Astronomy:Gamma Trianguli Australis

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Short description: Star in the constellation Triangulum Australe
Gamma Trianguli Australis
Triangulum Australe IAU.svg
Red circle.svg
Location of γ Trianguli Australis (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Triangulum Australe
Right ascension  15h 18m 54.58198s[1]
Declination –68° 40′ 46.3654″[1]
Apparent magnitude (V) +2.87[2]
Characteristics
Spectral type A1 V[3][4]
U−B color index –0.02[5]
B−V color index +0.00[5]
Astrometry
Radial velocity (Rv)–3.0[2] km/s
Proper motion (μ) RA: –66.58[1] mas/yr
Dec.: –32.31[1] mas/yr
Parallax (π)17.74 ± 0.12[1] mas
Distance184 ± 1 ly
(56.4 ± 0.4 pc)
Absolute magnitude (MV)−0.89[6]
Details
Mass1.99[7] M☉
Radius5.86[8] R☉
Luminosity249[9] L☉
Surface gravity (log g)3.39[7] cgs
Temperature9,306±316[7] K
Rotational velocity (v sin i)199[4] km/s
Age260[10] Myr
Other designations
γ TrA, CD−68° 1503, FK5 560, HD 135382, HIP 74946, HR 5671, SAO 253097[11]
Database references
SIMBADdata

Gamma Trianguli Australis, Latinized from γ Trianguli Australis, is a single,[12] white-hued star in the southern constellation of Triangulum Australe. Along with Alpha and Beta Trianguli Australis it forms a prominent triangular asterism that gives the constellation its name (Latin for southern triangle). It is the third-brightest member of this constellation with an apparent visual magnitude of +2.87.[2] Based upon parallax measurements, Gamma Trianguli Australis is located at a distance of about 184 light-years (56 parsecs) from Earth.[1]

The spectrum of this star matches a stellar classification of A1 V,[3][4] which identifies it as an A-type main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. An unusual abundance of the element europium demonstrates it to be a peculiar, or Ap star.[13] Most stars of this type are slow rotators,[14] but Gamma Trianguli Australis displays a very high rate of rotation with a projected rotational velocity of 199 km s−1.[4] It has an estimated age of 260 million years.[10]

This system shows an excess emission of infrared radiation, suggesting that there is a circumstellar disk of dust orbiting this star. The mean temperature of the emission is 50 K, corresponding to a separation from the star of 481 astronomical units.[8]

Modern legacy

γ TrA appears on the flag of Brazil, symbolising the state of Paraná.[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V 
  2. ↑ 2.0 2.1 2.2 Wielen, R. et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg (Astronomisches Rechen-Institut Heidelberg) 35 (35): 1, Bibcode: 1999VeARI..35....1W 
  3. ↑ 3.0 3.1 Levato, O. H. (August 1972), "Rotational Velocities and Spectral Types of Some A-Type Stars", Publications of the Astronomical Society of the Pacific 84 (500): 584, doi:10.1086/129336, Bibcode: 1972PASP...84..584L 
  4. ↑ 4.0 4.1 4.2 4.3 Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, doi:10.1051/0004-6361:20065224, Bibcode: 2007A&A...463..671R 
  5. ↑ 5.0 5.1 Johnson, H. L. et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory 4 (99): 99. Bibcode: 1966CoLPL...4...99J. 
  6. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 7.2 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  8. ↑ 8.0 8.1 Rhee, Joseph H. et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal 660 (2): 1556–1571, doi:10.1086/509912, Bibcode: 2007ApJ...660.1556R 
  9. ↑ Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics 537: A120, doi:10.1051/0004-6361/201117691, Bibcode: 2012A&A...537A.120Z. 
  10. ↑ 10.0 10.1 Rieke, G. H. et al. (February 2005), "Decay of Planetary Debris Disks", The Astrophysical Journal 620 (2): 1010–1026, doi:10.1086/426937, Bibcode: 2005ApJ...620.1010R 
  11. ↑ "gam TrA -- Variable Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Gamma+Trianguli+Australis, retrieved 2012-02-04 
  12. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  13. ↑ Sokolov, N. A. (June 1998), "Effective temperatures of AP stars", Astronomy and Astrophysics Supplement 130 (2): 215–222, doi:10.1051/aas:1998226, Bibcode: 1998A&AS..130..215S 
  14. ↑ Abt, Helmut A.; Morrell, Nidia I. (July 1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement 99: 135, doi:10.1086/192182, Bibcode: 1995ApJS...99..135A 
  15. ↑ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. https://flagspot.net/flags/br_astro.html. 



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