Astronomy:Theta Coronae Australis

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Short description: Star in the constellation Corona Australis
θ Coronae Australis
Location of Theta CrA (circled)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Corona Australis[1]
Right ascension  18h 33m 30.18577s[2]
Declination −42° 18′ 45.0297″[2]
Apparent magnitude (V) 4.61±0.01[3]
Characteristics
Spectral type G8 III[4]
U−B color index +0.76[5]
B−V color index +1.02[5]
Astrometry
Radial velocity (Rv)−2.1±2.8[6] km/s
Proper motion (μ) RA: +32.046[2] mas/yr
Dec.: −20.932[2] mas/yr
Parallax (π)6.1673 ± 0.1535[2] mas
Distance530 ± 10 ly
(162 ± 4 pc)
Absolute magnitude (MV)−1.54[1]
Details
Mass4.45±0.22[7] M☉
Radius29.1±1.5[8] R☉
Luminosity411+21−19[2] L☉
Surface gravity (log g)2.50[9] cgs
Temperature4,907±59[10] K
Metallicity [Fe/H]+0.00[2] dex
Rotational velocity (v sin i)12±1[11] km/s
Other designations
Bie, θ CrA, CD−42°13378, CPD−42°8423, FK5 697, GC 25313, HD 170845, HIP 90982, HR 6951, SAO 229111[12][13]
Database references
SIMBADdata

Theta Coronae Australis, also named Bie,[14] is a solitary yellow-hued star[15] located in the southern constellation of Corona Australis. Its Bayer designation is Latinized from θ Coronae Australis, and abbreviated Theta CrA or θ CrA. This star has an apparent magnitude of 4.61, making it readily visible to the naked eye. Gaia DR3 parallax measurements place it 530 light years away. It is drifting closer with a heliocentric radial velocity of roughly −2 km/s. At its current distance, Theta CrA's brightness is diminished by three-tenths of a magnitudes due to interstellar dust.[16] It has an absolute magnitude of −1.54.[1]

This is an evolved red giant with a stellar classification of G8 III.[4] It has 4.45 times the mass of the Sun[7] but has expanded to 29.1 times the solar radius.[8] It radiates 411 times the luminosity of the Sun[2] from its enlarged photosphere at an effective temperature of 4,907 K.[10] Theta CrA has a solar metallicity.[2] Unlike most giant stars of this type, Theta CrA has an unusually high rate of rotation with a projected rotational velocity of 12 km/s.[11] The star may have an infrared excess, suggesting the presence of a circumstellar disk of dust.[17] One possible explanation is that it may have engulfed a nearby giant planet, such as a hot Jupiter.[17]

In Chinese astronomy, this star is part of the constellation Biē (鳖, River Turtle). The IAU Working Group on Star Names adopted the name Bie for this star on 13 August 2026, after this Chinese constellation.[14]

References

  1. ↑ 1.0 1.1 1.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ Høg, E. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  4. ↑ 4.0 4.1 Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars Volume II: Declinations −53° to −40°. Bibcode: 1978mcts.book.....H. 
  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: 99–110. Bibcode: 1966CoLPL...4...99J. 
  6. ↑ Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.0 7.1 Kervella, Pierre et al. (20 December 2021). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics 657: A7. doi:10.1051/0004-6361/202142146. ISSN 0004-6361. Bibcode: 2022A&A...657A...7K. 
  8. ↑ 8.0 8.1 Kervella, P. et al. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  9. ↑ Lafrasse, Sylvain et al. (16 July 2010). "Building the 'JMMC Stellar Diameters Catalog' using SearchCal". Optical and Infrared Interferometry II. 7734. pp. 77344E. doi:10.1117/12.857024. Bibcode: 2010SPIE.7734E..4EL. 
  10. ↑ 10.0 10.1 Blackwell, D. E.; Lynas-Gray, A. E. (May 1998). "Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method". Astronomy and Astrophysics Supplement Series 129 (3): 505–515. doi:10.1051/aas:1998202. ISSN 0365-0138. Bibcode: 1998A&AS..129..505B. 
  11. ↑ 11.0 11.1 De Medeiros, J. R. et al. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars". Astronomy & Astrophysics 561: A126. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode: 2014A&A...561A.126D. 
  12. ↑ "* tet CrA". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+tet+CrA. 
  13. ↑ Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino 1. Bibcode: 1879RNAO....1.....G. 
  14. ↑ 14.0 14.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 
  15. ↑ Eggleton, P. P.; Tokovinin, A. A. (11 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. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E. 
  16. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  17. ↑ 17.0 17.1 da Silva, R. Rodrigues et al. (4 March 2015). "On the Nature of Rapidly Rotating Single Evolved Stars". The Astrophysical Journal 801 (1): 54. doi:10.1088/0004-637X/801/1/54. Bibcode: 2015ApJ...801...54R. 



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