Astronomy:Struve 2398

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Short description: Binary star system in the constellation Draco

Coordinates: Sky map 18h 42m 46.67934s, +59° 37′ 49.4724″

Struve 2398
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
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Draco[1][2]
Struve 2398 A
Right ascension  18h 42m 46.70439s[3]
Declination +59° 37′ 49.4095″[3]
Apparent magnitude (V) 8.94[4]
Struve 2398 B
Right ascension  18h 42m 46.89467s[5]
Declination +59° 37′ 36.7212″[5]
Apparent magnitude (V) 9.70[4]
Characteristics
A
Evolutionary stage red dwarf[6]
Spectral type M3 V[7]
U−B color index 1.10[8]
B−V color index 1.54[8]
Variable type Flare star[9]
B
Evolutionary stage red dwarf[6]
Spectral type M3.5 V[7]
U−B color index 1.14[8]
B−V color index 1.59[8]
Astrometry
Struve 2398 A
Radial velocity (Rv)−1.30±0.12[3] km/s
Proper motion (μ) RA: –1311.679[3] mas/yr
Dec.: +1792.325[3] mas/yr
Parallax (π)283.8401 ± 0.0220[3] mas
Distance11.4908 ± 0.0009 ly
(3.5231 ± 0.0003 pc)
Absolute magnitude (MV)+11.18[1]
Struve 2398 B
Radial velocity (Rv)0.88±0.15[5] km/s
Proper motion (μ) RA: –1400.264 mas/yr
Dec.: +1862.525 mas/yr
Parallax (π)283.8378 ± 0.0287[5] mas
Distance11.491 ± 0.001 ly
(3.5231 ± 0.0004 pc)
Absolute magnitude (MV)+12.01[2]
Orbit[10]
Period (P)1,166±60 years
Semi-major axis (a)63±1 astronomical unit|AU[11]
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
Mass0.330±0.008[11] M☉
Radius0.351±0.003[11] R☉
Luminosity0.01552±0.00007[11] L☉
Surface gravity (log g)4.87±0.01[11] cgs
Temperature3,433±68[11] K
Metallicity [Fe/H]−0.23±0.08[7] dex
Rotation103.1±6.1[12] days
Rotational velocity (v sin i)< 2.5[13] km/s
Age6.2±2.3[11] Gyr
Struve 2398 B
Mass0.25±0.02[14] M☉
Radius0.280±0.005[14] R☉
Luminosity0.00916±0.00006[14] L☉
Surface gravity (log g)4.82±0.06[14] cgs
Temperature3,379±31[14] K
Metallicity [Fe/H]−0.30±0.08[7] dex
Rotation105.1±3.3[14] days
Rotational velocity (v sin i)< 2.5[13] km/s
Age8.7±2.1[14] Gyr
Other designations
Σ 2398, BD+59°1915, GJ 725, ADS 11632
Struve 2398 A: Vyssotsky 184, NSV 11288, HD 173739, HIP 91768, G 227-046, LHS 58
Struve 2398 B: HD 173740, HIP 91772, G 227-047, LHS 59
Database references
SIMBADThe system
A
B
Exoplanet Archivedata

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 are each sources of X-ray emission.[15] 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.[11]

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.[16]

Planetary systems

Both stars of the Struve 2398 system are known to host planets.

Struve 2398 A has one known planet, a likely super-Earth discovered in 2024 using the radial velocity method. This planet has a minimum mass 2.8 times that of Earth, and has a close orbit with a period of 11 days; it is too close to its star to be in the habitable zone. TESS observations show that the planet likely does not transit its host star.[11]

Struve 2398 B also hosts one known planet, a super-Earth orbiting within the habitable zone, circling its host star every 37.9 days. An additional planet with an orbital period of 4.765 days is suspected. Both were detected using the radial velocity method and announced in 2025.[14] Other planetary candidates had previously been proposed around star B, but were not confirmed.[17]

The Struve 2398 A (Gliese 725 A) planetary system[11]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b ≥2.78±0.35 M⊕ 0.068±0.001 11.2201±0.0051 — — —
The Struve 2398 B (Gliese 725 B) planetary system[14]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b (unconfirmed) ≥1.5±0.4 M⊕ 0.035±0.001 4.765±0.004 — — —
c ≥3.4±0.7 M⊕ 0.139±0.004 37.90±0.17 — — —

See also

Other systems with multiple planet-hosting stars:

References

  1. ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 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. doi:10.1088/0004-637X/748/2/93. Bibcode: 2012ApJ...748...93R.  See Table 3.
  5. ↑ 5.0 5.1 5.2 5.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  6. ↑ 6.0 6.1 Cortés-Contreras, M.; Caballero, J. A.; Montes, D.; Cardona-Guillén, C.; Béjar, V. J. S.; Cifuentes, C.; Tabernero, H. M.; Zapatero Osorio, M. R. et al. (2024). "CARMENES input catalogue of M dwarfs VIII. Kinematics in the solar neighbourhood". Astronomy and Astrophysics 692. doi:10.1051/0004-6361/202451585. Bibcode: 2024A&A...692A.206C. 
  7. ↑ 7.0 7.1 7.2 7.3 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. doi:10.1088/0004-637X/804/1/64. 64. Bibcode: 2015ApJ...804...64M. 
  8. ↑ 8.0 8.1 8.2 8.3 Myers, J. R.; Sande, C. B.; Miller, A. C.; Warren, W. H.; Tracewell, D. A. (2015). "VizieR Online Data Catalog: SKY2000 Master Catalog, Version 5 (Myers+ 2006)". Vizier Online Data Catalog. Bibcode: 2015yCat.5145....0M. 
  9. ↑ Pettersen, B. R.; Griffin, R. F. (1980). "Non-emission-line flare stars". The Observatory 100: 198. Bibcode: 1980Obs...100..198P. 
  10. ↑ Izmailov, Igor; Khovritchev, Maxim (January 2025). "New Orbital Parameters of 850 Wide Visual Binary Stars and Their Statistical Properties" (in en). Research in Astronomy and Astrophysics 25 (1): 015016. doi:10.1088/1674-4527/ad9da3. ISSN 1674-4527. Bibcode: 2025RAA....25a5016I. 
  11. ↑ 11.00 11.01 11.02 11.03 11.04 11.05 11.06 11.07 11.08 11.09 Cortés-Zuleta, P.; Boisse, I.; Ould-Elhkim, M.; Wilson, T. G.; Larue, P.; Carmona, A.; Delfosse, X.; Donati, J.-F. et al. (2025-01-01). "GI 725A b: A potential super-Earth detected with SOPHIE and SPIRou in an M dwarf binary system at 3.5 pc" (in en). Astronomy & Astrophysics 693: A164. doi:10.1051/0004-6361/202451646. ISSN 0004-6361. Bibcode: 2025A&A...693A.164C. 
  12. ↑ Donati, J.-F. et al. (October 2023). "Magnetic fields and rotation periods of M dwarfs from SPIRou spectra". Monthly Notices of the Royal Astronomical Society 525 (2): 2015–2039. doi:10.1093/mnras/stad2301. Bibcode: 2023MNRAS.525.2015D. 
  13. ↑ 13.0 13.1 Reiners, Ansgar et al. (April 2012). "A Catalog of Rotation and Activity in Early-M Stars". The Astronomical Journal 143 (4): 15. doi:10.1088/0004-6256/143/4/93. 93. Bibcode: 2012AJ....143...93R. 
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 Ould-Elhkim, M.; Moutou, C.; Donati, J.-F. et al. (2026). "The SPIRou Legacy Survey. Detection of a nearby world orbiting in the habitable zone of Gl 725 B achieved by correcting strong telluric contamination in near-infrared radial velocities with wapiti". Astronomy & Astrophysics (EDP Sciences) 705: A234. doi:10.1051/0004-6361/202555469. ISSN 0004-6361. 
  15. ↑ 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. doi:10.1086/176149. Bibcode: 1995ApJ...450..392S. 
  16. ↑ 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. 
  17. ↑ 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. doi:10.1093/mnras/stw906. Bibcode: 2016MNRAS.459.3551B. 



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