Chi Draconis

Chi Draconis (χ Dra, χ Draconis, Chi Draconis) is a magnitude 3.6 binary star in the constellation Draco. It also has the Flamsteed designation 44 Draconis. At a distance of 27 light years, it is one of the forty or so closest stars.

χ Draconis

Location of χ Draconis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Draco
Right ascension	18h 21m 03.38255s[1]
Declination	+72° 43′ 58.2518″[1]
Apparent magnitude (V)	3.570[2]
Characteristics
Spectral type	F7V / K0V[3]
U−B color index	−0.06[4]
B−V color index	+0.49[4]
Variable type	Suspected[5]
Astrometry
Radial velocity (Rv)	+32.4[2] km/s
Proper motion (μ)	RA: +531.21[1] mas/yr Dec.: −349.71[1] mas/yr
Parallax (π)	120.05 ± 0.15 mas[3]
Distance	27.17 ± 0.03 ly (8.33 ± 0.01 pc)
Absolute magnitude (MV)	4.04[2]
Orbit[6]
Primary	χ Dra Aa
Companion	χ Dra Ab
Period (P)	0.7680599±0.000061 yr
Semi-major axis (a)	0.1244±0.0011″
Eccentricity (e)	0.428±0.012
Inclination (i)	74.42±0.58°
Longitude of the node (Ω)	230.30±0.51°
Periastron epoch (T)	1,984.8324±0.0026
Argument of periastron (ω) (secondary)	119.3±1.1°
Details
χ Dra Aa
Mass	1.029±0.026[3] M☉
Radius	1.20±0.09[3] R☉
Luminosity	1.86[3] L☉
Temperature	6,150±150[3] K
Metallicity [Fe/H]	−0.41[2] dex
Rotational velocity (v sin i)	11[7] km/s
Age	5.3[2] Gyr
χ Dra Ab
Mass	0.748±0.017[3] M☉
Radius	0.73±0.11[3] R☉
Luminosity	0.29[3] L☉
Temperature	4,940±200[3] K
Other designations
χ Dra, 44 Dra, BD+72°839, FK5 695, Gl 713, HD 170153, HIP 89937, HR 6927, LHS 3379, LTT 15438, SAO 9087, NSV 10749[8]
Database references
SIMBAD	data

Binary system

χ Draconis in optical light

χ Draconis is a spectroscopic binary which has been resolved using speckle interferometry.^[4] The primary is an F7 main sequence star. The spectral type of the companion cannot be determined directly with any accuracy, but is known to be between G8 and K2 and is assumed to be K0. The properties of the secondary suggest that it is also a main-sequence star. The separation of the two stars varies between about 0.05″ and 0.2″ during the eccentric 182-day orbit.^[9]

The primary star has a mass fractionally higher than the Sun's, but is significantly larger and hotter resulting in it being 86% more luminous.^[3] Its age is estimated to be about five billion years.^[2]

The secondary only has about three-quarters the mass of the Sun and is both cooler and smaller. It is only about 29% as luminous.^[3] It is calculated to be 2.13 magnitudes fainter than the primary, so it would be of sixth magnitude if visible alone.^[10]

Visual companions

Multiple star catalogues list faint widely-separated visible companion stars: a 12th-magnitude star and a 14th-magnitude star about 3′ from χ Draconis, but only about 10″ from each-other.^[11] Both have much smaller parallaxes than χ Draconis and are likely to be unrelated background objects.^[12]

See also

• List of star systems within 25–30 light-years

References

1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
2. Nordström, B.; et al. (May 2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418: 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID 11027621.
3. Torres, G.; Andersen, J.; Giménez, A. (2010). "Accurate masses and radii of normal stars: modern results and applications". The Astronomy and Astrophysics Review. 18 (1–2): 67–126. arXiv:0908.2624. Bibcode:2010A&ARv..18...67T. doi:10.1007/s00159-009-0025-1. S2CID 14006009. See p. 56, entry #15.
4. Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode:1991bsc..book.....H.
5. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
6. Farrington, C. D.; et al. (June 2010). "Separated Fringe Packet Observations with the CHARA Array. I. Methods and New Orbits for χ Draconis, HD 184467, and HD 198084". The Astronomical Journal. 139 (6): 2308–2318. Bibcode:2010AJ....139.2308F. doi:10.1088/0004-6256/139/6/2308.
7. Monin, D. N.; Fabrika, S. N.; Valyavin, G. G. (2002). "Magnetic survey of bright northern main sequence stars". Astronomy & Astrophysics. 396 (1): 131–141. Bibcode:2002A&A...396..131M. doi:10.1051/0004-6361:20021425.
8. "chi Dra -- Star in double system". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2011-10-15.
9. Tomkin, Jocelyn; McAlister, Harold A.; Hartkopf, William I.; Fekel, Francis C. (1987). "The Orbit of the Speckle and Double-Lined Spectroscopic Binary Chi Draconis". The Astronomical Journal. 93: 1236. Bibcode:1987AJ.....93.1236T. doi:10.1086/114404.
10. Hutter, D. J.; Zavala, R. T.; Tycner, C.; Benson, J. A.; Hummel, C. A.; Sanborn, J.; Franz, O. G.; Johnston, K. J. (9 November 2016). "Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity Among Stars of Spectral Types F-K". The Astrophysical Journal Supplement Series. 227 (1): 4. arXiv:1609.05254. Bibcode:2016ApJS..227....4H. doi:10.3847/0067-0049/227/1/4. S2CID 118803592.
11. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 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. ISSN 0004-6256.
12. 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.

External links

• ARICNS
• Chi Draconis 2 at SolStation.
• nStars database entry