Delta Coronae Borealis, Latinized from δ Coronae Borealis, is a variable star in the constellation Corona Borealis. Its apparent magnitude varies regularly between apparent magnitude 4.57 and 4.69, and it is around 167 light-years distant. It is visible to the naked eye.

A visual band light curve for Delta Coronae Borealis, plotted from data published by Fernie (1991).[9] The 59 day rotation period is shown in red.

δ Coronae Borealis is a yellow giant star of spectral type G3.5III that is around 2.4 times as massive as the Sun and has swollen to 7.4 times its radius. It has a surface temperature of 5180 K.[10]

For most of its existence, Delta Coronae Borealis was a blue-white main sequence star of spectral type B before it ran out of hydrogen fuel in its core. Its luminosity and spectrum suggest it has just crossed the Hertzsprung gap, having finished burning core hydrogen and now begun burning hydrogen in its shell.[11][1] However, one recent paper gives a 64% chance that it has begin fusing core helium and is on the horizontal branch.[12] It is a strong source of X-rays due to its hot corona.[7]

In 1989, it was noticed that the brightness of δ Coronae Borealis is not constant. Approximately every 45 days, its brightness changes sinusoidally between 4.57 and 4.69, too small to be noticed without close monitoring. The evolutionary state of the star and its probably rotation period mean that the variations may be due to its rotation with different parts of the surface having spots or different temperatures. This would make it an RS Canum Venaticorum variable.[13] The period has since been refined to 59 days and this is now accepted as the star's rotation period.[7]

References

  1. ^ a b c d e f 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. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  3. ^ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  4. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data., 0 (1986): 0. Bibcode:1986EgUBV........0M.
  5. ^ Niedzielski, A.; Deka-Szymankiewicz, B.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (2016). "The Penn State - Toruń Centre for Astronomy Planet Search stars". Astronomy and Astrophysics. 585: A73. Bibcode:2016A&A...585A..73N. doi:10.1051/0004-6361/201527362.
  6. ^ a b c d e Niedzielski, A.; Deka-Szymankiewicz, B.; Adamczyk, M.; Adamów, M.; Nowak, G.; Wolszczan, A. (2016). "The Penn State - Toruń Centre for Astronomy Planet Search stars". Astronomy and Astrophysics. 585: A73. Bibcode:2016A&A...585A..73N. doi:10.1051/0004-6361/201527362.
  7. ^ a b c d e f g Gondoin, P. (2005). "The X-ray activity of the slowly rotating G giant δ CrB". Astronomy and Astrophysics. 431 (3): 1027–1035. Bibcode:2005A&A...431.1027G. doi:10.1051/0004-6361:20041991.
  8. ^ "del CrB". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 February 2017.
  9. ^ Fernie, J. D. (October 1991). "R Coronae Borealis and Delta Coronae Borealis in 1990". Publications of the Astronomical Society of the Pacific. 103: 1091–1093. Bibcode:1991PASP..103.1091F. doi:10.1086/132930. S2CID 120378390.
  10. ^ Gondoin, P. (2005). "The X-ray activity of the slowly rotating G giant δ CrB". Astronomy & Astrophysics. 431 (3): 1027–35. Bibcode:2005A&A...431.1027G. doi:10.1051/0004-6361:20041991.
  11. ^ Berdyugina, S. V. (1994). "Li and CNO abundances in the atmospheres of stars evolving to the red-giant branch". Astronomy Letters. 20 (5): 631. Bibcode:1994AstL...20..631B.
  12. ^ Stock, Stephan; Reffert, Sabine; Quirrenbach, Andreas (2018). "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search". Astronomy and Astrophysics. 616: A33. arXiv:1805.04094. Bibcode:2018A&A...616A..33S. doi:10.1051/0004-6361/201833111.
  13. ^ Fernie, J. D. (1987). "Delta Coronae Borealis : A chromospherically active giant ?". Publications of the Astronomical Society of the Pacific. 99: 183. Bibcode:1987PASP...99..183F. doi:10.1086/131975.
Allikas: https://en.wikipedia.org/wiki/Delta_Coronae_Borealis
No tags for this post.