R Trianguli Australis

R Trianguli Australis is a yellow-white hued variable star in the southern constellation Triangulum Australe. It is near the limit of visibility to the naked eye, having a typical apparent visual magnitude of 6.73.[2] Based upon an annual parallax shift of 1.48 mas,[1] it is located 2,210 light years away. R TrA is moving closer with a heliocentric radial velocity of −13 km/s.[6]

R Trianguli Australis
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum Australe
Right ascension 15h 19m 45.71231s[1]
Declination −66° 29′ 45.7417″[1]
Apparent magnitude (V) 6.73[2] (6.33 - 6.90)[3]
Characteristics
Spectral type F7 Ib/II[4]
Variable type δ Cep[5]
Astrometry
Radial velocity (Rv)−13.2±1.6[6] km/s
Proper motion (μ) RA: −5.113[1] mas/yr
Dec.: −8.317[1] mas/yr
Parallax (π)1.4754 ± 0.0371[1] mas
Distance2,210 ± 60 ly
(680 ± 20 pc)
Absolute magnitude (MV)2.69[7]
Details
Mass5.42 or 5.66[8] M☉
Radius24.7±1.9[9] or 35.8±0.8[8] R☉
Surface gravity (log g)2.10[8] cgs
Temperature5,852±21[8] K
Metallicity [Fe/H]+0.06±0.08[7] dex
Rotational velocity (v sin i)16 km/s
Other designations
R TrA, CD−66° 1728, HD 135592, HIP 75018, SAO 253107[10]
Database references
SIMBADdata

This is a Classical Cepheid variable with an apparent magnitude that ranges from 6.33 to 6.90 over 3.38926 days.[3] It is a bright giant/supergiant with a nominal stellar classification of F7 Ib/II,[4] but pulsates between spectral types F5Ib/II-G5.[3] Depending on the method employed, the estimated mass is 5.42 or 5.66 times the mass of the Sun and it has 24.7 or 35.8 times the Sun's radius.[8] R TrA has an infrared excess that is being emitted by circumstellar silicate dust heated to 150–200 K. It is losing mass at the rate of 4×10−9 M☉·y−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. 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, S2CID 119257644.
  3. Watson, Christopher (4 January 2010). "R 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. 1. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. Bibcode:1978mcts.book.....H.
  5. 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, S2CID 125853869.
  6. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 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.
  7. Luck, R. E.; et al. (August 2011). "The Distribution of the Elements in the Galactic Disk. II. Azimuthal and Radial Variation in Abundances from Cepheids". The Astronomical Journal. 142 (2): 12. arXiv:1106.0182. Bibcode:2011AJ....142...51L. doi:10.1088/0004-6256/142/2/51. S2CID 119288363. 51.
  8. 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. S2CID 122745580.
  9. Moskalik, P.; Gorynya, N. A. (2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica. 55: 247. arXiv:astro-ph/0507076. Bibcode:2005AcA....55..247M.
  10. "R TrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 5 September 2018.
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