HD 202206 is a binary star system in the southern constellation of Capricornus. With an apparent visual magnitude of +8.1,[2] it is too faint to be visible to the naked eye. It is located at a distance of 150 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +14.7 km/s.[5]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21h 14m 57.76850s[1] |
| Declination | −20° 47′ 21.1624″[1] |
| Apparent magnitude (V) | +8.07±0.01[2] |
| Characteristics | |
| Spectral type | G6V[3] + M8V[2] |
| B−V color index | 0.714±0.012[4] |
| Astrometry | |
| Radial velocity (Rv) | +14.68±0.23[5] km/s |
| Proper motion (μ) | RA: −39.079[1] mas/yr Dec.: −119.999[1] mas/yr |
| Parallax (π) | 21.7264 ± 0.0651 mas[1] |
| Distance | 150.1 ± 0.4 ly (46.0 ± 0.1 pc) |
| Absolute magnitude (MV) | +4.80[4] |
| Orbit[2] | |
| Period (P) | 256.33 days |
| Semi-major axis (a) | 1.40±0.10 mas |
| Eccentricity (e) | 0.432±0.001 |
| Inclination (i) | 10.9±0.8° |
| Longitude of the node (Ω) | 121±4° |
| Periastron epoch (T) | 2,452,176.14±0.12 JD |
| Argument of periastron (ω) (secondary) | 161.9±0.2° |
| Semi-amplitude (K1) (primary) | 0.567±0.001 km/s |
| Details | |
| A | |
| Mass | 1.07±0.08[2] M☉ |
| Radius | 1.05+0.02 −0.03[1] R☉ |
| Luminosity | 1.084+0.004 −0.005[1] L☉ |
| Surface gravity (log g) | 4.5±0.1[2] cgs |
| Temperature | 5,735+76 −74[1] K |
| Metallicity [Fe/H] | 0.29±0.01[4] dex |
| Rotational velocity (v sin i) | 2.3±0.5[2] km/s |
| Age | 2.9±1.0[2] Gyr |
| B | |
| Mass | 0.089+0.007 −0.006[2] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary component is a G-type main-sequence star with a stellar classification of G6V,[3] indicating it is generating energy through core hydrogen fusion. It is an estimated three[2] billion years old and is spinning with a projected rotational velocity of 2.3 km/s.[2] It is a metal-rich star – what astronomers term the abundance of elements of higher atomic number than helium – which may explain the star's unusually high luminosity for its class.[7] The star has a slightly greater mass and radius compared to the Sun.[2]
Companions edit
In 2000, analysis of radial velocity measurements of the star revealed the existence of a brown dwarf companion[8] with at least 17 times the mass of Jupiter around the star in an eccentric orbit with a period of around 256 days.[7] Even after the brown dwarf was accounted for, the star still showed a drift in the radial velocity measurements, suggesting another companion in a longer-period orbit. In 2004 after further observations, the parameters of a proposed companion was announced.[9]
Further observation of this system revised this picture in 2017, showing that the system instead consisted of a pair of co-orbiting stars being viewed nearly face-on, with the pair being orbited in turn by a Super-Jupiter designated HD 202206 c. The secondary stellar companion, now designated component B rather than 'b', is a red dwarf star with 8.9% of the mass of the Sun.[2]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| c | 17.9+2.9 −1.8 MJ |
2.41 | 1,260±11 | 0.22±0.03 | 7.7±1.1° | — |
References edit
- ^ a b c d e f g h 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.
- ^ a b c d e f g h i j k l m n Benedict, G. Fritz; Harrison, Thomas E. (June 2017). "HD 202206: A Circumbinary Brown Dwarf System". The Astronomical Journal. 153 (6): 12. arXiv:1705.00659. Bibcode:2017AJ....153..258B. doi:10.3847/1538-3881/aa6d59. S2CID 119105717. 258.
- ^ a b Houk, N.; Smith-Moore, M. (1988). Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Vol. 4. Bibcode:1988mcts.book.....H.
- ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ a b Valenti, Jeff A.; Fischer, Debra A. (2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500.
- ^ "HD 202206". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-07-05.
- ^ a b Udry, S.; et al. (2002). "The CORALIE survey for southern extra-solar planets VIII. The very low-mass companions of HD 141937, HD 162020, HD 168443, HD 202206: Brown dwarfs or "superplanets"?". Astronomy and Astrophysics. 390 (1): 267–279. arXiv:astro-ph/0202458. Bibcode:2002A&A...390..267U. doi:10.1051/0004-6361:20020685. S2CID 9389274.
- ^ "Exoplanets Galore!" (Press release). Garching, Germany: European Southern Observatory. April 15, 2000. Retrieved December 30, 2012.
- ^ Correia, A.; et al. (2005). "The CORALIE survey for southern extra-solar planets. XIII. A pair of planets around HD202206 or a circumbinary planet?". Astronomy and Astrophysics. 440 (2): 751–758. arXiv:astro-ph/0411512. Bibcode:2005A&A...440..751C. doi:10.1051/0004-6361:20042376. S2CID 16175663.
External links edit
- HD 202206 Archived 2012-05-27 at the Wayback Machine on Extrasolar Planets Encyclopaedia
- Extrasolar Planet Interactions by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona