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40 Aurigae
Observation data; Epoch J2000 Equinox J2000
Constellation	Auriga
Right ascension	06h 06m 35.09702s
Declination	+38° 28′ 57.5204″
Apparent magnitude (V)	5.345
Characteristics
Spectral type	A4m
U−B color index	+0.11
B−V color index	+0.23
Astrometry
Radial velocity (Rv)	16.90 ± 7.4 km/s
Proper motion (μ)	RA: 9.84 mas/yr ; Dec.: −52.54 mas/yr
Parallax (π)	9.57 ± 0.34 mas
Distance	340 ± 10 ly ; (104 ± 4 pc)
Orbit
Primary	40 Aur A
Companion	40 Aur B
Period (P)	28.28 d
Eccentricity (e)	0.56
Periastron epoch (T)	JD 2420468.197
Argument of periastron (ω); (secondary)	178.4°
Semi-amplitude (K1); (primary)	51.4 km/s
Semi-amplitude (K2); (secondary)	62.5 km/s
Details
Surface gravity (log g)	3.88 ± 0.08 cgs
Temperature	7838 ± 52 K
Metallicity [Fe/H]	+0.35 ± 0.05 dex
Other designations
	HD 41357, GCRV 3828, IRAS 06031+3829, SBC7 265, 2MASS J06063509+3828578, AG+38° 663, GSC 02925-00806, PLX 1403, TD1 5967, BD+38° 1377, HIC 28946, PPM Star Catalogue 71223, TYC 2925-806-1, FK5 2465, HIP 28946, ROT 972, UBV 6148, GC 7723, HR 2143, SAO 58749, uvby98 100041357.
Database references
SIMBAD	data

40 Aurigae is a binary star in the constellation Auriga. Its apparent magnitude is 5.345,^[2] meaning it can just barely be seen with the naked eye. Based on parallax estimates made by the Hipparcos spacecraft, the system is located some 340 light-years (104 parsecs) away.^[1]

40 Aurigae is a spectroscopic binary, meaning the two stars are too close to be individually resolved, but periodic Doppler shifts in their spectra indicate there must be orbital motion. In this case, light from both stars can be detected and it is a double-lined spectroscopic binary.^[3] The two have an orbital period of 28.28 days and a fairly high eccentricity of 0.56.^[3] The primary star is an A-type main-sequence star and shows unusual absorption lines in its spectrum, so it is an Am star^[3] with an effective temperature of 7,838 K.^[6]

References

^ ^a ^b ^c ^d ^e ^f van Leeuwen, F.; et al. (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.
^ ^a ^b Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H.
^ ^a ^b ^c ^d ^e Pourbaix, D.; et al. (2004). "S_B⁹: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727–732. arXiv:astro-ph/0406573. Bibcode:2004A&A...424..727P. doi:10.1051/0004-6361:20041213. S2CID 119387088.
^ ^a ^b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
^ Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
^ ^a ^b Koleva, M.; Vazdekis, A. (2012). "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library". Astronomy & Astrophysics. 538: A143. arXiv:1111.5449. Bibcode:2012A&A...538A.143K. doi:10.1051/0004-6361/201118065. S2CID 53999614.