36 Ophiuchi
36 Ophiuchi (or Guniibuu for component A) is a triple star system 19.5 light-years from Earth. It is in the constellation Ophiuchus.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | A: 17h 15m 20.851s B: 17h 15m 20.978s C: 17h 16m 13.3624s |
| Declination | A: −26° 36′ 09.04″ B: −26° 36′ 10.18″ C: −26° 32′ 46.129″ |
| Apparent magnitude (V) | 5.08/5.03/6.34 |
| Characteristics | |
| Spectral type | K2 V/K1 V/K5 V |
| U−B color index | 0.51(AB)/1.04 |
| B−V color index | 0.85(AB)/1.16 |
| Variable type | C: RS CVn |
| Astrometry | |
| 36 Oph A | |
| Radial velocity (Rv) | −0.6 km/s |
| Proper motion (μ) | RA: −498.600±0.123 mas/yr Dec.: −1149.158±0.086 mas/yr |
| Parallax (π) | 168.0031 ± 0.1343 mas |
| Distance | 19.41 ± 0.02 ly (5.952 ± 0.005 pc) |
| 36 Oph B | |
| Radial velocity (Rv) | 0.0 km/s |
| Proper motion (μ) | RA: −465.861±0.111 mas/yr Dec.: −1141.168±0.073 mas/yr |
| Parallax (π) | 168.1303 ± 0.1081 mas |
| Distance | 19.40 ± 0.01 ly (5.948 ± 0.004 pc) |
| 36 Oph C | |
| Radial velocity (Rv) | −0.04±0.22 km/s |
| Proper motion (μ) | RA: −479.573±0.031 mas/yr Dec.: −1124.332±0.020 mas/yr |
| Parallax (π) | 167.9617 ± 0.0311 mas |
| Distance | 19.418 ± 0.004 ly (5.954 ± 0.001 pc) |
| Orbit | |
| Companion | 36 Ophiuchi B |
| Period (P) | 568.9 yr |
| Semi-major axis (a) | 14.7″ |
| Eccentricity (e) | 0.922 |
| Inclination (i) | 99.6° |
| Longitude of the node (Ω) | −83.6° |
| Periastron epoch (T) | 1,763.39 |
| Details | |
| 36 Oph A/B | |
| Mass | 0.85/0.85 M☉ |
| Radius | 0.817 ± 0.016/0.81 R☉ |
| Luminosity (bolometric) | 0.33/0.36 L☉ |
| Luminosity (visual, LV) | 0.28/0.30 L☉ |
| Temperature | 4,843 ± 134/4,985 ± 20 K |
| Metallicity | B: –0.31 ± 0.042 dex |
| Metallicity [Fe/H] | A: –0.20 dex |
| Age | 0.6-1.8 Gyr |
| 36 Oph C | |
| Mass | 0.71 M☉ |
| Radius | 0.72 R☉ |
| Luminosity (bolometric) | 0.20 L☉ |
| Luminosity (visual, LV) | 0.09 L☉ |
| Temperature | 4,550 K |
| Metallicity | 46–100% Sun |
| Other designations | |
36 Oph, WDS J17153-2636 | |
| AB: GJ 663, CD−26°12026, GCTP 3908.00, HIP 84405 | |
| A: Guniibuu, HR 6402, HD 155886, LHS 437, SAO 185198 | |
| B: HR 6401, HD 155885, LHS 438, SAO 185199 | |
| C: V2215 Ophiuchi, GJ 664, CD−26°12036, HD 156026, GCTP 3913.00, LHS 439, SAO 185213, HIP 84478 | |
| Database references | |
| SIMBAD | AB |
| A | |
| B | |
| C | |
| Exoplanet Archive | A |
| B | |
| C | |
| ARICNS | A |
| B | |
| C | |
36 Location of 36 Ophiuchi in the constellation Ophiuchus | |
The primary and secondary stars (also known as HD 155886) are nearly identical orange main-sequence dwarfs of spectral type K2/K1. This binary is unusual because its eruptions do not seem to conform to the Waldmeier effect; that is, the strongest eruptions of HD 155886 are not the ones characterized by the fast eruption onset. The tertiary star is an orange main-sequence dwarf of spectral type K5.
Star C is separated from the A-B pair by 700 arcseconds, compared to a minimum of 4.6 arcseconds for A-B, so its effect on the movements of the A-B pair is small. A and B have active chromospheres. At present the distance between the stars forming the AB-pair is 5.1 arcseconds and the position angle is 139 degrees, while star C is 731.6 arcseconds away from the A-component and situated at a position angle of 74 degrees.