Theta Coronae Australis

Theta Coronae Australis (Theta CrA), Latinized from θ Coronae Australis, is a solitary yellow-hued star[14] located in the southernconstellation Corona Australis. It 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 and it is currently drifting closer with a somewhat constrained heliocentric radial velocity of −2.1 km/s. At its current distance, Theta CrA's brightness is diminished by three-tenths of a magnitudes due to interstellar dust.[15] It has an absolute magnitude of −1.54.[6]

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

This is an evolved red giant with a stellar classification of G8 III.[3] 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[1] from its enlarged photosphere at an effective temperature of 4,907 K.[10] Theta CrA has a solar metallicity;[1] 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 also have infrared excess, suggesting the presence of a circumstellar disk.[16] One possible explanation is that it may have engulfed a nearby giant planet, such as a hot Jupiter.[16]

References
  1. 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. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars Volume II: Declinations −53° to −40°. Bibcode:1978mcts.book.....H.
  4. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  5. 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. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  6. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  7. Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (20 December 2021). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. eISSN 1432-0746. ISSN 0004-6361.
  8. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361.
  9. Lafrasse, Sylvain; Mella, Guillaume; Bonneau, Daniel; Duvert, Gilles; Delfosse, Xavier; Chesneau, Olivier; Chelli, Alain (16 July 2010). "Building the 'JMMC Stellar Diameters Catalog' using SearchCal". Optical and Infrared Interferometry II. Vol. 7734. pp. 77344E. arXiv:1009.0137. Bibcode:2010SPIE.7734E..4EL. doi:10.1117/12.857024. S2CID 32097037.
  10. 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. Bibcode:1998A&AS..129..505B. doi:10.1051/aas:1998202. eISSN 1286-4846. ISSN 0365-0138.
  11. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
  12. 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.
  13. "* tet CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 17 August 2017.
  14. 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. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
  15. 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. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711.
  16. da Silva, R. Rodrigues; Canto Martins, B. L.; De Medeiros, J. R. (4 March 2015). "On the Nature of Rapidly Rotating Single Evolved Stars". The Astrophysical Journal. 801 (1): 54. arXiv:1503.03447. Bibcode:2015ApJ...801...54R. doi:10.1088/0004-637X/801/1/54. eISSN 1538-4357. S2CID 119271718.
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