V718 Coronae Australis

V718 Coronae Australis
Location of V718 CrA (circled)
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]
Distance630 ± 10 ly
(193 ± 3 pc)
Absolute magnitude (MV)−1.03[8]
Details
Mass1.45[9] or 2[10] M☉
Radius101±5[11] R☉
Luminosity1,001[12] L☉
Temperature3,698±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
SIMBADdata

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]

A light curve for V718 Coronae Australis, plotted from Hipparcos data[18]

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]

  1. ^ a b c d e Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Tycho2000 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Eggen1992 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Houk1978 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Corben1971 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Kervella2021 was invoked but never defined (see the help page).
  10. ^ a b c Cite error: The named reference Koen2000 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Kervella2004 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference McDonald2012 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Stassun2019 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Gould1879 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Gontcharov2017 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference CDS was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Eggen1973 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Kazarovets1999 was invoked but never defined (see the help page).