GJ 3991
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Hercules |
| Right ascension | 17h 09m 31.544s |
| Declination | +43° 40′ 52.77″ |
| Apparent magnitude (V) | 13.671 |
| Characteristics | |
| Spectral type | M3.5V |
| Apparent magnitude (B) | 13.46 |
| Apparent magnitude (R) | 11.511 |
| Apparent magnitude (J) | 7.380 |
| Apparent magnitude (H) | 6.76 |
| Apparent magnitude (K) | 6.485 |
| Astrometry | |
| Radial velocity (Rv) | −27.87 km/s |
| Proper motion (μ) | RA: +332.032 mas/yr Dec.: −274.501 mas/yr |
| Parallax (π) | 131.5996±0.4285 mas |
| Distance | 24.78 ± 0.08 ly (7.60 ± 0.02 pc) |
| Absolute magnitude (MV) | 12.41 |
| Orbit | |
| Period (P) | 14.7136±0.0005 days (0.0402836±0.0000014 yr) |
| Semi-major axis (a) | 0.015+0.01 −0.05" (0.1102 AU) |
| Eccentricity (e) | 0.068±0.004 |
| Argument of periastron (ω) (primary) | 175.0±3.0° |
| Semi-amplitude (K1) (primary) | 50.6±0.2 km/s |
| Details | |
| GJ 3991 A | |
| Mass | 0.20 M☉ |
| Temperature | 3250±50 K |
| Metallicity [Fe/H] | 0.20±0.06 dex |
| GJ 3991 B | |
| Mass | 0.50 M☉ |
| Temperature | ~4900 K |
| Age | >6? Gyr |
| Other designations | |
| GJ 3991, HIP 83945, G 203-47, WD 1708+437, USNO 752 | |
| Database references | |
| SIMBAD | data |
GJ 3991 (also known as Gliese 3991 and G 203-47) is a binary star system located 24.2 light-years away in the constellation Hercules. It consists of a red dwarf star with 20–30% the mass of the Sun, and a white dwarf star roughly 50% the mass of the sun. The two components orbit each other in a tight orbit only 0.11 astronomical units from each other, with an orbital period of only 14.71 days. Due to their small separation, the two objects have never been visually resolved and are merely predicted from the radial velocity changes of GJ 3991, making the system a spectroscopic binary.