Struve 2398 AB
Struve 2398 is located in the constellation Draco.
Struve 2398 is located in the constellation Draco.
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[1]
Declination +59° 37′ 49.4095″[1]
Apparent magnitude (V) 8.94[2]
Struve 2398 B
Right ascension 18h 42m 46.89467s[3]
Declination +59° 37′ 36.7212″[3]
Apparent magnitude (V) 9.70
Characteristics
Spectral type M3 V + M3.5 V[4]
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[1] km/s
Proper motion (μ) RA: –1311.679 mas/yr[1]
Dec.: +1792.325 mas/yr[1]
Parallax (π)283.8401 ± 0.0220 mas[1]
Distance11.4908 ± 0.0009 ly
(3.5231 ± 0.0003 pc)
Struve 2398 B
Radial velocity (Rv)0.88±0.15[3] km/s
Proper motion (μ) RA: –1400.264 mas/yr[3]
Dec.: +1862.525 mas/yr[3]
Parallax (π)283.8378 ± 0.0287 mas[3]
Distance11.491 ± 0.001 ly
(3.5231 ± 0.0004 pc)
Details
Struve 2398 A
Mass0.336±0.007[5] M☉
Radius0.354±0.003[5] R☉
Luminosity0.01511±0.00019[5] L☉
Temperature3,401+18
−17[5] K
Metallicity [Fe/H]−0.23±0.08[4] dex
Rotational velocity (v sin i)< 2.5[6] km/s
Age3.0[4] Gyr
Struve 2398 B
Mass0.248±0.025[4] M☉
Radius0.273±0.011[4] R☉
Luminosity0.021 L☉
Temperature3,345±60[4] K
Metallicity [Fe/H]−0.30±0.08[4] dex
Rotational velocity (v sin i)< 2.5[6] km/s
Age2.4[4] Gyr
Orbit[7]
CompanionStruve 2398 B
Period (P)294.7 yr
Semi-major axis (a)10.50″
Eccentricity (e)0.70
Inclination (i)52.5°
Longitude of the node (Ω)139.9°
Periastron epoch (T)1778.0
Argument of periastron (ω)
(secondary)		203.8°
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, G 227-047
Database references
SIMBADThe system
A
B

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,[8] and their active surfaces are sources of X-ray emission.[9] They are orbiting with period of about 295 years, at a separation of about 56 astronomical units[10] with an orbital eccentricity (ovalness) of 0.70.[7]

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.[11]

Planetary system

In 2016, a planet candidate on a 2.7-day orbit was proposed around Struve 2398 B, although the signal was found to be comparable with an instrumental noise floor.[12] In 2019, two candidate planets were detected in orbit around component B using the radial velocity method, without detection of the previous candidate.[13]

The Struve 2398 B (Gliese 725 B) planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) ≥15.7±5.7 M⊕ 0.261+0.022
−0.028		 91.29+0.31
−0.24		 0.06+0.26
−0.06		 — —
c (unconfirmed) ≥13.1+8.1
−6.4 M⊕		 0.428+0.037
−0.045		 192.4+2.2
−1.9		 0.03+0.22
−0.03		 — —

See also

References

  1. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ↑ Rojas-Ayala, Bárbara; et al. (April 2012). "Metallicity and Temperature Indicators in M Dwarf K-band Spectra: Testing New and Updated Calibrations with Observations of 133 Solar Neighborhood M Dwarfs". The Astrophysical Journal. 748 (2): 93. arXiv:1112.4567. Bibcode:2012ApJ...748...93R. doi:10.1088/0004-637X/748/2/93. S2CID 41902340. See Table 3.
  3. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  4. 1 2 3 4 5 6 7 8 Mann, Andrew W.; et al. (May 2015), "How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius", The Astrophysical Journal, 804 (1): 38, arXiv:1501.01635, Bibcode:2015ApJ...804...64M, doi:10.1088/0004-637X/804/1/64, S2CID 19269312, 64.
  5. 1 2 3 4 Pineda, J. Sebastian; Youngblood, Allison; France, Kevin (September 2021). "The M-dwarf Ultraviolet Spectroscopic Sample. I. Determining Stellar Parameters for Field Stars". The Astrophysical Journal. 918 (1): 23. arXiv:2106.07656. Bibcode:2021ApJ...918...40P. doi:10.3847/1538-4357/ac0aea. S2CID 235435757. 40.
  6. 1 2 Reiners, Ansgar; et al. (April 2012), "A Catalog of Rotation and Activity in Early-M Stars", The Astronomical Journal, 143 (4): 15, arXiv:1201.5774, Bibcode:2012AJ....143...93R, doi:10.1088/0004-6256/143/4/93, S2CID 118425326, 93.
  7. 1 2 Baize, P. (October 1976). "Orbital elements of eighteen visual double stars". Astronomy and Astrophysics Supplement Series. 26: 177–193. Bibcode:1976A&AS...26..177B. Listed as ADS 11632.
  8. ↑ Pettersen, B. R. (1991), "The nearby flare stars", Società Astronomica Italiana, Memorie, 62: 217–242, Bibcode:1991MmSAI..62..217P.
  9. ↑ Schmitt, J. H. M. M.; Fleming, T. A.; Giampapa, M. S. (September 1995). "The X-ray view of the low-mass stars in the solar neighborhood". The Astrophysical Journal. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
  10. ↑ "Struve 2398 AB". Retrieved 2010-10-22.
  11. ↑ Allen, C.; Herrera, M. A. (1998), "The galactic orbits of nearby UV Ceti stars", Revista Mexicana de Astronomía y Astrofísica, 34: 37–46, Bibcode:1998RMxAA..34...37A.
  12. ↑ Berdiñas, Z. M.; Amado, P. J.; Anglada-Escudé, G.; Rodríguez-López, C.; Barnes, J. (2016), "High-cadence spectroscopy of M dwarfs – I. Analysis of systematic effects in HARPS-N line profile measurements on the bright binary GJ 725A+B", Monthly Notices of the Royal Astronomical Society, 459 (4): 3551–3564, arXiv:1604.05312, doi:10.1093/mnras/stw906
  13. ↑ Barnes, J. R.; et al. (2019-06-11), Frequency of planets orbiting M dwarfs in the Solar neighbourhood, arXiv:1906.04644v1
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