TU Andromedae

TU Andromedae (TU And) is a variable star of the Mira type in the constellation Andromeda. It has a spectral type of M5e and a visual magnitude which varies between extremes of 7.6 and 13.5.

TU Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 32m 22.72867s[1]
Declination +26° 01′ 45.9211″[1]
Apparent magnitude (V) 7.5 – 13.5[2]
Characteristics
Spectral type M5e[2]
B−V color index 0.96[3]
Variable type Mira[2]
Astrometry
Proper motion (μ) RA: −7.435±0.069[1] mas/yr
Dec.: −3.136±0.057[1] mas/yr
Parallax (π)0.9435 ± 0.0623[1] mas
Distance3,500 ± 200 ly
(1,060 ± 70 pc)
Details
Mass0.87[4] M☉
Luminosity5,200 - 5,400[5] L☉
Surface gravity (log g)−0.44[4] cgs
Temperature2,639[4] K
Metallicity [Fe/H]0.547[4] dex
Other designations
HD 2890, HIP 2546, 2MASS J00322275+2601459
Database references
SIMBADdata

Like all the stars of this kind, TU And is a cool asymptotic giant branch star, meaning it is fusing hydrogen and helium in concentric shells outside an inert core of carbon and oxygen formed earlier in its life on the horizontal branch. Its period is stable at 316.8 days.[2]

The modelled properties of TU Andromedae at maximum brightness are not in agreement with available models of Mira stars (which work for Mira itself). It is uncertain if the problem is in the measured parameters of the star or in imperfections of the models. It had a mass between 1.15 and 1.4 M☉ when it was on the main sequence but is now less massive.[5]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics (in press). arXiv:2012.01533. doi:10.1051/0004-6361/202039657. S2CID 227254300.
  2. TU And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250 Accessed on line 2009-06-30.
  3. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy & Astrophysics, 355: L27–L30, Bibcode:2000A&A...355L..27H.
  4. 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. (2019), "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18", Astronomy and Astrophysics, 628: A94, arXiv:1904.11302, Bibcode:2019A&A...628A..94A, doi:10.1051/0004-6361/201935765.
  5. Hillen, M.; Verhoelst, T.; Degroote, P.; Acke, B.; van Winckel, H. (2012), "The dynamic atmospheres of Mira stars: comparing the CODEX models to PTI time series of TU Andromedae", Astronomy & Astrophysics, 538: L6, arXiv:1201.5815, Bibcode:2012A&A...538L...6H, doi:10.1051/0004-6361/201118653.
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