Double Cluster (north is left)
Epoch J2000 Equinox J2000
|Right ascension||2h 22m 51.70928s|
|Declination||58° 31′ 11.4476″|
|Apparent magnitude (V)||9.23 (7.9 - 12.0)|
|Spectral type||M4.5I (M3Iae - M7)|
|B−V color index||2.65|
|Radial velocity (Rv)||-39.71 km/s|
|Proper motion (μ)|| RA: −0.49 ± 0.23 mas/yr |
Dec.: −1.19 ± 0.20 mas/yr
|Parallax (π)||0.413 ± 0.017 mas|
|Distance||7,900 ± 300 ly |
(2,420 ± 100 pc)
|Absolute magnitude (MV)||−6.36 (at mV 9.23)|
|Radius||1,212 ± 124, 780 - 1,230 R☉|
|Luminosity||86,000 - 186,000 L☉|
|Surface gravity (log g)||0.0 cgs|
S Persei is a red supergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.
S Persei was named by German astronomer Adalbert Krueger in 1874 after observing that it varied in brightness. It was subsequently listed in major stellar catalogues of that era as HD 14528 and BD+57 552.
S Persei varies slowly by several magnitudes, a factor of over 40 in brightness. It has a main period of somewhat over two years, but shows significant unpredictability. There is a strong variation in the amplitude from around one magnitude to about four magnitudes, and these have been interpreted as beats due to a second period of about 940 days. Other analyses find only the primary period of 813 ± 60 days.
S Persei is classified as a semiregular variable star of type SRc, indicating that it is a supergiant, and it has one of the largest visual amplitudes of any variable of this type. While the General Catalogue of Variable Stars lists it as varying between magnitudes 7.9 and 12.0, it has since been seen fainter.
The spectral type of S Persei also varies. Typically it is a red supergiant of spectral class M3 or M4, but particularly at deep visual minima it may show a much cooler spectral type of M7 or M8, highly unusual for a supergiant.
Many of the visually bright variable stars belong to this class of semiregulars, as these stars are extremely large and luminous, and hence visible across long distances. S Persei has a radius of 780 times the sun's radius (R☉), but could be larger with a radius of 1,230 R☉. It has been described as a hypergiant. Its angular diameter has been measured directly and found to be somewhat elliptical. Modelled as a uniform disk, the radius corresponds to 1,212 ± 124 R☉.
The temperature has been calculated from the spectrum using a DUSTY model, giving an effective photospheric temperature of 3,600 K and a temperature of 900 K for the surrounding dust torus. This is consistent with previous studies, but the derived luminosity from different authors varies from 86,000 L☉ to 186,000 L☉. Older studies frequently calculated higher luminosities, lower temperatures, and consequently larger values for the radius.
The mass of S Persei is also uncertain, but expected to be around 20 M☉. Mass is being lost at ×10−6 M☉ per year, 6.8 leading to an extensive and complex circumstellar environment of gas and dust.
S Persei is surrounded by clouds containing water molecules which produce maser emission. This allows the distance to be measured very accurately using very long baseline interferometry, giving an annual parallax of 0.413 ± 0.017 milliarcseconds. For comparison the Gaia Data Release 2 parallax is ±0.1214 mas. 0.2217 It lies somewhat further away than the centres of the Double Cluster open clusters, but definitely within the Per OB1 association and the Perseus Arm of the galaxy.
- Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- Emily M. Levesque; Philip Massey; K. A. G. Olsen; Bertrand Plez; et al. (August 2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
- Samus', N. N.; Goranskii, V. P.; Durlevich, O. V.; Zharova, A. V.; Kazarovets, E. V.; Kireeva, N. N.; Pastukhova, E. N.; Williams, D. B.; Hazen, M. L. (2003). "An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates". Astronomy Letters. 29 (7): 468. Bibcode:2003AstL...29..468S. doi:10.1134/1.1589864.
- 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". Astronomy and Astrophysics. 430 (1): 165–186. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. ISSN 0004-6361.
- Asaki, Y.; Deguchi, S.; Imai, H.; Hachisuka, K.; Miyoshi, M.; Honma, M. (2010). "DISTANCE AND PROPER MOTION MEASUREMENT OF THE RED SUPERGIANT, S PERSEI, WITH VLBI H2O MASER ASTROMETRY". The Astrophysical Journal. 721 (1): 267–277. arXiv:1007.4874. Bibcode:2010ApJ...721..267A. doi:10.1088/0004-637X/721/1/267. ISSN 0004-637X.
- Yates, J. A.; Cohen, R. J. (1994). "Circumstellar Envelope Structure of Late Type Stars as Revealed by MERLIN Observations of 22-GHZ Water Masers". Monthly Notices of the Royal Astronomical Society. 270 (4): 958. Bibcode:1994MNRAS.270..958Y. doi:10.1093/mnras/270.4.958.
- Thompson, R. R.; Creech-Eakman, M. J. (2003). "Interferometric observations of the supergiant S Persei: Evidence for axial symmetry and the warm molecular layer". American Astronomical Society Meeting 203. 203: 49.07. Bibcode:2003AAS...203.4907T.
- Fok, Thomas K. T.; Nakashima, Jun-Ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji (2012). "Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters". The Astrophysical Journal. 760: 65. arXiv:1209.6427. Bibcode:2012ApJ...760...65F. doi:10.1088/0004-637X/760/1/65.
- Mauron, N.; Josselin, E. (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993.
- Verhoelst, T.; Van Der Zypen, N.; Hony, S.; Decin, L.; Cami, J.; Eriksson, K. (2009). "The dust condensation sequence in red supergiant stars". Astronomy and Astrophysics. 498: 127. arXiv:0901.1262. Bibcode:2009A&A...498..127V. doi:10.1051/0004-6361/20079063.
- Gonzalez, Guillermo; Wallerstein, George (2000). "Elemental Abundances in Evolved Supergiants. II. The Young Clusters H and χ Persei". The Astronomical Journal. 119 (4): 1839. Bibcode:2000AJ....119.1839G. doi:10.1086/301319.
- García-Hernández, D. A.; García-Lario, P.; Plez, B.; Manchado, A.; d'Antona, F.; Lub, J.; Habing, H. (2007). "Lithium and zirconium abundances in massive Galactic O-rich AGB stars". Astronomy and Astrophysics. 462 (2): 711. arXiv:astro-ph/0609106. Bibcode:2007A&A...462..711G. doi:10.1051/0004-6361:20065785.
- Krüger, A. (1874). "Anzeige eines neuen veränderlichen Sternes (S Persei)". Astronomische Nachrichten. 83 (10): 157. Bibcode:1874AN.....83..157K. doi:10.1002/asna.18740831005.
- Smith, Horace A. (1974). "S Persei a Semi-Regular Variable with Two Periods". Journal of the American Association of Variable Star Observers. 3: 20. Bibcode:1974JAVSO...3...20S.
- Kiss, L. L.; Szabó, Gy. M.; Bedding, T. R. (2006). "Variability in red supergiant stars: Pulsations, long secondary periods and convection noise". Monthly Notices of the Royal Astronomical Society. 372 (4): 1721. arXiv:astro-ph/0608438. Bibcode:2006MNRAS.372.1721K. doi:10.1111/j.1365-2966.2006.10973.x.
- Wing, R. F. (2009). "The Biggest Stars of All". The Biggest. 412: 113. Bibcode:2009ASPC..412..113W.
- Zhang, B.; Reid, M. J.; Menten, K. M.; Zheng, X. W.; Brunthaler, A. (2012). "The distance and size of the red hypergiant NML Cygni from VLBA and VLA astrometry". Astronomy & Astrophysics. 544: A42. arXiv:1207.1850. Bibcode:2012A&A...544A..42Z. doi:10.1051/0004-6361/201219587. ISSN 0004-6361.
- Ivezic, Zeljko; Nenkova, Maia; Elitzur, Moshe (1999). "User Manual for DUSTY". arXiv:astro-ph/9910475.
- De Jager, C.; Nieuwenhuijzen, H.; Van Der Hucht, K. A. (1988). "Mass loss rates in the Hertzsprung-Russell diagram". Astronomy and Astrophysics Supplement Series (ISSN 0365-0138). 72: 259. Bibcode:1988A&AS...72..259D.
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
- Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. de l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
- Skiff, B. A. (1994). "Photometry of Stars in the Field of S Persei". Information Bulletin on Variable Stars. 4054: 1. Bibcode:1994IBVS.4054....1S.