R Coronae Australis

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R Coronae Australis
R Coronae Australis region.jpg
A colour photo of the R Coronae Australis region in the southern Milky Way.
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  mas [5]
Distance 152.9+8.1
−7.3 [6]   pc
Absolute magnitude  (MV)−0.30 [7]
Orbit
Period (P)45±2 [8] yr
Semi-major axis (a)0.1968±0.0045 [8] "
(27-28 AU [6] )
Eccentricity (e)0.4 [6]
Inclination (i)70 [6] °
Details
A
Mass 3.5 [7]   M☉
Radius 6.2 [7]   R☉
Luminosity 132 [7]   L☉
Temperature 9,550 [7]   K
Age 1+1
−0.5 [6]   Myr
B
Mass 0.3 - 0.55 [6]   M☉
Surface gravity (log g)3.45±0.06 [6]   cgs
Temperature 3,650 - 3,870 [6]   K
Other designations
CD−37°13027, HIP  93449, Wray 15-1887
Database references
SIMBAD data
A visual band light curve for R Coronae Australis, plotted from ASAS data RCrALightCurve.png
A visual band light curve for R Coronae Australis, plotted from ASAS data

R Coronae Australis (R CrA) is a variable binary system in the constellation Corona Australis. [2] [8] It has varied between magnitudes 10 and 14.36. [10] A small reflection/emission nebula NGC 6729 extends from the star towards SE. It is also the brightest feature of the Coronet Cluster, therefore sometimes called R CrA Cluster.

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. [11] 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] Examination of other objects known to be in the same star-forming region gives a distance of 152.9+8.1
−7.3  pc , suggesting an error in the Gaia parallax for R CrB itself. [6]

Johann Friedrich Julius Schmidt discovered that R Coronae Australis is a variable star, in 1865. It appeared with its variable star designation in Annie Jump Cannon's 1907 work Second Catalogue of Variable Stars. [12]

A companion to the star was proposed 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. [8] The companion was later directly observed to be a red dwarf with a mass between 0.3  M☉ and 0.55 M☉. [6] It has also been proposed that the primary component is itself a close binary. [7]

References

  1. 1 2 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. S2CID   18759600.
  2. 1 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. S2CID   119231169.
  5. 1 2 3 4 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. 1 2 3 4 5 6 7 8 9 10 Mesa, D.; et al. (2019). "Exploring the R CrA environment with SPHERE. Discovery of a new stellar companion". Astronomy and Astrophysics. 624. arXiv: 1902.02536 . Bibcode:2019A&A...624A...4M. doi:10.1051/0004-6361/201834682. S2CID   155675656.
  7. 1 2 3 4 5 6 Sissa, E.; Gratton, R.; Alcalà, J. M.; Desidera, S.; Messina, S.; Mesa, D.; d'Orazi, V.; Rigliaco, E. (2019). "The origin of R CrA variability. A complex triple system hosting a disk". Astronomy and Astrophysics. 630. arXiv: 1908.07256 . Bibcode:2019A&A...630A.132S. doi:10.1051/0004-6361/201936101. S2CID   201103714.
  8. 1 2 3 4 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. S2CID   102491664.
  9. ↑ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  10. ↑ BSJ (14 June 2010). "R Coronae Australis". AAVSO Website. American Association of Variable Star Observers . Retrieved 29 June 2014.
  11. ↑ 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
  12. ↑ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory. 55: 1–94. Bibcode:1907AnHar..55....1C . Retrieved 8 February 2025.
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