BG Indi
Star system
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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]
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] |
| Distance | 166 ± 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] | |
| Primary | BG Ind A |
| Name | BG Ind B |
| Period (P) | 720.9+3.4 −3.1 d |
| 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] | |
| Primary | BG Ind Aa |
| Name | BG Ind Ab |
| Period (P) | 1.464065(2) d |
| 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] | |
| Primary | BG Ind Ba |
| Name | BG Ind Bb |
| Period (P) | 0.528349(2) d |
| 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 | |
| Mass | 1.432+0.015 −0.024 M☉ |
| Radius | 2.339+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 |
| Temperature | 6442+29 −28 K |
| κ1 Ind Ab | |
| Mass | 1.315+0.026 −0.023 M☉ |
| Radius | 1.592+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 |
| Temperature | 6816±26 K |
| κ1 Ind Ba | |
| Mass | 0.688+0.008 −0.011 M☉ |
| Radius | 0.642+0.005 −0.007 R☉ |
| Luminosity (bolometric) | 0.167±0.009 L☉ |
| Surface gravity (log g) | 4.660+0.003 −0.002 cgs |
| Temperature | 4609+48 −49 K |
| κ1 Ind Bb | |
| Mass | 0.640+0.010 −0.011 M☉ |
| Radius | 0.611+0.008 −0.009 R☉ |
| Luminosity (bolometric) | 0.118±0.009 L☉ |
| Surface gravity (log g) | 4.672±0.004 cgs |
| Temperature | 4327+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 | |
| SIMBAD | data |
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
- This refers to the epoch of primary transit.