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τ Persei
	Location of τ Persei (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Perseus
Right ascension	02h 45m 15.46108s
Declination	+52° 45′ 44.9240″
Apparent magnitude (V)	3.94 - 4.07
Characteristics
U−B color index	+0.46
B−V color index	+0.74
Variable type	Algol
τ Per A
Spectral type	G8 IIIa
U−B color index	+0.68
B−V color index	+0.91
τ Per B
Spectral type	A3-4 V
U−B color index	+0.07
B−V color index	+0.15
Astrometry
Radial velocity (Rv)	2.2 ± 0.7 km/s
Proper motion (μ)	RA: −1.26 mas/yr ; Dec.: −4.37 mas/yr
Parallax (π)	12.83 ± 0.36 mas
Distance	254 ± 7 ly ; (78 ± 2 pc)
Absolute magnitude (MV)	−0.65; −0.45 / 1.26
Orbit
Period (P)	4.149 yr
Semi-major axis (a)	0.055
Eccentricity (e)	0.728
Inclination (i)	94.5°
Longitude of the node (Ω)	100.6°
Periastron epoch (T)	B 2013.888
Argument of periastron (ω); (secondary)	54.1°
Details
τ Per A
Mass	2.99 ± 0.10 M☉
Radius	16.08 ± 0.54 R☉
Luminosity	191 L☉
Surface gravity (log g)	2.47 ± 0.03 cgs
Temperature	5507 ± 83 K
Metallicity [Fe/H]	−0.20 ± 0.03 dex
Age	0.39 ± 0.05 Gyr
τ Per B
Mass	1.8 M☉
Radius	2.2 R☉
Temperature	8970 ± 150 K
Other designations
	18 Per, BD+52°641, HD 17878, HD 17879, HIP 13531, HR 854, SAO 23685
Database references
SIMBAD	data

Tau Persei (τ Per), also known as 18 Persei, is a binary star in the constellation of Perseus. The system is fairly close, and is located about 254 light-years (78 parsecs) away, based on its parallax.^[1]

Light curves for the 1989 eclipse of Tau Persei, plotted from data published by Schmidtke and Hopkins (1990)^[7]

Tau Persei is an eclipsing binary, which means the two stellar components orbit each other in such an orientation that they periodically eclipse each other, while blocking the other's light. Unlike many eclipsing binaries that have short orbital periods, Tau Persei has an orbital period of 4.15 years. With a semi-major axis of 0.055 arcseconds,^[5] this is one of the few eclipsing binaries whose components can be resolved with interferometry.^[8]

The primary component of Tau Persei is a red giant with a spectral type of G8III. It has a radius 16 times that of the Sun, and is about 390 million years old.^[6] Its companion is an A-type main-sequence star. In 1989, the primary star eclipsed the secondary, allowing for the stellar parameters to be derived via its light curve.^[3]

Naming

In Chinese, 大陵 (Dà Líng), meaning Mausoleum, refers to an asterism consisting of τ Persei, 9 Persei, ι Persei, κ Persei, β Persei, ρ Persei, 16 Persei and 12 Persei. Consequently, the Chinese name for τ Persei itself is 大陵二 (Dà Líng èr, English: the Second Star of Mausoleum.).^[9]

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 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. Bibcode:2009yCat....102025S.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Griffin, R. E. M.; Schroder, K. P.; Misch, A.; Griffin, R. F. (1992). "Optical Spectra of Zeta-Aurigae Binary Systems - Part Three - the 1989 Eclipse of Tau-Persei". Astronomy and Astrophysics. 254: 289. Bibcode:1992A&A...254..289G.
^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
^ ^a ^b "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 4 April 2017.
^ ^a ^b ^c ^d ^e ^f ^g ^h Maldonado, J.; Villaver, E.; Eiroa, C. (2013). "The metallicity signature of evolved stars with planets". Astronomy & Astrophysics. 554: 2013. arXiv:1303.3418. Bibcode:2013A&A...554A..84M. doi:10.1051/0004-6361/201321082. S2CID 119289111.
^ Schmidtke, Paul C.; Hopkins, Jeffrey L. (February 1990). "Photometry of the 1989 eclipse of τ Persei". Astrophysics and Space Science. 164 (2): 323–328. Bibcode:1990Ap&SS.164..323S. doi:10.1007/BF00658833. S2CID 121586503. Retrieved 20 July 2022.
^ McAlister, H. A. (1981). "Speckle interferometry of Tau Persei". The Astronomical Journal. 86: 1397. Bibcode:1981AJ.....86.1397M. doi:10.1086/113021.
^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日 Archived 2012-02-04 at the Wayback Machine