R Coronae Australis

R Coronae Australis (R CrA) is a variable binary system in the constellation Corona Australis.[2][6] It has varied between magnitudes 10 and 14.36.[7] A small reflection/emission nebula NGC 6729 extends from the star towards SE.

R Coronae Australis
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Corona Australis
Right ascension  19h 01m 53.6503s[1]
Declination −36° 57′ 07.87″[1]
Apparent magnitude (V) +11.91
Characteristics
Spectral type B5IIIpe[2]
Variable type INSA[3]
Astrometry
Radial velocity (Rv)-36.0 ± 4.9[4] km/s
Proper motion (μ) RA: 1.582[5] mas/yr
Dec.: -30.835[5] mas/yr
Parallax (π)10.5361 ± 0.6971[5] mas
Distance310 ± 20 ly
(95 ± 6 pc)
Details
Mass3.5 M☉
Age1-3 million
0.3 million years
Orbit[6]
PrimaryR Coronae Australis A
CompanionR Coronae Australis B
Period (P)45±2 yr
Semi-major axis (a)0.1968±0.0045″
Other designations
CD−37° 13027, HIP 93449, Wray 15-1887
Database references
SIMBADdata

This star is moving toward the Solar System with a radial velocity of 36 km s−1. It was previously believed that in roughly 222,000 years, this system could have approached within 1.77 light-years (0.54 parsecs) of the Sun. However, the estimate had a considerable margin of error in it.[8] With the release of Gaia DR2, the star was determined to be 4 times further from the Sun than initially believed, constraining the approach to only 111 ± 31 light-years (34.0 ± 9.5 parsecs).[5]

A companion to the star was detected in 2019 with a mass between 0.1 and 1 Solar masses, depending on the characteristics of the stellar environment, orbiting the primary in 43–47 years.[6]

A colour photo of the R Coronae Australis region in the southern Milky Way.

References
  1. van Leeuwen, F. (13 August 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. "R Coronae Australis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 29 June 2014.
  3. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. Gontcharov, G. A. (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.
  5. 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.
  6. Cugno, G.; Quanz, S. P.; Launhardt, R.; Musso Barcucci, A.; Brems, S. S.; Cheetham, A.; Godoy, N.; Kennedy, G. M.; Henning, T.; Müller, A.; Olofsson, J.; Pepe, F.; Quirrenbach, A.; Reffert, S.; Rickman, E. L.; Ségransan, D. (3 April 2019). "ISPY – NaCo Imaging Survey for Planets around Young stars". Astronomy & Astrophysics. 624: A29. arXiv:1902.04092. doi:10.1051/0004-6361/201935142.
  7. BSJ (14 June 2010). "R Coronae Australis". AAVSO Website. American Association of Variable Star Observers. Retrieved 29 June 2014.
  8. Dybczyński, P. A. (April 2006), "Simulating observable comets. III. Real stellar perturbers of the Oort cloud and their output", Astronomy and Astrophysics, 449 (3): 1233–1242, Bibcode:2006A&A...449.1233D, doi:10.1051/0004-6361:20054284


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