Eta Coronae Borealis (η Coronae Borealis, η CrB) is a stellar system that lies approximately 58 light-years away. The primary component is a mid-wide binary, while a brown dwarf component is located at a wide separation.
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 23m 12.31s[1] |
| Declination | +30° 17′ 16.17″[1] |
| Apparent magnitude (V) | 5.02 |
| Characteristics | |
| Spectral type | G1V[2] / G3V[2] / L8 [3] |
| B−V color index | 0.56 |
| Astrometry | |
| Radial velocity (Rv) | -7.410 ± 0.054[4] km/s |
| Proper motion (μ) | RA: 116.83 ± 0.40[1] mas/yr Dec.: -171.37 ± 0.49[1] mas/yr |
| Parallax (π) | 55.98 ± 0.78 mas[1] |
| Distance | 58.3 ± 0.8 ly (17.9 ± 0.2 pc) |
| Orbit[4] | |
| Primary | Eta Coronae Borealis A |
| Companion | Eta Coronae Borealis B |
| Period (P) | 15189.1 ± 2.9 days |
| Semi-major axis (a) | 0.860 ± 0.003″ |
| Eccentricity (e) | 0.277 ± 0.001 |
| Inclination (i) | 58.7 ± 0.16° |
| Longitude of the node (Ω) | 22.9 ± 0.19° |
| Periastron epoch (T) | 1892.317 ± 0.031 |
| Argument of periastron (ω) (secondary) | 39.24 ± 0.37° |
| Argument of periastron (ω) (primary) | 219.2 ± 0.37° |
| Semi-amplitude (K1) (primary) | 4.709 ± 0.095 km/s |
| Semi-amplitude (K2) (secondary) | 5.276 ± 0.054 km/s |
| Position (relative to Eta Coronae Borealis AB)[3] | |
| Component | Eta Coronae Borealis C |
| Angular distance | 194″ |
| Position angle | 136° |
| Projected separation | ~3600 AU |
| Details | |
| Mass | 1.19 ± 0.071[4] / 1.05 ± 0.05[4] / 0.060 ± 0.015[3] M☉ |
| Metallicity [Fe/H] | -0.20[5] dex |
| Age | 1-2.5[3] Gyr |
| Other designations | |
2 Coronae Borealis, HD 137107/137108, HIP 75312, Gliese 584, HR 5727 | |
| Database references | |
| SIMBAD | data |
Components edit
Eta Coronae Borealis has been known since the late 18th century to be a moderate-separation binary. The orbit of the two components takes approximately 42 years, which when combined with the distance to the system makes the two stars fairly easily resolvable with a larger telescope. The two stars have similar physical parameters, though the secondary is slightly cooler than the primary and has approximately 90% of the primary's mass. Possible stable planetary orbits in the habitable zone were calculated for the system in 1996.[6]
At present the angular separation between both stars is 0.5 arcseconds, so a telescope with a diameter of over 25 centimetres is required to resolve it [1].
A brown dwarf companion was detected in 2001. The source 2MASSW J1523226+301456 in the 2MASS working database was identified as having a similar proper motion to the AB binary, and subsequent observations confirmed its relationship to the system. The new component, Eta Coronae Borealis C, was found to have a spectral type of L8. The brown dwarf has a minimum separation of 3600 AU, and considering a cooling age of 1–2.5 gigayears, the brown dwarf has a mass of 0.060 ± 0.015 M☉, or 63 ± 16 MJ.[3]
See also edit
References edit
- ^ a b c d e 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. S2CID 18759600.
- ^ a b Edwards, T. W. (1976). "MK classification for visual binary components". The Astronomical Journal. 81: 245. Bibcode:1976AJ.....81..245E. doi:10.1086/111879.
- ^ a b c d e Kirkpatrick, J. Davy; Dahn, Conard C.; Monet, David G.; Reid, I. Neill; et al. (2001). "Brown Dwarf Companions to G-Type Stars. I. Gliese 417B and Gliese 584C". The Astronomical Journal. 121 (6): 3235–3253. arXiv:astro-ph/0103218. Bibcode:2001AJ....121.3235K. doi:10.1086/321085. S2CID 18515414.
- ^ a b c d Pourbaix, D. (2000). "Resolved double-lined spectroscopic binaries: A neglected source of hypothesis-free parallaxes and stellar masses". Astronomy and Astrophysics Supplement Series. 145 (2): 215–222. Bibcode:2000A&AS..145..215P. doi:10.1051/aas:2000237.
- ^ Soderblom, D. R. (1983). "Rotational studies of late-type stars. II - Ages of solar-type stars and the rotational history of the sun". The Astrophysical Journal Supplement Series. 53: 1. Bibcode:1983ApJS...53....1S. doi:10.1086/190880.
- ^ Benest, D. (1996). "Planetary orbits in the elliptic restricted problem. III. The η Coronae Borealis system". Astronomy and Astrophysics. 314: 983–88. Bibcode:1996A&A...314..983B.