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S Coronae Borealis (S CrB) is a Mira variable star in the constellation Corona Borealis. Its apparent magnitude varies between 5.3 and 13.6, with a period of 360 days—just under a year. Within the constellation, it lies to the west of Theta Coronae Borealis, and around 1 degree southeast of the eclipsing binary star U Coronae Borealis.

Variability

S Coronae Borealis was discovered to vary in brightness by German amateur astronomer Karl Ludwig Hencke in 1860. It was classified as a long period variable star as other similar objects were discovered, and later as a Mira variable. The maximum range of variation is from magnitude 5.3 to 13.6 although individual maxima and minima can vary in brightness. The period of 360 days is fairly predictable.

Properties

S Coronae Borealis is a cool red giant on the asymptotic giant branch (AGB). It pulsates, which causes its radius and temperature to change. One calculation found a temperature range of 2,350 K to 2,600 K, although a more modern calculation gives a temperature of 2,864 K. Similarly a calculation of the varying radius gives 537 to 664 R_☉ although a modern calculation of the radius gives 308 R_☉. The bolometric luminosity varies much less than the visual magnitude and is estimated to be 5,623 L_☉. Its parallax has been measured by very-long-baseline interferometry (VLBI), yielding a result of 2.39 ± 0.17 millarcseconds, which converts to a distance of 1300 ± 100 light-years.

The masses of AGB stars are poorly known and cannot be calculated from their physical properties, but they can be estimated using asteroseismology. The pulsations of S Coronae Borealis lead to a mass estimate of 1.34 times that of the Sun.

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. S2CID 18759600.
2. ^ VSX (4 January 2010). "S Coronae Borealis". AAVSO Website. American Association of Variable Star Observers. Retrieved 27 June 2014.
3. Bieging, John H.; Schmidt, Gary D.; Smith, Paul S.; Oppenheimer, Benjamin D. (2006). "Optical Spectropolarimetry of Asymptotic Giant Branch and Post–Asymptotic Giant Branch Stars". The Astrophysical Journal. 639 (2): 1053. Bibcode:2006ApJ...639.1053B. doi:10.1086/499772.
4. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
5. ^ Vlemmings, W. H. T.; Van Langevelde, H. J. (2007). "Improved VLBI astrometry of OH maser stars". Astronomy and Astrophysics. 472 (2): 547. arXiv:0707.0918. Bibcode:2007A&A...472..547V. doi:10.1051/0004-6361:20077897. S2CID 18816871.
6. Feijth, H. (1977). "The variable S Coronae Borealis". Zenit. 4: 451. Bibcode:1977Zenit...4..451F.
7. ^ Takeuti, Mine; Nakagawa, Akiharu; Kurayama, Tomoharu; Honma, Mareki (2013). "A Method to Estimate the Masses of Asymptotic Giant Branch Variable Stars". Publications of the Astronomical Society of Japan. 65 (3): 60. Bibcode:2013PASJ...65...60T. doi:10.1093/pasj/65.3.60.
8. ^ Wallerstein, G. (1977). "Are long-period variables really pulsating". Journal of the Royal Astronomical Society of Canada. 71: 298. Bibcode:1977JRASC..71..298W.
9. McDonald, I.; De Beck, E.; Zijlstra, A. A.; Lagadec, E. (2018). "Pulsation-triggered dust production by asymptotic giant branch stars". Monthly Notices of the Royal Astronomical Society. 481 (4): 4984. arXiv:1809.07965. Bibcode:2018MNRAS.481.4984M. doi:10.1093/mnras/sty2607. S2CID 118969263.
10. Plotner, Tammy; Vogt, Ken (2009). The Night Sky Companion: A Yearly Guide to Sky-Watching 2009. The Patrick Moore Practical Astronomy Series. Springer Science & Business Media. p. 194. ISBN 978-0387795096.
11. Hamel, Jürgen (2007). "Hencke, Karl Ludwig". The Biographical Encyclopedia of Astronomers. p. 481. doi:10.1007/978-0-387-30400-7_596. ISBN 978-0-387-31022-0.
12. Campbell, Leon (1926). "Maxima and minima of two hundred and seventy-two long period variable stars during the years 1900 – 1920". Annals of Harvard College Observatory. 79: 87. Bibcode:1926AnHar..79...87C.
13. Cotton, W. D.; Mennesson, B.; Diamond, P. J.; Perrin, G.; Coudé Du Foresto, V; Chagnon, G.; Van Langevelde, H. J.; Ridgway, S.; Waters, R.; Vlemmings, W.; Morel, S.; Traub, W.; Carleton, N.; Lacasse, M. (2004). "VLBA observations of SiO masers towards Mira variable stars" (PDF). Astronomy and Astrophysics. 414: 275–288. Bibcode:2004A&A...414..275C. doi:10.1051/0004-6361:20031597.

• Corona Borealis
• Mira variables
• Objects with variable star designations
• M-type giants
• Henry Draper Catalogue objects
• Durchmusterung objects
• Hipparcos objects
• Emission-line stars