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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-years eccentric orbit.[6]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 39m 51.87531s[1] |
| Declination | +11° 14′ 58.7029″[1] |
| Apparent magnitude (V) | 6.39[2] |
| Characteristics | |
| Evolutionary stage | main-sequence star |
| Spectral type | F8V[3] + M1±1V[4] |
| B−V color index | 0.559±0.006[2] |
| Astrometry | |
| Radial velocity (Rv) | −30.13±0.09[2] km/s |
| Proper motion (μ) | RA: +71.470±0.066[1] mas/yr Dec.: +89.165±0.076[1] mas/yr |
| Parallax (π) | 29.4076 ± 0.0272 mas[5] |
| Distance | 110.9 ± 0.1 ly (34.00 ± 0.03 pc) |
| Absolute magnitude (MV) | 3.76[2] |
| Orbit[6] | |
| Primary | HD 196885 A |
| Companion | HD 196886 B |
| Period (P) | 72.06 ± 4.59 yr |
| Semi-major axis (a) | 21.00 ± 0.86 AU |
| Eccentricity (e) | 0.42 ± 0.03 |
| Inclination (i) | 116.8 ± 0.7° |
| Longitude of the node (Ω) | 79.150° |
| Periastron epoch (T) | 1982.886 AD |
| Argument of periastron (ω) (secondary) | 231.464° |
| Details[6] | |
| A | |
| Mass | 1.3 ± 0.1 M☉ |
| Radius | 1.45+0.02 −0.05[citation needed] R☉ |
| Luminosity | 2.695±0.006[1] L☉ |
| Surface gravity (log g) | 4.46±0.02 cgs |
| Temperature | 6,340±39 K |
| Metallicity [Fe/H] | 0.29±0.05 dex |
| Rotation | 15 days[citation needed] |
| Rotational velocity (v sin i) | 7.3±1.5[citation needed] km/s |
| Age | 1.5—3.5 Gyr |
| B | |
| Mass | 0.45±0.01[6] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary star is near the lower limit of visibility to the naked eye with an apparent visual magnitude of 6.39.[2] It is located at a distance of 110.9 light years from the Sun.[5] 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.[2]
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.[8][4] It has a class in the range M1V to M3V[4] with 51% of the Sun's mass.[6]
The star BD+10 4351B, located 192 arcseconds away from HD 196885 is located at the same distance and may be a physically bound companion star, in which case HD 196885 is a trinary system.[9] If it is bound, then the separation is at least 6,600 AU (the separation along the line-of-sight is unknown, so this value represents a lower limit on the true separation).[citation needed]
In 2004, a planet was announced to be orbiting the star HD 196885 A in a 386-day orbit.[10] Follow-up work published in 2008 did not confirm the original candidate but instead found evidence of a planet in a 3.63 years.[11] Perturbation by the secondary star in this system may have driven the planet into a high inclination orbit.[12] The planetary existence was confirmed and parameters were refined by 2022.[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.98 ± 0.05 MJ | 2.6 ± 0.1 | 3.63 ± 0.01 | 0.48 ± 0.02 | — | — |
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