| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 21m 23.9561s [1] |
| Declination | +31° 22′ 02.573″ [1] |
| Apparent magnitude (V) | 5.3 – 13.6 [2] |
| Characteristics | |
| Spectral type | M7e [3] |
| U−B color index | 0.36 [1] |
| B−V color index | 1.71 [1] |
| Variable type | Mira [2] |
| Astrometry | |
| Radial velocity (Rv) | -5.12 [4] km/s |
| Proper motion (μ) |
RA: -7.73
[1]
mas/
yr Dec.: -13.03 [1] mas/ yr |
| Parallax (π) | 2.39 ± 0.17 mas [5] |
| Distance | 418+21 −18 [5] pc |
| Absolute magnitude (MV) | -0.8±0.3 [6] |
| Details | |
| Mass | 1.34 [7] M☉ |
| Radius | 308 [7] (537–664) [8] R☉ |
| Luminosity | 5,897 [9] L☉ |
| Temperature | 2,864 [7] (2,350–2,600) [8] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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. [10]
Variability
S Coronae Borealis was discovered to vary in brightness by German amateur astronomer Karl Ludwig Hencke in 1860. [11] It was classified as a long period variable star as other similar objects were discovered, [12] and later as a Mira variable. [2] 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. [13]
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, [8] although a more modern calculation gives a temperature of 2,864 K. [7] Similarly a calculation of the varying radius gives 537 to 664 R☉ [8] although a modern calculation of the radius gives 308 R☉. [7] The bolometric luminosity varies much less than the visual magnitude and is estimated to be 5,623 L☉. [7] 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. [5]
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. [7]
References
- ^ a b c d e f 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.
- ^ a b c VSX (4 January 2010). "S Coronae Borealis". AAVSO Website. American Association of Variable Star Observers. Retrieved 27 June 2014.
- ^ 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.
- ^ 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.
- ^ a b c 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.
- ^ Feijth, H. (1977). "The variable S Coronae Borealis". Zenit. 4: 451. Bibcode: 1977Zenit...4..451F.
- ^ a b c d e f g 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.
- ^ a b c d Wallerstein, G. (1977). "Are long-period variables really pulsating". Journal of the Royal Astronomical Society of Canada. 71: 298. Bibcode: 1977JRASC..71..298W.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 21m 23.9561s [1] |
| Declination | +31° 22′ 02.573″ [1] |
| Apparent magnitude (V) | 5.3 – 13.6 [2] |
| Characteristics | |
| Spectral type | M7e [3] |
| U−B color index | 0.36 [1] |
| B−V color index | 1.71 [1] |
| Variable type | Mira [2] |
| Astrometry | |
| Radial velocity (Rv) | -5.12 [4] km/s |
| Proper motion (μ) |
RA: -7.73
[1]
mas/
yr Dec.: -13.03 [1] mas/ yr |
| Parallax (π) | 2.39 ± 0.17 mas [5] |
| Distance | 418+21 −18 [5] pc |
| Absolute magnitude (MV) | -0.8±0.3 [6] |
| Details | |
| Mass | 1.34 [7] M☉ |
| Radius | 308 [7] (537–664) [8] R☉ |
| Luminosity | 5,897 [9] L☉ |
| Temperature | 2,864 [7] (2,350–2,600) [8] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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. [10]
Variability
S Coronae Borealis was discovered to vary in brightness by German amateur astronomer Karl Ludwig Hencke in 1860. [11] It was classified as a long period variable star as other similar objects were discovered, [12] and later as a Mira variable. [2] 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. [13]
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, [8] although a more modern calculation gives a temperature of 2,864 K. [7] Similarly a calculation of the varying radius gives 537 to 664 R☉ [8] although a modern calculation of the radius gives 308 R☉. [7] The bolometric luminosity varies much less than the visual magnitude and is estimated to be 5,623 L☉. [7] 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. [5]
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. [7]
References
- ^ a b c d e f 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.
- ^ a b c VSX (4 January 2010). "S Coronae Borealis". AAVSO Website. American Association of Variable Star Observers. Retrieved 27 June 2014.
- ^ 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.
- ^ 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.
- ^ a b c 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.
- ^ Feijth, H. (1977). "The variable S Coronae Borealis". Zenit. 4: 451. Bibcode: 1977Zenit...4..451F.
- ^ a b c d e f g 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.
- ^ a b c d Wallerstein, G. (1977). "Are long-period variables really pulsating". Journal of the Royal Astronomical Society of Canada. 71: 298. Bibcode: 1977JRASC..71..298W.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.