Gamma Trianguli Australis

Gamma Trianguli Australis
Location of γ Trianguli Australis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Triangulum Australe
Right ascension 15h 18m 54.58129s[1]
Declination –68° 40′ 46.3680″[1]
Apparent magnitude (V) +2.87[2]
Characteristics
Evolutionary stage Subgiant or giant star[3]
Spectral type A1III[3]
U−B color index –0.02[4]
B−V color index +0.00[4]
Astrometry
Radial velocity (Rv)–3.0[2] km/s
Proper motion (μ) RA: –65.816 mas/yr[1]
Dec.: –31.187 mas/yr[1]
Parallax (π)17.1809 ± 0.3327 mas[1]
Distance190 ± 4 ly
(58 ± 1 pc)[1]
Absolute magnitude (MV)−0.89[5]
Details[3]
Mass3.04 M☉
Radius6.5 or 7 R☉
Luminosity249[6] L☉
Surface gravity (log g)3.39[7] cgs
Temperature8,225 K
Rotational velocity (v sin i)199[8] km/s
Age350 Myr
Other designations
γ TrA, CD−68° 1503, FK5 560, HD 135382, HIP 74946, HR 5671, SAO 253097[9]
Database references
SIMBADdata

Gamma Trianguli Australis, Latinized from γ Trianguli Australis, is a single,[10] 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 190 light-years (58 parsecs) from Earth.[1]

Characteristics

The spectrum of this star matches a stellar classification of A1 III, which identifies it as a giant star. It could be also a subgiant.[3] An unusual abundance of the element europium demonstrates it to be a peculiar, or Ap star.[11] However, its classification as a chemically peculiar star is doubtful.[3] Most stars of this type are slow rotators,[12] but Gamma Trianguli Australis displays a very high rate of rotation with a projected rotational velocity of 199 km s−1.[8]

At a mass of 3.04 solar masses, Gamma Trianguli Australis was a late B-type star (B8V/B9V) in the main sequence. Being 350 million years old, it has recently begun its expansion towards a red giant. Its radius is either 6.5 R☉ (estimated using stellar isochrones) or 7 R☉ (measured).[3] The star is emitting a luminosity equivalent to 250 solar luminosities.[6] Its surface has an effective temperature of 8,225 K.[3] This is around 2,450 K hotter than the Sun[13] and gives it a white hue, typical of A-type stars.[14]

This star 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.[15]

Reported companion star

The Gaia Data Release 3 (Gaia DR3) reported Gamma Trianguli Australis as an astrometric binary with a period of 488 days (1.34 years). The companion star would be a red dwarf with a mass of 0.15 M☉ and a semimajor axis of 1.8 AU. However, a further study using the Very Large Telescope did not found any evidence of a companion.[3]

Modern legacy

γ TrA appears on the flag of Brazil, symbolising the state of Paraná.[16]

References

  1. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c 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, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
  3. ^ a b c d e f g h Waisberg, Idel; Klein, Ygal; Katz, Boaz (May 2024). "Hidden Companions to Intermediate-mass Stars. XIX. Spin–Orbit Misalignment and a 0.26M⊙, 1.8 au Companion in the Astrometric Binary Gamma Trianguli Australis*". Research Notes of the AAS. 8 (5): 131. doi:10.3847/2515-5172/ad4a7b. ISSN 2515-5172.
  4. ^ a b 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.
  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, S2CID 119257644.
  6. ^ a b Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
  7. ^ 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, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
  8. ^ a b 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, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298
  9. ^ "gam TrA -- Variable Star", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-04
  10. ^ 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  11. ^ Sokolov, N. A. (June 1998), "Effective temperatures of AP stars", Astronomy and Astrophysics Supplement, 130 (2): 215–222, Bibcode:1998A&AS..130..215S, doi:10.1051/aas:1998226
  12. ^ 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, Bibcode:1995ApJS...99..135A, doi:10.1086/192182
  13. ^ "Sun Fact Sheet". nssdc.gsfc.nasa.gov.
  14. ^ "The Colour of Stars". Australia National Telescope Facility. 6 March 2024. Retrieved 2024-05-27.
  15. ^ Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505
  16. ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website.