HD 196885
Multiple star system in the constellation Delphinus
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HD 196885 is a binary star system in the northern constellation of Delphinus. It comprises a pair of stars, HD 196885 A and HD 196885 B, on a 69-year eccentric orbit. The primary star has one known planet.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Delphinus[1] |
| Right ascension | 20h 39m 51.87484s[2] |
| Declination | +11° 14′ 58.7002″[2] |
| Apparent magnitude (V) | 6.39[1] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | F8V[3] + M1±1V[4] |
| B−V color index | 0.559±0.006[1] |
| Astrometry | |
| Radial velocity (Rv) | −30.13±0.09[1] km/s |
| Proper motion (μ) | RA: +71.915 mas/yr[2] Dec.: +89.318 mas/yr[2] |
| Parallax (π) | 29.4076±0.0272 mas[2] |
| Distance | 110.9 ± 0.1 ly (34.00 ± 0.03 pc) |
| Absolute magnitude (MV) | 3.76[1] |
| Orbit[5]: 7 | |
| Primary | HD 196885 A |
| Name | HD 196886 B |
| Period (P) | 69.045+0.533 −0.111 yr |
| Semi-major axis (a) | 19.778+0.108 −0.019 AU |
| Eccentricity (e) | 0.417+0.001 −0.004 |
| Inclination (i) | 120.427° |
| Longitude of the node (Ω) | 79.150° |
| Periastron epoch (T) | 1982.886 AD |
| Argument of periastron (ω) (secondary) | 231.464° |
| Details | |
| A | |
| Mass | 1.3±0.1[5] M☉ |
| Radius | 1.38±0.01[6] R☉ |
| Luminosity | 2.611±0.007[2] L☉ |
| Surface gravity (log g) | 4.28±0.03[6] cgs |
| Temperature | 6,267+18 −16[6] K |
| Metallicity [Fe/H] | +0.29±0.05[5] dex |
| Rotation | 15[7] days |
| Rotational velocity (v sin i) | 7.3±1.5[7] km/s |
| Age | 1.5—3.5[5] Gyr |
| B | |
| Mass | 0.45±0.01[5] M☉ |
| Radius | 0.57±0.04[6] R☉ |
| Surface gravity (log g) | 4.58±0.06[6] cgs |
| Temperature | 3,549+121 −124[6] K |
| Other designations | |
| BD+10°4351, GC 28784, HD 196885, HIP 101966, HR 7907, SAO 106360, WDS J20399+1115, GCRV 12946, GSC 01092-01778, 2MASS J20395188+1114588[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Stellar properties
The primary star is near the lower limit of visibility to the naked eye with an apparent visual magnitude of 6.39.[1] It is located at a distance of 110.9 light-years from the Sun.[2] It is drifting closer with a radial velocity of −30 km/s, and is expected to come to within 52.5 light-years in 836,000 years.[1]
The secondary, component B, is a red dwarf star separated by 0.6 arcseconds from the primary star that was discovered in 2006 with NaCo at VLT.[9][4] It has a class in the range M1V to M3V[4] with 51% of the Sun's mass.[5]
The star BD+10 4351B, located 192 arcseconds away from HD 196885, was once thought to be a possible third component of the system,[10] but Gaia astrometry shows a smaller parallax, indicating that it is an unrelated background star.[11]
Planetary system
In 2004, an exoplanet, HD 196885 Ab, was announced to be orbiting the star HD 196885 A in a 386-day orbit.[12] Follow-up work published in 2008 did not confirm the original candidate but instead found evidence of a planet in a 3.63 years orbit.[7] Perturbation by the secondary star in this system may have driven the planet into a high inclination orbit.[13] The planetary existence was confirmed and parameters were refined by 2022.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 3.394+0.702 −0.264 MJ |
2.383+0.002 −0.004 |
3.485+0.001 −0.016 |
0.444+0.013 −0.005 |
143.041+6.572 −4.582° |
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