Contents

GJ 1245

Triple star system in the constellation Cygnus

V1581 Cygni

Ablue band light curve for a flare of V1581 Cygni. The left-most point shows a 1 sigma error bar. Adapted from Cristaldi and Rodonò (1976)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
GJ 1245 AC
Right ascension	19h53m 55.142s[2]
Declination	+44° 24′ 44.39″[2]
Apparent magnitude (V)	13.46 / 16.75[3]
GJ 1245 B
Right ascension	19h53m 55.141s[4]
Declination	+44° 24′ 54.15″[4]
Apparent magnitude (V)	14.01[3]
Characteristics
Spectral type	M6V / M8V[5] / M6V[6]
Variable type	UV Cet[7]
Astrometry
Radial velocity (Rv)	3.93±0.38[4] km/s
Proper motion (μ)	RA: 349.363(56) mas/yr[4] Dec.: −480.322(54) mas/yr[4]
Parallax (π)	214.5745 ± 0.0476 mas[4]
Distance	15.200 ± 0.003 ly (4.660 ± 0.001 pc)
Absolute magnitude (MV)	15.12 / 18.41[5] / 15.72[3]
Orbit[8]
Primary	GJ 1245 A
Companion	GJ 1245 C
Period (P)	6147±17 d
Semi-major axis (a)	0.8267±0.0008″
Eccentricity (e)	0.334±0.002
Inclination (i)	135.7±0.1°
Longitude of the node (Ω)	261.2±0.2°
Periastron epoch (T)	51506.8±2.1
Argument of periastron (ω) (secondary)	36.1±0.2°
Details
GJ 1245 A
Mass	0.120±0.001[5] M☉
Radius	0.146±0.007[5] R☉
Luminosity	0.0014[5] L☉
Temperature	2,927[5] K
Metallicity [Fe/H]	-0.07[5] dex
Age	~300[citation needed] Myr
GJ 1245 C
Mass	0.081±0.001[5] M☉
Radius	0.087±0.004[5] R☉
Luminosity	0.0003[5] L☉
Temperature	2,611[5] K
Metallicity [Fe/H]	-0.08[5] dex
Other designations
V1581 Cyg, GJ 1245, WDS J19539+4425
GJ 1245 AC: G 208-44, LHS 3494, NLTT 48414, KIC 8451868, 2MASS J19535443+4424541[9]
GJ 1245 B: G 208-45, LHS 3495, NLTT 48415, KIC 8451881, 2MASS J19535508+4424550[6]
Database references
SIMBAD	The system
	A
	C
	B
GJ 1245 Location of GJ 1245 in the constellation Cygnus

GJ 1245 (Gliese 1245) is a double star with components G 208-44 and G 208-45, located 15.2 light-years (4.7 parsecs) away in the constellation Cygnus. G 208-44 is itself a closer double star made up of two red dwarfs, while G 208-45 is also a red dwarf. GJ 1245 is the 43rd closest stellar system to the Solar System.^[10] GJ 1245 A and B are active flare stars,^[11] and the pair are collectively designated V1581 Cygni.^[12]

The largest of the three stars, GJ 1245 A (G 208-44 A) is only 12% the Sun's mass.^[5] Of the other two stars, GJ 1245 C (G 208-44 B), is closest to star A at 2 AU away;^[13] it is 8% of the Sun's mass.^[5] The third star, GJ 1245 B (G 208-45), is 27 AU away from star A,^[13] and is 10% of the Sun's mass; it would appear as bright as Venus does from Earth when viewed from star A.^{[citation needed]}

• List of nearest stars

• Harrington, R. S.; Dahn, C. C.; Kallarakal, V. V.; Guetter, H. H.; Riepe, B. Y.; Walker, R. L.; Pier, J. R.; Vrba, F. J.; Luginbuhl, C. B.; Harris, H. C.; Ables, H. D. (1993). "U.S. Naval Observatory photographic parallaxes - List IX". Astronomical Journal. 105 (4): 1571–1580. Bibcode:1993AJ....105.1571H. doi:10.1086/116537.
• Henry, Todd J.; Subasavage, John P.; Brown, Misty A.; Beaulieu, Thomas D.; Jao, Wei-Chun; Hambly, Nigel C. (2004). "The Solar Neighborhood. X. New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs". The Astronomical Journal. 128 (5): 2460–2473. arXiv:astro-ph/0408240. Bibcode:2004AJ....128.2460H. doi:10.1086/425052. S2CID 15759789.
• Smart, R. L.; Ioannidis, G.; Jones, H. R. A.; Bucciarelli, B.; Lattanzi, M. G. (2010). "Cool dwarfs stars from the Torino Observatory Parallax Program". Astronomy and Astrophysics. 514: A84. arXiv:1003.1465. Bibcode:2010A&A...514A..84S. doi:10.1051/0004-6361/200913424. S2CID 17961025.
• Dittmann, Jason A.; Irwin, Jonathan M.; Charbonneau, David; Berta-Thompson, Zachory K. (2014). "Trigonometric Parallaxes for 1507 Nearby Mid-to-late M Dwarfs". The Astrophysical Journal. 784 (2): 156. arXiv:1312.3241. Bibcode:2014ApJ...784..156D. doi:10.1088/0004-637X/784/2/156. S2CID 18789867. Table with parallaxes.

• http://jumk.de/astronomie/near-stars/v1581-cygni.shtml
• http://www.answers.com/topic/list-of-nearest-stars?cat=travel
• http://www.richweb.f9.co.uk/astro/nearby_stars.htm

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