ADS 7251

ADS 7251 is a binary star system 6.33 parsecs (20.66 light years) from the Sun. The components are near-identical red dwarfs separated by 17″ in 2019.

ADS 7251

Observation data Epoch J2000      Equinox J2000
Constellation	Ursa Major
ADS 7251 A
Right ascension	09^h 14^m 22.7749^s[1]
Declination	52° 41′ 11.792″[1]
Apparent magnitude (V)	7.64[2]
ADS 7251 B
Right ascension	09^h 14^m 24.6828^s[3]
Declination	52^h 41^m 10.902^s[3]
Apparent magnitude (V)	7.70[2]
Characteristics
ADS 7251 A (HD 79210)
Spectral type	M0V[4]
Apparent magnitude (B)	9.05[2]
Apparent magnitude (G)	6.976[1]
Apparent magnitude (J)	4.89[lower-alpha 1][5]
Apparent magnitude (H)	3.987[lower-alpha 1][5]
Apparent magnitude (K)	3.99[lower-alpha 1][5]
B−V color index	+1.41[6]
J−H color index	+0.90[lower-alpha 2]
J−K color index	+0.90[lower-alpha 2]
ADS 7251 B (HD 79211)
Spectral type	K7V[4]
Apparent magnitude (B)	9.04[2]
Apparent magnitude (G)	7.045[3]
Apparent magnitude (J)	4.779[lower-alpha 1][5]
Apparent magnitude (H)	4.043[lower-alpha 1][5]
Apparent magnitude (K)	4.14[lower-alpha 1][5]
B−V color index	+1.42[6]
J−H color index	+0.74[lower-alpha 2]
J−K color index	+0.64[lower-alpha 2]
Astrometry
ADS 7251 A (HD 79210)
Radial velocity (Rv)	11.245±0.0007[1] km/s
Proper motion (μ)	RA: −1,545.787±0.018[1] mas/yr Dec.: −569.053±0.018[1] mas/yr
Parallax (π)	157.8879 ± 0.0197[1] mas
Distance	20.657 ± 0.003 ly (6.3336 ± 0.0008 pc)
Absolute magnitude (MV)	8.637[7]
ADS 7251 B
Radial velocity (Rv)	12.104±0.0008[3] km/s
Proper motion (μ)	RA: −1,573.040±0.018[3] mas/yr Dec.: −659.906±0.018[3] mas/yr
Parallax (π)	157.8825 ± 0.0211[3] mas
Distance	20.658 ± 0.003 ly (6.3338 ± 0.0008 pc)
Absolute magnitude (MV)	8.712[7]
Orbit[8]
Period (P)	975 years yr
Semi-major axis (a)	16.725″
Eccentricity (e)	0.28
Details[9]
A
Mass	0.69±0.07 M☉
Radius	0.58±0.02 R☉
Luminosity	1.20±0.01 L☉
Surface gravity (log g)	4.68±0.07 cgs
Temperature	4,024±51 K
Rotation	16.3+3.5 −1.3
Rotational velocity (v sin i)	2.0±1.2 km/s
B
Mass	0.64±0.07 M☉
Radius	0.58±0.03 R☉
Luminosity	1.20±0.01 L☉
Surface gravity (log g)	4.68±0.07 cgs
Temperature	4,005±51 K
Rotation	16.61±0.04
Rotational velocity (v sin i)	2.3±1.5 km/s
Age	1–7 Gyr
Other designations
GJ 388, ADS 7251, WDS J09144+5241
A: BD+53°1320, HD 79210, HIP 45343
B: BD+53°1321, HD 79211, HIP 120005
Database references
SIMBAD	The system
	A
	B

The two stars share a mildly eccentric orbit with a semimajor axis of 16.725″ and a period of 975 years. Their separation has closed from 21.1″ when they were discovered by F. G. W. Struve in 1821 to 16.9″ in 2019. Struve also documented two much fainter stars about 3′ from the two red dwarfs.[10]

ADS 7251 A is 0.06 magnitudes (six percent) brighter than ADS 7251 B. A catalogue of MK spectral classes lists both stars as secondary standards, with ADS 7251 A being class M0V and ADS 7251 B being class K7V, noted as being unusual in the brighter star having a later spectral type.[4] Other publications have described the stars as being both K7V, both M0V, or the primary being K7V and the secondary M0V.[11][9]

Planetary system

ADS 7251 B also known as Gliese 338B or HD 79211, is orbited by one known super-Earth planet detected by radial velocity.[9]

The ADS 7251 B (Gliese 338 B) planetary system

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	9.97+1.47 −1.38 M⊕	0.141±0.005	24.45±0.02	0.11+0.11 −0.08	—	—

Notes

1. 2MASS infrared magnitudes flagged as unreliable or upper limits
2. Calculated from 2MASS magnitudes

References

1. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
2. Huang, Y.; Liu, X. -W.; Yuan, H. -B.; Xiang, M. -S.; Chen, B. -Q.; Zhang, H. -W. (2015). "Empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs and giants based on interferometric data". Monthly Notices of the Royal Astronomical Society. 454 (3): 2863. arXiv:1508.06080. Bibcode:2015MNRAS.454.2863H. doi:10.1093/mnras/stv1991. S2CID 118487917.
3. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
4. Kirkpatrick, J. D.; et al. (1991). "A standard stellar spectral sequence in the red/near-infrared - Classes K5 to M9". Astrophysical Journal Supplement Series. 77: 417. Bibcode:1991ApJS...77..417K. doi:10.1086/191611.
5. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: 2003yCat.2246....0C. 2246. Bibcode:2003yCat.2246....0C.
6. Bobylev, V. V.; Goncharov, G. A.; Bajkova, A. T. (2007). "VizieR Online Data Catalog: Orion Spiral Arm CAtalogue (OSACA) (Bobylev+, 2006)". Vizier Online Data Catalog. Bibcode:2007yCat..90830821B.
7. Houdebine, Éric R.; Mullan, D. J.; Doyle, J. G.; de la Vieuville, Geoffroy; Butler, C. J.; Paletou, F. (2019). "The Mass-Activity Relationships in M and K Dwarfs. I. Stellar Parameters of Our Sample of M and K Dwarfs". The Astronomical Journal. 158 (2): 56. arXiv:1905.07921. Bibcode:2019AJ....158...56H. doi:10.3847/1538-3881/ab23fe. S2CID 159041104.
8. Malkov, O. Yu.; et al. (2012). "Dynamical Masses of a Selected Sample of Orbital Binaries". Astronomy & Astrophysics. 546: 5. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. A69.
9. González-Álvarez, E.; Osorio, M. R. Zapatero; Caballero, J. A.; Sanz-Forcada, J.; Béjar, V. J. S.; González-Cuesta, L.; Dreizler, S.; Bauer, F. F.; Rodríguez, E.; Tal-Or, L.; Zechmeister, M. (May 2020). "The CARMENES search for exoplanets around M dwarfs. A super-Earth planet orbiting HD 79211 (GJ 338 B)". Astronomy & Astrophysics. 637: A93. arXiv:2003.13052. Bibcode:2020A&A...637A..93G. doi:10.1051/0004-6361/201937050. ISSN 0004-6361.
10. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
11. Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog: B/Mk. Originally Published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S.