BG Indi

Light curves from TESS data for the two eclipsing binaries comprising BG Indi, adapted from Borkovits et al. (2021)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Indus
Right ascension 21h 58m 30.04050s[2]
Declination −59° 00′ 43.4938″[2]
Apparent magnitude (V) 6.141[3] (6.11 - 6.36)[4]
Characteristics
Spectral type F3V[5]
Variable type Algol[6]
Astrometry
Radial velocity (Rv)19.0 ± 0.5[7] km/s
Proper motion (μ) RA: 24.729 mas/yr
Dec.: 15.315[2] mas/yr
Parallax (π)19.5917 ± 0.2028 mas[2]
Distance166 ± 2 ly
(51.0 ± 0.5 pc)
Absolute magnitude (MV)2.45 / 3.02 / 7.23 / 7.83[1]
Absolute bolometric
magnitude (Mbol)		2.45 / 3.04 / 6.72 / 7.09[1]
Orbit[1]
PrimaryBG Ind A
CompanionBG Ind B
Period (P)720.9+3.4
−3.1 d yr
Semi-major axis (a)540.4+2.7
−2.2 R☉
Eccentricity (e)0.209+0.028
−0.048
Inclination (i)85.5+3.1
−6.3°
Periastron epoch (T)2458699+14
−21
Argument of periastron (ω)
(secondary)		1.6+9.2
−8.8°
Semi-amplitude (K1)
(primary)		12.57+0.17
−0.24 km/s
Semi-amplitude (K2)
(secondary)		26.02+0.31
−0.50 km/s
Orbit[1]
PrimaryBG Ind Aa
CompanionBG Ind Ab
Period (P)1.464065(2) d yr
Semi-major axis (a)7.602+0.038
−0.043 R☉
Eccentricity (e)0
Inclination (i)73.27+0.06
−0.13°
Periastron epoch (T)2458326.1362+0.0011
−0.0012[note 1]
Semi-amplitude (K1)
(primary)		120.47+1.12
−0.75 km/s
Semi-amplitude (K2)
(secondary)		130.99+0.48
−0.50 km/s
Orbit[1]
PrimaryBG Ind Ba
CompanionBG Ind Bb
Period (P)0.528349(2) d yr
Semi-major axis (a)3.025+0.011
−0.016 R☉
Eccentricity (e)0
Inclination (i)84.29+0.85
−0.87°
Periastron epoch (T)2458325.8072+0.0025
−0.0022[note 1]
Semi-amplitude (K1)
(primary)		138.98+1.23
−1.39 km/s
Semi-amplitude (K2)
(secondary)		149.25+1.09
−1.13 km/s
Details[1]
κ1 Ind Aa
Mass1.432+0.015
−0.024 M☉
Radius2.339+0.016
−0.021 R☉
Luminosity (bolometric)8.433+0.199
−0.169 L☉
Surface gravity (log g)3.852+0.011
−0.005 cgs
Temperature6442+29
−28 K
κ1 Ind Ab
Mass1.315+0.026
−0.023 M☉
Radius1.592+0.047
−0.019 R☉
Luminosity (bolometric)4.934+0.279
−0.179 L☉
Surface gravity (log g)4.150+0.007
−0.016 cgs
Temperature6816±26 K
κ1 Ind Ba
Mass0.688+0.008
−0.011 M☉
Radius0.642+0.005
−0.007 R☉
Luminosity (bolometric)0.167±0.009 L☉
Surface gravity (log g)4.660+0.003
−0.002 cgs
Temperature4609+48
−49 K
κ1 Ind Bb
Mass0.640+0.010
−0.011 M☉
Radius0.611+0.008
−0.009 R☉
Luminosity (bolometric)0.118±0.009 L☉
Surface gravity (log g)4.672±0.004 cgs
Temperature4327+62
−57 K
Other designations
κ1 Ind, BG Ind, CD−59° 7830, FK5 3752, HD 208496, HIP 108478, HR 8369, SAO 247247[6]
Database references
SIMBADdata

BG Indi, also known as κ1 Indi (Kappa1 Indi) is a multiple star system in the southern constellation of Indus. Its average apparent magnitude is 6.141,[3] meaning it can only be seen by the naked eye under exceptionally good viewing conditions. Stellar parallax measurements by Gaia put the system at about 166 light-years (51 parsecs) away.[2]

Nomenclature

The star system is most commonly known as BG Indi. BG Indi is its variable star designation, a unique name given to variable stars based on its constellation and when it was discovered to be a variable.[4] It also has the name κ1 Indi (Latinized to Kappa1 Indi), which is its Bayer designation.[6]

Properties

BG Indi consists of four stars in two compact, orbiting pairs. The brighter pair is known as BG Indi A, and consists of two F-type main-sequence stars Aa and Ab. As F-type stars, they are more massive, larger, and hotter than the Sun,[1] and with a metallicity of −0.2 ± 0.1, it is less metal-rich than the Sun. BG Indi is about 2.65 billion years old, and is just starting to leave the main sequence.[8]

BG Indi Aa and Ab orbit each other on a circular orbit, with a period of 1.46 days. Periodically, one star passes in front of the other, blocking its light. Therefore, the apparent magnitude varies from 6.11 to 6.36.[4] Its status as an eclipsing binary was confirmed by J. Manfroid and G. Mathys in 1984.[5]

The other two stars, BG Indi Ba and Bb, form the pair BG Indi B. Both are less massive than the Sun, and orbit each other on a tighter orbit with a period of 0.53 days. Collectively, BG Indi A and B orbit each other with a period of 720.9 days with a moderate eccentricity of 0.209. All three orbits are likely to be more or less coplanar. BG Indi is the nearest quadruple star system consisting of two eclipsing binaries.[1]

Notes

  1. 1 2 This refers to the epoch of primary transit.

References

  1. 1 2 3 4 5 6 7 8 9 Borkovits, T.; Rappaport, S. A.; Maxted, P F L.; Terentev, I.; Omohundro, M.; Gagliano, R.; Jacobs, T.; Kristiansen, M. H.; Lacourse, D.; Schwengeler, H. M.; Vanderburg, A.; Blackford, M. G. (2021). "BG Ind: The nearest doubly eclipsing, compact hierarchical quadruple system". Monthly Notices of the Royal Astronomical Society. 503 (3): 3759–3774. arXiv:2103.00925. doi:10.1093/mnras/stab621.
  2. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. 1 2 Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  4. 1 2 3 Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  5. 1 2 Manfroid, J.; Mathys, G. (1984). "The Bright Eclipsing Binary HD 208496". Information Bulletin on Variable Stars. 2616 (2616): 1. Bibcode:1984IBVS.2616....1M.
  6. 1 2 3 "* kap01 Ind". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-07-17.
  7. ↑ Holmberg, J.; Nordström, B.; Andersen, J. (2007). "The Geneva-Copenhagen survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk". Astronomy and Astrophysics. 475 (2): 519. arXiv:0707.1891. Bibcode:2007A&A...475..519H. doi:10.1051/0004-6361:20077221. S2CID 119054949.
  8. ↑ Rozyczka, M.; Kaluzny, J.; Pych, W.; Konacki, M.; Małek, K.; Mankiewicz, L.; Sokołowski, M.; Żarnecki, A. F. (2011). "Absolute properties of BG Ind - a bright F3 system just leaving the main sequence". Monthly Notices of the Royal Astronomical Society. 414 (3): 2479–2485. arXiv:1010.1355. Bibcode:2011MNRAS.414.2479R. doi:10.1111/j.1365-2966.2011.18567.x. S2CID 118422112.
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