S Trianguli Australis

S Trianguli Australis is a yellow-white hued variable star in the constellation Triangulum Australe. It is a dim star near the lower limit of visibility with the naked eye, having a typical apparent visual magnitude of 6.41.[2] Based upon an annual parallax shift of 1.08 mas,[1] it is located 3,030 light years from the Earth.

S Trianguli Australis
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum Australe
Right ascension  16h 01m 10.71590s[1]
Declination −63° 46′ 35.5324″[1]
Apparent magnitude (V) 6.41[2] (5.95 – 6.81)[3]
Characteristics
Spectral type F8 II[4]
B−V color index 0.567±0.020[5]
Variable type δ Cep[6]
Astrometry
Radial velocity (Rv)2.2±1.3[7] km/s
Proper motion (μ) RA: −2.244[1] mas/yr
Dec.: −2.804[1] mas/yr
Parallax (π)1.0753 ± 0.0301[1] mas
Distance3,030 ± 80 ly
(930 ± 30 pc)
Absolute magnitude (MV)−3.53[8]
Details
Mass2.8[9] M☉
Radius39.2[9] R☉
Surface gravity (log g)2.1±0.1[2] cgs
Temperature5,976±67[2] K
Metallicity [Fe/H]0.12±0.05[2] dex
Other designations
S TrA, CD−63° 1146, HD 142941, HIP 78476, HR 5939, SAO 253377[10]
Database references
SIMBADdata

A Classical Cepheid variable, its apparent magnitude ranges from 5.95 to 6.81 over 6.32344 days.[3] It is a bright giant with a nominal stellar classification of F8 II,[4] that pulsates between spectral types F6II-G2.[3] The star has 2.8 times the mass of the Sun and 39.2 times the Sun's radius.[9] It is losing mass at the estimated rate of 2.8×10−10 M☉·yr−1.[8]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. Soubiran, Caroline; et al. (2016). "The PASTEL catalogue: 2016 version". Astronomy & Astrophysics. 591 (118): A118. arXiv:1605.07384. Bibcode:2016A&A...591A.118S. doi:10.1051/0004-6361/201628497.
  3. Watson, Christopher (4 January 2010). "S Trianguli Australis". AAVSO Website. American Association of Variable Star Observers. Retrieved 23 May 2015.
  4. Houk, Nancy; Cowley, A. P. (1979). "Michigan catalogue of two-dimensional spectral types for the HD stars". Ann Arbor : Dept. Of Astronomy. Ann Arbor, Michigan. 1. Bibcode:1978mcts.book.....H.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  7. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  8. Neilson, Hilding R.; Lester, John B. (September 2008), "On the Enhancement of Mass Loss in Cepheids Due to Radial Pulsation", The Astrophysical Journal, 684 (1): 569–587, arXiv:0803.4198, Bibcode:2008ApJ...684..569N, doi:10.1086/588650.
  9. Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V. (2014). "Spectroscopic studies of Cepheids in Circinus (AV Cir, BP Cir) and Triangulum Australe (R TrA, S TrA, U TrA, LR TrA)". Astronomy Letters. 40 (12): 800. Bibcode:2014AstL...40..800U. doi:10.1134/S1063773714110061.
  10. "S TrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 5 September 2018.
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