R Coronae Australis

R Coronae Australis

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]
Distance152.9+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
Mass3.5[7] M☉
Radius6.2[7] R☉
Luminosity132[7] L☉
Temperature9,550[7] K
Age1+1
−0.5[6] Myr
B
Mass0.3 - 0.55[6] M☉
Surface gravity (log g)3.45±0.06[6] cgs
Temperature3,650 - 3,870[6] K
Other designations
CD−37°13027, HIP 93449, Wray 15-1887
Database references
SIMBADdata
A visual band light curve for R Coronae Australis, plotted from ASAS data[9]

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]

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]

  1. ^ a b Cite error: The named reference HIP was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  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. ^ Cite error: The named reference RV was invoked but never defined (see the help page).
  5. ^ a b c d 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. ^ a b c d e f g h i j 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. ^ a b c d e f 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. ^ a b c d 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. ^ Cite error: The named reference ASASServer was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference AAVSOR was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference aaa449_3_1233 was invoked but never defined (see the help page).