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.
  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] |
| Distance | 11.4908 ± 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] |
| Distance | 11.491 ± 0.001 ly (3.5231 ± 0.0004 pc) |
| Orbit[5] | |
| Companion | Struve 2398 B |
| Period (P) | 871±108 yr |
| Semi-major axis (a) | 63±1 AU |
| Eccentricity (e) | 0.29±0.01 |
| Inclination (i) | 69.8±0.4° |
| Longitude of the node (Ω) | 143.0±0.3° |
| Argument of periastron (ω) (secondary) | 272.2+2.9 −3.0° |
| Details | |
| Struve 2398 A | |
| Mass | 0.336±0.007[6] M☉ |
| Radius | 0.354±0.003[6] R☉ |
| Luminosity | 0.01511±0.00019[6] L☉ |
| Temperature | 3,401+18 −17[6] K |
| Metallicity [Fe/H] | −0.23±0.08[4] dex |
| Rotation | 103.1±6.1 d[7] |
| Rotational velocity (v sin i) | < 2.5[8] km/s |
| Age | 3.0[4] Gyr |
| Struve 2398 B | |
| Mass | 0.248±0.025[4] M☉ |
| Radius | 0.273±0.011[4] R☉ |
| Luminosity | 0.021 L☉ |
| Temperature | 3,345±60[4] K |
| Metallicity [Fe/H] | −0.30±0.08[4] dex |
| Rotation | 135±15 d[7] |
| Rotational velocity (v sin i) | < 2.5[8] km/s |
| Age | 2.4[4] Gyr |
| Other designations | |
| 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 | |
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,[9] and their active surfaces are sources of X-ray emission.[10] 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.[5]
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
editStruve 2398 A is known to host one 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.[5]
Struve 2398 B may also host planets. In 2016, an Earth-mass planet candidate on a 2.7-day orbit was proposed around Struve 2398 B based on radial velocity observations, although this could not be confirmed as a periodic signal.[12] A 2019 study also using radial velocity instead proposed two candidate Neptune-mass planets on longer-period orbits.[13]
| 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 | — | — | — |
| 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
editReferences
edit- ^ a b c d e 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.
- ^ 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.
- ^ a b c d e 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.
- ^ a b c d e f g h 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.
- ^ a b c d Cortes-Zuleta, P.; Boisse, I.; et al. (November 2024). "Gl 725A b: a potential super-Earth detected with SOPHIE and SPIRou in an M dwarf binary system at 3.5 pc". Astronomy & Astrophysics. arXiv:2411.09506.
- ^ a b c d 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.
- ^ a b Donati, J.-F.; Lehmann, L. T.; 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. arXiv:2307.14190. Bibcode:2023MNRAS.525.2015D. doi:10.1093/mnras/stad2301.
- ^ a b 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.
- ^ Pettersen, B. R. (1991), "The nearby flare stars", Società Astronomica Italiana, Memorie, 62: 217–242, Bibcode:1991MmSAI..62..217P.
- ^ 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.
- ^ 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.
- ^ 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, Bibcode:2016MNRAS.459.3551B, doi:10.1093/mnras/stw906
- ^ a b Barnes, J. R.; et al. (2019-06-11), Frequency of planets orbiting M dwarfs in the Solar neighbourhood, arXiv:1906.04644v1