X Trianguli Australis

X Trianguli Australis is a star in the southern constellation Triangulum Australe. It is a red-hued carbon star with an average apparent magnitude of +5.89. It is approximately 1173 light years (360 parsecs) from Earth,[7] though this could vary by up to 200 light years.[8] It is a semi-regular variable star with two periods of around 385 and 455 days, and is of spectral type C5.5(Nb).[9] It ranges from magnitudes 5.03 to 6.05.[10] Its designation is from the variable star designation developed by German astronomer Friedrich Wilhelm Argelander.

X Trianguli Australis
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum Australe
Right ascension  15h 14m 19.17448s[1]
Declination −70° 04′ 46.1266″[1]
Apparent magnitude (V) +5.75[2]
Characteristics
Spectral type C5.5[3]
B−V color index 3.271±0.019[2]
Variable type Lb[4]
Astrometry
Radial velocity (Rv)−3.2±1.5[5] km/s
Proper motion (μ) RA: +4.276[1] mas/yr
Dec.: −7.566[1] mas/yr
Parallax (π)3.5388 ± 0.1944[1] mas
Distance920 ± 50 ly
(280 ± 20 pc)
Absolute magnitude (MV)−1.97[2]
Details
Luminosity (bolometric)8,599[6] L☉
Temperature2,860±350[6] K
Other designations
X TrA, CPD−69° 2267, HD 134453, HIP 74582, HR 5644, SAO 253062[7]
Database references
SIMBADdata

It is a cool star, with estimates of its surface temperature ranging from 2200 to 2700 Kelvin.[8] A giant star, its diameter is 400 times that of the sun, and if placed at the center of the Solar System would stretch out to 30% further than Mars' orbit. Its absolute magnitude is −2.0.[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.
  3. Warner, B. (1963). "Spectral classification of some Southern late-type peculiar stars". Monthly Notices of the Royal Astronomical Society. 126: 61. Bibcode:1963MNRAS.126...61W. doi:10.1093/mnras/126.1.61.
  4. 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.
  5. 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.
  6. Rau, G.; et al. (April 2017). "The adventure of carbon stars. Observations and modeling of a set of C-rich AGB stars". Astronomy & Astrophysics. 600: 21. arXiv:1701.04331. Bibcode:2017A&A...600A..92R. doi:10.1051/0004-6361/201629337. A92.
  7. "V* X TrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 18 January 2013.
  8. Kaler, Jim (19 October 2012). "X Trianguli Australis". Stars. University of Illinois. Retrieved 18 January 2013.
  9. Tabur, V.; Bedding, T. R. (2009). "Long-term Photometry and Periods for 261 Nearby Pulsating M Giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–61. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x.
  10. "X TrA". International Variable Star Index. American Association of Variable Star Observers. 11 November 2011. Retrieved 18 January 2013.
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