Zeta Coronae Australis

Zeta Coronae Australis (ζ Coronae Australis) is a solitary,[10] blue-white hued star located in the southern constellation Corona Australis. With an apparent visual magnitude of +4.75,[2] it is sufficiently bright to be viewed with the naked eye. Based upon an annual parallax shift of 16.89 mas as seen from Earth,[1] this star is located around 193 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.15 due to interstellar dust.[4]

Zeta Coronae Australis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Corona Australis
Right ascension 19h 03m 06.87698s[1]
Declination −42° 05′ 42.3858″[1]
Apparent magnitude (V) +4.75[2]
Characteristics
Spectral type B9.5 Vann[3]
U−B color index −0.07[2]
B−V color index −0.02[2]
Astrometry
Proper motion (μ) RA: +56.41[1] mas/yr
Dec.: −46.43[1] mas/yr
Parallax (π)16.89 ± 0.28[1] mas
Distance193 ± 3 ly
(59.2 ± 1.0 pc)
Absolute magnitude (MV)+0.76[4]
Details[5]
Mass2.92 M☉
Radius2.11[6] R☉
Luminosity51[7] L☉
Surface gravity (log g)4.21±0.14 cgs
Temperature12,039±409 K
Metallicity [Fe/H]−0.21[8] dex
Rotational velocity (v sin i)308 km/s
Age76 Myr
Other designations
ζ CrA, CD−42° 13855, GC 26165, HD 176638, HIP 93542, HR 7188, SAO 229461[9]
Database references
SIMBADdata

This is a B-type main sequence star with a stellar classification of B9.5 Vann.[3] The suffix notation 'nn' indicates there are broad spectrum absorption lines in the spectrum associated with its rotation period. At the estimated age of just 76 million years, it is spinning rapidly with a projected rotational velocity of 308 km/s.[5] The star has 2.92 times the mass of the Sun and 2.11[6] times the Sun's radius. It is radiating 51[7] times the Sun's luminosity from its photosphere at an effective temperature of about 12,039 K.[5]

There is an infrared excess at a wavelength of 60 μm. This suggests there is a circumstellar disk of dust with a temperature of 120 K orbiting 34 AU from the host star.[6]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Johnson, H. L.; et al. (1966), "Ubvrijkl Photometry of the Bright Stars", Communications of the Lunar and Planetary Laboratory, 4: 99, Bibcode:1966CoLPL...4...99J.
  3. Gray, R. O.; Garrison, R. F. (December 1987), "The Early A-Type Stars: Refined MK Classification, Confrontation with Stroemgren Photometry, and the Effects of Rotation", Astrophysical Journal Supplement, 65: 581, Bibcode:1987ApJS...65..581G, doi:10.1086/191237.
  4. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035.
  5. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  6. Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912.
  7. Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  8. Saffe, C.; Gómez, M.; Pintado, O.; González, E. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260.
  9. "zet CrA". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-26.
  10. Eggleton, P. P.; Tokovinin, A. A. (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.
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