V692 Coronae Australis

V692 Coronae Australis (HD 166596; HR 6804; 3 G. CrA), or simply V692 CrA, is a whitish-blue hued variable star located in the southern constellation Corona Australis. It has a maximum apparent magnitude of 5.46,[2] making it faintly visible to the naked eye. The object is located relatively far at a distance of approximately 1,900 light years based on Gaia DR3 parallax measurements,[1] but it is approaching the Solar System with a fairly constrained heliocentric radial velocity of −15.3 km/s.[8] At its current distance, V692 CrA's brightness is heavily diminished by 0.46 magnitudes due to extinction due to interstellar dust.[18] Its absolute magnitude depends on the source: Westin (1985) gave a value of −6.44[9] while the extended Hipparcos catalogue gave a value of −2.26.[10]

A light curve for V692 Coronae Australis, plotted from Hipparcos data[19]
V692 Coronae Australis
Location of V692 CrA (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Corona Australis
Right ascension 18h 13m 12.69843s[1]
Declination −41° 20′ 09.9972″[1]
Apparent magnitude (V) 5.46[2] (5.46 - 5.51)[3]
Characteristics
Spectral type B2 III[4] or B1.5 IIIp[5]
B−V color index −0.17[6]
Variable type SX Arietis[7]
Astrometry
Radial velocity (Rv)−15.3±2.8[8] km/s
Proper motion (μ) RA: −2.050 mas/yr[1]
Dec.: −6.210 mas/yr[1]
Parallax (π)1.7423 ± 0.0977 mas[1]
Distance1,900 ± 100 ly
(570 ± 30 pc)
Absolute magnitude (MV)−6.44[9] or −2.26[10]
Details
Mass7.35±0.48[11] M☉
Radius12.6±0.7[12] R☉
Luminosity (bolometric)4,181[11] L☉
Surface gravity (log g)3.52+0.33
−0.14[1] cgs
Temperature17,061+1,474
−1,357[13] K
Rotational velocity (v sin i)212±9[14] km/s
Age31.6±5.1[15] Myr
Other designations
3 G. Corona Australis[16], V692 CrA, CD−41°12534, CPD−41°8620, GC 24824, HD 166596, HIP 89290, HR 6804, SAO 228815[17]
Database references
SIMBADdata

Astronomers Carlos and Mercedes Jaschek along with a colleague listed HD 166596 as a Be star in 1964.[20] However, its status as an Ap star was not observed until 1979 by astronomers N. Vogt and A.M Faundez.[21] A year later, HD 166596 was observed to be variable and it had a period of 1.67 days.[22] In 1981, its variability was confirmed and it was given the variable star designation V692 Coronae Australis—the 692nd variable star in Corona Australis.[23] The star might have a shorter period of 49.8 hours.[7]

V692 CrA has a stellar classification of B2 III[4] or B1.5 IIIp,[5] both indicating that it is a slightly evolved B-type giant star. The second classification indicates that V692 CrA has peculiarities in its spectrum. It has 7.35 times the mass of the Sun[11] and 12.6 times the Sun's radius.[12] It radiates at a bolometric luminosity 4,181 times that of the Sun[11] from its photosphere at an effective temperature of 17,061 K.[13] V692 CrA is estimated to be 31.6 million years old[15] and it spins rapidly with a projected rotational velocity of 212 km/s.[14]

References
  1. 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. 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. "VSX : Detail for V0692 CrA". www.aavso.org.
  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. Rountree, Janet; Sonneborn, George (March 1991). "Criteria for the spectral classification of B stars in the ultraviolet". The Astrophysical Journal. 369: 515. Bibcode:1991ApJ...369..515R. doi:10.1086/169781. eISSN 1538-4357. ISSN 0004-637X. S2CID 118640556.
  6. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J. S2CID 118307502.
  7. 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.
  8. 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.
  9. Westin, T. N. G. (April 1985). "The local system of early type stars. Spatial extent and kinematics". Astronomy and Astrophysics Supplement Series. 60: 99–134. Bibcode:1985A&AS...60...99W. ISSN 0365-0138. S2CID 119020376.
  10. 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.
  11. Hohle, M.M.; Neuhäuser, R.; Schutz, B.F. (April 2010). "Masses and luminosities of O- and B-type stars and red supergiants". Astronomische Nachrichten. 331 (4): 349–360. arXiv:1003.2335. Bibcode:2010AN....331..349H. doi:10.1002/asna.200911355. eISSN 1521-3994. ISSN 0004-6337. S2CID 111387483.
  12. 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.
  13. Gulati, R. K.; Malagnini, M. L.; Morossi, C. (October 1989). "Empirical temperature calibrations for early-type stars". Astronomy and Astrophysics Supplement Series. 80: 73–88. Bibcode:1989A&AS...80...73G. ISSN 0365-0138. S2CID 115777506.
  14. Brown, A. G. A.; Verschueren, W. (March 1997). "High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2". Astronomy & Astrophysics. 319: 811–838. arXiv:astro-ph/9608089. Bibcode:1997A&A...319..811B. ISSN 0004-6361. S2CID 118925453.
  15. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (October 12, 2010). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. Oxford University Press (OUP). 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. ISSN 0035-8711. S2CID 118629873.
  16. 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.
  17. "V* V692 CrA". SIMBAD. Centre de données astronomiques de Strasbourg.
  18. 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.
  19. 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:1997HIP...C......0E. ISBN 9290923997. Retrieved 15 October 2022.
  20. Jaschek, C.; Jaschek, M.; Kucewicz, B. (1964). "A Survey of Southern Be Stars". Zeitschrift für Astrophysik. 59: 108. Bibcode:1964ZA.....59..108J. ISSN 0372-8331. S2CID 117724232.
  21. Vogt, N.; Faundez, A. M. (1 June 1979). "Photoelectric observations of peculiar A and related stars I: Strömgren photometry of 341 Ap stars". Astronomy and Astrophysics Supplement Series. 36: 477–484. Bibcode:1979A&AS...36..477V. ISSN 0365-0138.
  22. Renson, P.; Manfroid, J. (March 1980). "Nouvelle Recherche de Periodes d'etoiles Ap Observees a l'ESO-IV". Information Bulletin on Variable Stars. 1755: 1. Bibcode:1980IBVS.1755....1R. ISSN 0374-0676.
  23. Kholopov, P. N.; Samus', N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (November 1981). "66th Name-List of Variable Stars". Information Bulletin on Variable Stars. 2042: 1. Bibcode:1981IBVS.2042....1K. ISSN 0374-0676.
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