S Muscae

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S Muscae
Musca constellation map.svg
Red circle.svg

Location of S Muscae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Musca
Right ascension 12h 12m 47.01834s[1]
Declination −70° 09′ 06.4363″[1]
Apparent magnitude (V) 6.394[2] (5.89 - 6.49[3])
Spectral type F6Ib (F6-G0[3]) + B5V[4]
U−B color index +0.66[5]
B−V color index +1.00[5]
Variable type δ Cepheid[3]
Radial velocity (Rv) −1.91[6] km/s
Proper motion (μ) RA: −7.79[1] mas/yr
Dec.: −0.60[1] mas/yr
Parallax (π) 1.99 ± 0.84[1] mas
Distance 863[2] pc
Absolute magnitude (MV) −4.01[7]
Period (P) 504.9 ± 0.07
Semi-major axis (a) 794 AU
Eccentricity (e) 0.08 ± 0.002
Inclination (i) 32 ± 1°
Semi-amplitude (K1)
14.7 ± 0.2 km/s
Mass 6.2[7] M
Radius 65.1[2] R
Luminosity 3,467[7] L
Metallicity +0.18[9]
Mass 5.3[7] M
Temperature 17,000[10] K
Other designations
S Mus, HR 4645, SAO 251791, CD−69°977, GSC 09231-00752, HD 106111, GC 16679, HIP 59551, AAVSO 1207-69
Database references

S Muscae is a classical (δ) Cepheid variable star in the constellation Musca about 2,600 light years away.

S Muscae is a yellow supergiant ranging between spectral types F6Ib and G0Ib and magnitudes 5.89 to 6.49 over a period of 9.66 days.[3] It is a luminous star around six times as massive as the Sun and 65.1 times the radius of the Sun. It is a binary star with a blue-white main sequence star companion likely to be of spectral type B3V to B5V with a mass of just over five solar masses,[11] one of the hottest and brightest companions of a Cepheid known. The two stars orbit each other every 505 days.[12]

S Muscae has been found to lie within the faint star cluster ASCC 69.[13]


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Moskalik, P.; Gorynya, N. A. (2005). "Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids". Acta Astronomica. 55: 247. Bibcode:2005AcA....55..247M. arXiv:astro-ph/0507076Freely accessible. 
  3. ^ a b c d 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. Bibcode:2009yCat....102025S. 
  4. ^ Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2014)". VizieR On-line Data Catalog: B/mk. Originally published in: Lowell Observatory (October 2014). 1. Bibcode:2014yCat....1.2023S. 
  5. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D. 
  6. ^ Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; Levato, H.; Morrell, N. I.; Torres, G.; Udry, S. (2004). "SB9: The ninth catalogue of spectroscopic binary orbits". Astronomy and Astrophysics. 424 (2): 727. Bibcode:2004A&A...424..727P. arXiv:astro-ph/0406573Freely accessible. doi:10.1051/0004-6361:20041213. 
  7. ^ a b c d e Remage Evans, Nancy; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; Karovska, Margarita; Tingle, Evan (2013). "Binary Cepheids: Separations and Mass Ratios in 5 M ⊙ Binaries". The Astronomical Journal. 146 (4): 93. Bibcode:2013AJ....146...93R. arXiv:1307.7123Freely accessible. doi:10.1088/0004-6256/146/4/93. 
  8. ^ Petterson, O. K. L.; Cottrell, P. L.; Albrow, M. D. (2004). "The orbits of southern binary Cepheids". Monthly Notices of the Royal Astronomical Society. 350: 95. Bibcode:2004MNRAS.350...95P. doi:10.1111/j.1365-2966.2004.07555.x. 
  9. ^ Klagyivik, P.; Szabados, L. (2009). "Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes". Astronomy and Astrophysics. 504 (3): 959. Bibcode:2009A&A...504..959K. arXiv:0908.3561Freely accessible. doi:10.1051/0004-6361/200811464. 
  10. ^ Evans, Nancy Remage; Massa, Derck; Fullerton, Alexander; Sonneborn, George; Iping, Rosina (2006). "Cepheid Masses: FUSE Observations of S Muscae". The Astrophysical Journal. 647 (2): 1387. Bibcode:2006ApJ...647.1387E. arXiv:astro-ph/0607489Freely accessible. doi:10.1086/505519. 
  11. ^ Bohm‐Vitense, Erika; Remage Evans, Nancy; Carpenter, Kenneth; Beck‐Winchatz, Bernhard; et al. (1997). "The Mass of the Classical Cepheid S Muscae". The Astrophysical Journal. 477 (2): 916. Bibcode:1997ApJ...477..916B. doi:10.1086/303725. 
  12. ^ Evans, Nancy Remage (1990). "The orbit and colors of the Cepheid S MUSCAE". Publications of the Astronomical Society of the Pacific. 102: 551. Bibcode:1990PASP..102..551E. doi:10.1086/132668. 
  13. ^ Remage Evans, Nancy; Pillitteri, Ignazio; Wolk, Scott; Guinan, Edward; Engle, Scott; Bond, Howard E.; Schaefer, Gail H.; Karovska, Margarita; Depasquale, Joseph; Tingle, Evan (2014). "X-Ray Detection of the Cluster Containing the Cepheid S Mus". The Astrophysical Journal Letters. 785 (2): L25. Bibcode:2014ApJ...785L..25R. arXiv:1403.6939Freely accessible. doi:10.1088/2041-8205/785/2/L25.