Astronomy:V718 Coronae Australis

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Short description: Slow irregular variable; Corona Australis
V718 Coronae Australis
Corona Australis constellation map.svg
Red circle.svg
Location of V718 CrA (circled)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
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[1] mas/yr
Dec.: −43.168[1] mas/yr
Parallax (π)5.1919 ± 0.0901[1] mas
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
V718 CrA, CD−43°12699, CPD−43°8703, GC 25488, HD 171697, HIP 91494, HR 6991, SAO 229172[14]
Database references
SIMBADdata

V718 Coronae Australis (HD 171697; HR 6991; V718 CrA) is a solitary variable star[15] 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[16] and it has an absolute magnitude of −1.03.[8]

A light curve for V718 Coronae Australis, plotted from Hipparcos data[17]

This object was first noticed to be potentially variable by Olin J. Eggen in 1973.[18] Its variability was confirmed in 1999 after subsequent observations and was given the variable star designation V718 Coronae Australis.[19] 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. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". The Astronomical Journal 104: 275. doi:10.1086/116239. ISSN 0004-6256. Bibcode: 1992AJ....104..275E. 
  4. ↑ Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. 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. ISSN 0024-8266. Bibcode: 1971MNSSA..30...37C. 
  6. ↑ 6.0 6.1 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. doi:10.1134/S1063772917010085. ISSN 1063-7729. Bibcode: 2017ARep...61...80S. 
  7. ↑ 7.0 7.1 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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  8. ↑ 8.0 8.1 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  9. ↑ 9.0 9.1 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. doi:10.1051/0004-6361/202142146. ISSN 0004-6361. Bibcode: 2022A&A...657A...7K. 
  10. ↑ 10.0 10.1 10.2 Koen, C.; Laney, D. (21 January 2000). "Rapidly oscillating M giant stars?". Monthly Notices of the Royal Astronomical Society 311 (3): 636–648. doi:10.1046/j.1365-8711.2000.03127.x. ISSN 0035-8711. Bibcode: 2000MNRAS.311..636K. 
  11. ↑ 11.0 11.1 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. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  12. ↑ 12.0 12.1 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. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. Bibcode: 2012MNRAS.427..343M. 
  13. ↑ 13.0 13.1 Stassun, Keivan G. et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. Bibcode: 2019AJ....158..138S. 
  14. ↑ "V718 Corona Australis". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=V718+Corona+Australis. 
  15. ↑ 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. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E. 
  16. ↑ 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. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
  17. ↑ 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. ISBN 9290923997. Bibcode: 1997ESASP1200.....E. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats. Retrieved 18 March 2023. 
  18. ↑ Eggen, O. J. (September 1973). "The classification of intrinsic variables. IV. Very-small-amplitude, very-short-period red variables". The Astrophysical Journal 184: 793. doi:10.1086/152371. ISSN 0004-637X. Bibcode: 1973ApJ...184..793E. 
  19. ↑ 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. ISSN 0374-0676. Bibcode: 1999IBVS.4659....1K. 
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