Epsilon Indi

Epsilon Indi
Location of ε Indi (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Indus
Right ascension 22h 03m 21.65363s[1]
Declination −56° 47′ 09.5228″[1]
Apparent magnitude (V) 4.674±0.006[2]
Characteristics
Spectral type K5V + T1 + T6[3]
U−B color index 1.00[4]
B−V color index 1.056±0.016[5]
Astrometry
ε Ind A
Radial velocity (Rv)−40.43±0.13[1] km/s
Proper motion (μ) RA: 3,966.661(86) mas/yr[1]
Dec.: −2,536.192(92) mas/yr[1]
Parallax (π)274.8431 ± 0.0956 mas[1]
Distance11.867 ± 0.004 ly
(3.638 ± 0.001 pc)
Absolute magnitude (MV)6.89[6]
ε Ind Ba/Bb
Parallax (π)270.6580 ± 0.6896 mas[7]
Distance12.05 ± 0.03 ly
(3.695 ± 0.009 pc)
Orbit[8]
Primaryε Ind Ba
Companionε Ind Bb
Period (P)11.0197 ± 0.0076 yr
Semi-major axis (a)661.58 ± 0.37 mas
(2.4058 ± 0.0040 au)
Eccentricity (e)0.54042 ± 0.00063
Inclination (i)77.082 ± 0.032°
Longitude of the node (Ω)147.959 ± 0.023°
Argument of periastron (ω)
(secondary)		328.27 ± 0.12°
Details[9]
ε Ind A
Mass0.782±0.023[10] M☉
Radius0.711±0.005 R☉
Luminosity0.21±0.02 L☉
Surface gravity (log g)4.63±0.01 cgs
Temperature4,649±84 K
Metallicity [Fe/H]−0.13±0.06 dex
Rotation35.732+0.006
−0.003 days[11]
Rotational velocity (v sin i)2.00 km/s
Age3.5+0.8
−1.0[8] Gyr
ε Ind Ba/Bb
MassBa: 66.92±0.36 MJup
Bb: 53.25±0.29[8] MJup
RadiusBa: ~0.080–0.081 R☉
Bb: ~0.082–0.083[12] R☉
LuminosityBa: 2.04×10−5 L☉
Bb: 5.97×10−6[8] L☉
Surface gravity (log g)Ba: 5.43–5.45
Bb: 5.27–5.33[12] cgs
TemperatureBa: 1,352–1,385 K
Bb: 976–1,011[12] K
Other designations
UGP 544, ε Ind, CD−57°8464, CPD−57°10015, FK5 825, GJ 845, HD 209100, HIP 108870, HR 8387, SAO 247287, LHS 67[13]
Database references
SIMBADThe system
A
Bab
Bab (as X-ray source)

Epsilon Indi, Latinized from ε Indi, is a star system located at a distance of approximately 12 light-years from Earth in the southern constellation of Indus. The star has an orange hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.674.[2] It consists of a K-type main-sequence star, ε Indi A, and two brown dwarfs, ε Indi Ba and ε Indi Bb, in a wide orbit around it.[14] The brown dwarfs were discovered in 2003. ε Indi Ba is an early T dwarf (T1) and ε Indi Bb a late T dwarf (T6) separated by 0.6 arcseconds, with a projected distance of 1460 AU from their primary star.

ε Indi A has one known planet, ε Indi Ab, with a mass of 6.31 Jupiter masses in an elliptical orbit with a period of about 171.3 years. ε Indi Ab is the second-closest Jovian exoplanet, after ε Eridani b. The ε Indi system provides a benchmark case for the study of the formation of gas giants and brown dwarfs.[11]

  1. ^ a b c d e Cite error: The named reference Gaia3a was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Paunzen was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference aaa505 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference aaa86 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference van Leeuwen2007 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference sci299_5612_1552 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Gaia3b was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Chen2022 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Rains2020 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference 2024ApJ...964..110L was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Feng2019 was invoked but never defined (see the help page).
  12. ^ a b c Cite error: The named reference aaa510 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Smith et al was invoked but never defined (see the help page).