GJ 3991

Gliese 3991
Observation data
Epoch J2000.0      Equinox 2015.5
Constellation Hercules
GJ 3991 A
Right ascension 17h 09m 32.018s[1]
Declination +43° 40′ 48.52″
Apparent magnitude (V) 13.671
GJ 3991 B
Right ascension 17h 09m 32.018s
Declination +43° 40′ 48.52″
Apparent magnitude (V) >15
Characteristics
GJ 3991 A
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
GJ 3991 B
Evolutionary stage White dwarf
Spectral type D?12
Astrometry
Radial velocity (Rv)−9.7±0.2 km/s
Total velocity17.971±0.199 km/s
Proper motion (μ) RA: 332.59±1.01[1] mas/yr
Dec.: −271.83±1.11 mas/yr
Parallax (π)131.5996 ± 0.4285 mas[2]
Distance24.78 ± 0.08 ly
(7.60 ± 0.02 pc)
Absolute magnitude (MV)14.316
Orbit[3]
PrimaryGJ 3991 B
CompanionGJ 3991 A
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
Mass0.20 M☉
Temperature3250±50 K
Metallicity1.584+0.235
−0.205 Fe/☉
Metallicity [Fe/H]0.20±0.06 dex
GJ 3991 B
Mass0.50 M☉
Temperature~4900 K
Age>6? Gyr
Other designations
G 203-47, Gliese 3991, HIP 83945, USNO 752
GJ 3991 A: G 203-47 A
GJ 3991 B: G 203-47 B, WD 1708+437
Database references
SIMBADdata

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 A, making the system a spectroscopic binary.

  1. ^ a b Lindegren, L.; et al. (25 April 2018). "Gaia Data Release 2: The astrometric solution". Astronomy & Astrophysics. A2: 616. arXiv:1804.09366. Bibcode:2018A&A...616A...2L. doi:10.1051/0004-6361/201832727. S2CID 54497421.
  2. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ^ Delfosse, Xavier; et al. (April 1999), "New neighbours. I. 13 new companions to nearby M dwarfs", Astronomy and Astrophysics, 344: 897–910, arXiv:astro-ph/9812008, Bibcode:1999A&A...344..897D.