Struve 2398
Location of Struve 2398 in the constellation Draco | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Struve 2398 A | |
| Right ascension | 18h 42m 46.70439s |
| Declination | +59° 37′ 49.4095″ |
| Apparent magnitude (V) | 8.94 |
| Struve 2398 B | |
| Right ascension | 18h 42m 46.89467s |
| Declination | +59° 37′ 36.7212″ |
| Apparent magnitude (V) | 9.70 |
| Characteristics | |
| Spectral type | M3 V + M3.5 V |
| U−B color index | 1.11/1.14 |
| B−V color index | 1.53/1.59 |
| Variable type | Flare star |
| Astrometry | |
| Struve 2398 A | |
| Radial velocity (Rv) | −1.30±0.12 km/s |
| Proper motion (μ) | RA: –1311.679 mas/yr Dec.: +1792.325 mas/yr |
| Parallax (π) | 283.8401±0.0220 mas |
| Distance | 11.4908 ± 0.0009 ly (3.5231 ± 0.0003 pc) |
| Absolute magnitude (MV) | +11.18 |
| Struve 2398 B | |
| Radial velocity (Rv) | 0.88±0.15 km/s |
| Proper motion (μ) | RA: –1400.264 mas/yr Dec.: +1862.525 mas/yr |
| Parallax (π) | 283.8378 ± 0.0287 mas |
| Distance | 11.491 ± 0.001 ly (3.5231 ± 0.0004 pc) |
| Absolute magnitude (MV) | +12.01 |
| Orbit | |
| Period (P) | 1,166±60 years |
| Semi-major axis (a) | 63±1 AU |
| Eccentricity (e) | 0.4396±0.0038 |
| Inclination (i) | 73.8±0.3° |
| Longitude of the node (Ω) | 145.32±0.37° |
| Periastron epoch (T) | 1837±4 |
| Argument of periastron (ω) (secondary) | 321.3±4.2° |
| Details | |
| Struve 2398 A | |
| Mass | 0.330±0.008 M☉ |
| Radius | 0.351±0.003 R☉ |
| Luminosity | 0.01552±0.00007 L☉ |
| Surface gravity (log g) | 4.87±0.01 cgs |
| Temperature | 3,433±68 K |
| Metallicity [Fe/H] | −0.23±0.08 dex |
| Rotation | 103.1±6.1 days |
| Rotational velocity (v sin i) | < 2.5 km/s |
| Age | 6.2±2.3 Gyr |
| Struve 2398 B | |
| Mass | 0.25±0.02 M☉ |
| Radius | 0.280±0.005 R☉ |
| Luminosity | 0.021 L☉ |
| Surface gravity (log g) | 4.41 cgs |
| Temperature | 3,379±31 K |
| Metallicity [Fe/H] | −0.30±0.08 dex |
| Rotation | 135±15 days |
| Rotational velocity (v sin i) | < 2.5 km/s |
| Age | 2.4 Gyr |
| Other designations | |
| Σ 2398, BD+59°1915, GJ 725 A/B, ADS 11632, GCTP 4330.00 A/B | |
| Struve 2398 A: Vyssotsky 184, HD 173739, HIP 91768, G 227-046, LHS 58 | |
| Struve 2398 B: HD 173740, HIP 91772, G 227-047, LHS 59 | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
| Exoplanet Archive | data |
Struve 2398 (Gliese 725) is a binary star system in the northern constellation of Draco. Struve 2398 is star number 2398 in the Struve Double Star Catalog of Russian-German astronomer Friedrich Georg Wilhelm von Struve. The astronomer's surname, and hence the star identifier, is sometimes indicated by a Greek sigma, Σ; hence, this system can be listed with the identifier Σ 2398. Although the components are too faint to be viewed with the naked eye, this star system is among the closest to the Sun. Parallax measurements by the Gaia spacecraft give them an estimated distance of 11.5 light-years (3.5 parsecs) away.
Both stars are small red dwarfs, with each having around a third the Sun's mass and radius. They each display the type of variability common to flare stars, and their active surfaces are sources of X-ray emission. They are orbiting with a period of about 871 years, at a separation of about 63 astronomical units with an orbital eccentricity of 0.29.
The pair has a relatively high proper motion of 2.2 arc seconds per year. The system is on an orbit through the Milky Way that has an eccentricity of 0.05, carrying them as close as 8 kpc and as far as 9 kpc from the Galactic Center. The plane of their galactic orbit carries them as far as 463−489 pc away from the galactic plane.