V718 Coronae Australis
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  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Corona Australis |
| Right ascension | 18h 39m 35.15900s[1] |
| Declination | −43° 11′ 09.1691″[1] |
| Apparent magnitude (V) | 5.43±0.01[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M2 III[4] |
| B−V color index | +1.63[5] |
| Variable type | LB:[6] |
| Astrometry | |
| Radial velocity (Rv) | 28.5±0.8[7] km/s |
| Proper motion (μ) | RA: −32.414 mas/yr[1] Dec.: −43.168 mas/yr[1] |
| Parallax (π) | 5.1919±0.0901 mas[1] |
| Distance | 630 ± 10 ly (193 ± 3 pc) |
| Absolute magnitude (MV) | −1.03[8] |
| Details | |
| Mass | 1.45[9] or 2[10] M☉ |
| Radius | 101±5[11] R☉ |
| Luminosity | 1,001[12] L☉ |
| Temperature | 3,698±122[13] K |
| Other designations | |
| 18 G. Coronae Australis[14], V718 CrA, CD−43°12699, CPD−43°8703, GC 25488, HD 171697, HIP 91494, HR 6991, SAO 229172[15] | |
| Database references | |
| SIMBAD | data |
V718 Coronae Australis (HD 171697; HR 6991; V718 CrA) is a solitary variable star[16] located in the southern constellation Corona Australis. It is faintly visible to the naked eye as a red-hued point of light with an apparent magnitude of 5.43.[2] Gaia DR3 parallax measurements imply a distance of 630 light years[1] and it is currently receding with a heliocentric radial velocity of 28.5 km/s.[7] At its current distance V718 CrA's brightness is diminished by 0.37 magnitudes due to interstellar dust[17] and it has an absolute magnitude of −1.03.[8]
This object was first noticed to be potentially variable by Olin J. Eggen in 1973.[19] Its variability was confirmed in 1999 after subsequent observations and was given the variable star designation V718 Coronae Australis.[20] Observations from Koen & Laney (2000) reveal that V718 CrA has two periods: one lasting 5.37 days and the other lasting 71.1 days.[10] It is a slow irregular variable of subtype Lb that fluctuates between 5.45 and 5.51 in the Hipparcos passband.[6]
V718 CrA has a stellar classification of M2 III, indicating that it is an evolved red giant. It is currently on the asymptotic giant branch,[3] fusing hydrogen and helium shells around an inert carbon core. It has 1.45 times the mass of the Sun[9] but it has expanded to 101 times the Sun's radius.[11] It radiates 1,001 times the luminosity of the Sun[12] from its enlarged photosphere at an effective temperature of 3,698 K.[13] Oscillation measurements from Koen & Laney (2000) yield a mass of 2 M☉.[10]
