...367..521P. 
  10. ↑ 10.0 10.1 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. Bibcode: 2019AJ....158..138S. 
  11. ↑ 11.0 11.1 Huang, Su-Shu (September 1953). "A Statistical Study of the Rotation of the Stars.". The Astrophysical Journal 118: 285. doi:10.1086/145751. ISSN 0004-637X. Bibcode: 1953ApJ...118..285H. 
  12. ↑ "* eps Cha". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+eps+Cha. 
  13. ↑ Herschel, J. F. W. (1836). "Sixth Catalogue of Double Stars, observed at Slough, in the years 1831 and 1832, with the 20-fet Reflector; containing the Places, Descriptions, and Measured Angles of Position of 286 of those Objects, of which 105 have not been previously described. Reduced to the Epoch 1830·0". Memoirs of the Royal Astronomical Society 9: 193. Bibcode: 1836MmRAS...9..193H. 
  14. ↑ Horch, E.; Ninkov, Z.; Slawson, R. W.; van Altena, W. F.; Meyer, R. D.; Girard, T. M. (December 1997). "Speckle Imaging of Binary Stars with Large-Format CCDs". American Astronomical Society Meeting Abstracts 191: 44.02. Bibcode: 1997AAS...191.4402H. 
  15. ↑ Dickson-Vandervelde, D. Annie; Wilson, Emily C.; Kastner, Joel H. (28 January 2021). "Gaia-based Isochronal, Kinematic, and Spatial Analysis of the ϵ Cha Association". The Astronomical Journal 161 (2): 87. doi:10.3847/1538-3881/abd0fd. ISSN 0004-6256. Bibcode: 2021AJ....161...87D. 
  16. ↑ Jilinski, E.; Ortega, V. G.; de la Reza, R. (February 2005). "On the Origin of the Very Young Groups η and ε Chamaeleontis". The Astrophysical Journal 619 (2): 945–947. doi:10.1086/426535. ISSN 0004-637X. Bibcode: 2005ApJ...619..945J. 
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Further reading

External links



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