Tau Persei

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]

τ Persei
Location of τ Persei (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Perseus
Right ascension  02h 45m 15.46108s[1]
Declination +52° 45′ 44.9240″[1]
Apparent magnitude (V) 3.94 - 4.07[2]
Characteristics
U−B color index +0.46[3]
B−V color index +0.74[3]
Variable type Algol[2]
τ Per A
Spectral type G8 IIIa[3]
U−B color index +0.68[3]
B−V color index +0.91[3]
τ Per B
Spectral type A3-4 V[3]
U−B color index +0.07[3]
B−V color index +0.15[3]
Astrometry
Radial velocity (Rv)2.2 ± 0.7[4] km/s
Proper motion (μ) RA: −1.26[1] mas/yr
Dec.: −4.37[1] mas/yr
Parallax (π)12.83 ± 0.36[1] mas
Distance254 ± 7 ly
(78 ± 2 pc)
Absolute magnitude (MV)−0.65[3]
−0.45 / 1.26[3]
Orbit[5]
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
Mass2.99 ± 0.10[6] M☉
Radius16.08 ± 0.54[6] R☉
Luminosity191[6] L☉
Surface gravity (log g)2.47 ± 0.03[6] cgs
Temperature5507 ± 83[6] K
Metallicity [Fe/H]−0.20 ± 0.03[6] dex
Age0.39 ± 0.05[6] Gyr
τ Per B
Mass1.8[3] M☉
Radius2.2[3] R☉
Temperature8970 ± 150[3] K
Other designations
18 Per, BD+52° 641, HD 17878, HD 17879, HIP 13531, HR 854, SAO 23685
Database references
SIMBADdata

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.[7]

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.).[8]

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gollark: I actually have a neat macro which stores all function calls' `()` results in a `Vec` for safekeeping.

References
  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 4 April 2017.
  6. 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.
  7. McAlister, H. A. (1981). "Speckle interferometry of Tau Persei". The Astronomical Journal. 86: 1397. Bibcode:1981AJ.....86.1397M. doi:10.1086/113021.
  8. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
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