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 | |
Database references | |
SIMBAD | 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]
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]