HD 217786
HD 217786 is a binary star[4] system in the equatorial constellation of Pisces. With an apparent visual magnitude of 7.78,[2] it requires binoculars or a small telescope to view. The system is located at a distance of 181 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +10 km/s.[2] Kinematically, the star system belongs to the thin disk population of the Milky Way.[7]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pisces |
| Right ascension | 23h 03m 08.20704s[1] |
| Declination | −00° 25′ 46.6777″[1] |
| Apparent magnitude (V) | 7.78[2] |
| Characteristics | |
| Spectral type | F8V[3] |
| B−V color index | 0.578±0.004[2] |
| Astrometry | |
| Radial velocity (Rv) | +10.00±0.02[2] km/s |
| Proper motion (μ) | RA: −89.933[1] mas/yr Dec.: −168.781[1] mas/yr |
| Parallax (π) | 17.9946 ± 0.0793[1] mas |
| Distance | 181.3 ± 0.8 ly (55.6 ± 0.2 pc) |
| Absolute magnitude (MV) | 4.09[2] + 11.02±0.13[4] |
| Details[5] | |
| A | |
| Mass | 1.02 M☉ |
| Radius | 1.32±0.06 R☉ |
| Luminosity | 1.93±0.04[6] L☉ |
| Surface gravity (log g) | 4.13±0.02 cgs |
| Temperature | 5,882±8[7] K |
| Metallicity | −0.19±0.01 |
| Rotational velocity (v sin i) | 1.18±0.05 km/s |
| Age | 9.40±0.22 Gyr |
| HD 217786 B | |
| Mass | 0.1622+0.0071 −0.0068[4] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary is an F-type main-sequence star with a stellar classification of F8V. It is much older than Sun with an estimated age of 9.4 billion years and is spinning slowly with a projected rotational velocity of 1.2 km/s. The star has a lower proportion of heavy elements than the Sun, having 65% of solar abundance.[7] It has about the same mass as the Sun but a 32% larger radius.[5] The star is radiating nearly double[6] the luminosity of the Sun from its photosphere at an effective temperature of 5,882 K.[7]
A low-mass stellar companion at a projected separation of 155 AU was discovered in 2016.[4] The proper motion of this co-moving object suggests it is gravitationally-bound to the primary, and their orbit is being viewed edge-on. If the orbit is assumed to be circular, then the orbital period for the pair is ~6.2 Myr.[4] No other companion stars have been detected at separations from 2.74 to 76.80 AUs.[6]
The star system exhibits strong stellar flare activity in the ultraviolet.[9]
Planetary system
In 2010 one superjovian planet or brown dwarf on an eccentric orbit was discovered utilising the radial velocity method.[10] Designated component Ab, the high eccentricity of this object may have been caused by interaction with the secondary star.[4]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| Ab | ≥13.0±0.8 MJ | 2.38±0.04 | 1,320±4 | 0.40±0.05 | — | — |
References
- 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.
- 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
- Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H
- Ginski, C.; et al. (2016), "A lucky imaging multiplicity study of exoplanet host stars – II", Monthly Notices of the Royal Astronomical Society, 457 (2): 2173–2191, arXiv:1601.01524, Bibcode:2016MNRAS.457.2173G, doi:10.1093/mnras/stw049, S2CID 53626523
- Quarles, Billy; Li, Gongjie; Kostov, Veselin; Haghighipour, Nader (2020), "Orbital Stability of Circumstellar Planets in Binary Systems", The Astronomical Journal, 159 (3): 80, arXiv:1912.11019, Bibcode:2020AJ....159...80Q, doi:10.3847/1538-3881/ab64fa, S2CID 209444271
- Wittrock, Justin M.; Kane, Stephen R.; Horch, Elliott P.; Howell, Steve B.; Ciardi, David R.; Everett, Mark E. (2017), "Exclusion of Stellar Companions to Exoplanet Host Stars", The Astronomical Journal, 154 (5): 184, arXiv:1709.05315, Bibcode:2017AJ....154..184W, doi:10.3847/1538-3881/aa8d69, S2CID 55789971
- Maldonado, J.; Villaver, E. (2017), "Searching for chemical signatures of brown dwarf formation", Astronomy & Astrophysics, 602: A38, arXiv:1702.02904, Bibcode:2017A&A...602A..38M, doi:10.1051/0004-6361/201630120, S2CID 56225222
- "HD 217786". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 29 September 2020.
- Shkolnik, Evgenya L. (2013), "An Ultraviolet Investigation of Activity on Exoplanet Host Stars", The Astrophysical Journal, 766 (1): 9, arXiv:1301.6192, Bibcode:2013ApJ...766....9S, doi:10.1088/0004-637X/766/1/9, S2CID 118415788
- Moutou, C.; et al. (2011), "The HARPS search for southern extra-solar planets", Astronomy & Astrophysics, 527: A63, arXiv:1012.3830, doi:10.1051/0004-6361/201015371, S2CID 118696125