HD 20104

HD 20104 (HR 967) is a visual binary in the northern circumpolar constellation Camelopardalis. The system has a combined apparent magnitude of 6.41,^[9] making it near naked eye visibility. When resolved in a large telescope, HD 20104 appears to be a pair of 7th magnitude A-type main-sequence stars with a separation of about 0.5″.^[10] Located approximately 550 light years away,^[5] the system is approaching the Sun with a heliocentric radial velocity of −6 km/s.^[4]

HD 20104

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Camelopardalis
A
Right ascension	03h 17m 31.527s[1]
Declination	+65° 39′ 30.11″[1]
Apparent magnitude (V)	7.05±0.01[1]
B
Right ascension	03h 17m 31.593s[1]
Declination	+65° 39′ 30.26″[1]
Apparent magnitude (V)	7.39±0.01[1]
Characteristics
A
Spectral type	A2 V[2]
U−B color index	+0.06[3]
B−V color index	+0.08[3]
B
Spectral type	A4V[2]
Astrometry
Radial velocity (Rv)	−6±2[4] km/s
Proper motion (μ)	RA: −10.54 mas/yr[5] Dec.: +5.84 mas/yr[5]
Parallax (π)	5.92 ± 0.65 mas[5]
Distance	approx. 550 ly (approx. 170 pc)
Absolute magnitude (MV)	+0.3[6]
Orbit[7]
Primary	HD 20104 A
Companion	HD 20104 B
Period (P)	350 yr
Semi-major axis (a)	0.46″
Eccentricity (e)	0.4
Inclination (i)	135°
Longitude of the node (Ω)	58°
Periastron epoch (T)	2055.0
Argument of periastron (ω) (secondary)	100°
Details
A
Mass	2.46[8] M☉
B
Mass	2.27[8] M☉
Other designations
BD+65°338, GC 3893, HD 20104, HIP 15309, HR 967, SAO 12686, ADS 2436, WDS J03175+6540
Database references
SIMBAD	The system
	A
	B

The system's stars have masses twice that of the Sun^[8] and effective temperatures ranging from 8,100 to 8,700 K,^[9][11] typical of stars their type. The primary radiates at 71.3 L_☉^[11] − over luminous for its class − and spins with a projected rotational velocity of 159 km/s.^[12] HD 20104 has an age of 313 million years.^[11]

References

1. Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (March 2002). "The Tycho double star catalogue". Astronomy & Astrophysics. 384 (1): 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822. ISSN 0004-6361.
2. Edwards, T. W. (April 1976). "MK classification for visual binary components". The Astronomical Journal. 81: 245. Bibcode:1976AJ.....81..245E. doi:10.1086/111879. ISSN 0004-6256.
3. Haupt, H. F.; Schroll, A. (1974). "Photoelektrische Photometrie von Shell-Sternen". Astronomy and Astrophysics Supplement Series. 15: 311–319. Bibcode:1974A&AS...15..311H. ISSN 0365-0138.
4. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication: 0. Bibcode:1953GCRV..C......0W.
5. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. ISSN 0004-6361.
6. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
7. Heintz, W. D. (July 1998). "Observations of Double Stars. XVIII". The Astrophysical Journal Supplement Series. 117 (2): 587–598. Bibcode:1998ApJS..117..587H. doi:10.1086/313127.
8. Cvetkovic, Zorica; Ninkovic, S. (2010). "On the component masses of visual binaries". Serbian Astronomical Journal. 180 (180): 71–80. Bibcode:2010SerAJ.180...71C. doi:10.2298/SAJ1080071C.
9. Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevič, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; de Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN 0004-6361.
10. 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.
11. Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. ISSN 0004-6361. S2CID 55586789.
12. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007). "Rotational velocities of A-type stars: III. Velocity distributions". Astronomy & Astrophysics. 463 (2): 671–682. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224. ISSN 0004-6361.