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]

References

  1. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
  3. 1 2 Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239. ISSN 0004-6256. S2CID 121672252.
  4. ↑ Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
  5. ↑ Corben, P. M. (April 1971). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of South Africa. 30 (4): 37. Bibcode:1971MNSSA..30...37C. ISSN 0024-8266.
  6. 1 2 Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN 1562-6881. ISSN 1063-7729. S2CID 125853869.
  7. 1 2 Gontcharov, G. A. (November 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. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  8. 1 2 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  9. 1 2 Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (20 December 2021). "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs". Astronomy & Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. eISSN 1432-0746. ISSN 0004-6361. S2CID 237605138.
  10. 1 2 3 Koen, C.; Laney, D. (21 January 2000). "Rapidly oscillating M giant stars?". Monthly Notices of the Royal Astronomical Society. 311 (3): 636–648. Bibcode:2000MNRAS.311..636K. doi:10.1046/j.1365-8711.2000.03127.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 122553846.
  11. 1 2 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361. S2CID 6077801.
  12. 1 2 McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 118665352.
  13. 1 2 Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
  14. ↑ Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  15. ↑ "V718 Corona Australis". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved March 17, 2023.
  16. ↑ Eggleton, P. P.; Tokovinin, A. A. (11 September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
  17. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.
  18. ↑ EAS (1997). "The HIPPARCOS and TYCHO catalogues". Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. ESA SP Series. Noordwijk, Netherlands: ESA Publications Division. 1200. Bibcode:1997ESASP1200.....E. ISBN 9290923997. Retrieved 18 March 2023.
  19. ↑ Eggen, O. J. (September 1973). "The classification of intrinsic variables. IV. Very-small-amplitude, very-short-period red variables". The Astrophysical Journal. 184: 793. Bibcode:1973ApJ...184..793E. doi:10.1086/152371. eISSN 1538-4357. ISSN 0004-637X. S2CID 120021304.
  20. ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars. 4659: 1. Bibcode:1999IBVS.4659....1K. ISSN 0374-0676.
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