V3903 Sagittarii

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V3903 Sagittarii
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 15h 15m 11.35199s[1]
Declination +04° 56′ 21.7099″[1]
Apparent magnitude (V) 7.00 - 7.45[2]
Spectral type O7V(n)z + B0:V:[3]
U−B color index −0.82[4]
B−V color index +0.16[4]
Variable type Algol[5]
Proper motion (μ) RA: +0.87 ± 0.67[1] mas/yr
Dec.: −0.66 ± 0.42[1] mas/yr
Parallax (π)2.18 ± 0.67[1] mas
Distance1,497[5] pc
Absolute magnitude (MV)−4.59 + −3.69[5]
Period (P)1.744204 days
Eccentricity (e)0
Inclination (i)65.20°
Semi-amplitude (K1)
236.6 km/s
Semi-amplitude (K2)
339.4 km/s
Mass27.27 M
Radius8.088 R
Luminosity122,000 L
Surface gravity (log g)4.058 cgs
Temperature38,000 K
Rotational velocity (v sin i)230 km/s
Mass19.01 M
Radius6.125 R
Luminosity45,500 L
Surface gravity (log g)4.143 cgs
Temperature34,100 K
Rotational velocity (v sin i)170 km/s
Age1.6 Myr
Other designations
V3903 Sgr, CD−24° 13962, HD 165921, HIP 88943, SAO 186366
Database references

V3903 Sagittarii is an eclipsing binary star system in the constellation Sagittiarus.


John Flamsteed gave this star the Flamsteed designation 11 Sagittarii, although for some reason this designation is now more often used to refer to the star he designated 1 Sagittarii.[6]


The system consists of two hot main-sequence stars. The spectral types have historically been accepted as O7V and O9V,[7] but the more recent Galactic O-Star Spectroscopic Survey gives a spectral type of O7V(n)z + B0:V:.[3] The system is one of the youngest known eclipsing binaries, and one of the few containing such massive stars that have not yet filled their roche lobes. Their likely age is around 1.6 million years, and they have current masses of 27 M and 19 M.[5]

V3903 Sagittarii varies in brightness. The General Catalogue of Variable Stars lists it as a possible hot irregular Orion variable star, but it has been shown to be a detached eclipsing binary system. The two stars are detached, that is they do not fill their roche lobes, which makes it an Algol-type eclipsing variable. The period is one day, 18 hours, 52 minutes.[7][5]

The distance derived from the annual parallax measured by the Hipparcos satellite is around 459 parsecs (1,500 ly),[1] but the distance calculated from the physical properties of the two stars is 1,500 pc.[5]


  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ 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. 
  3. ^ a b Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J. (2014). "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars". The Astrophysical Journal Supplement. 211: 10. arXiv:1312.6222Freely accessible. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. 
  4. ^ a b Schild, R. E.; Garrison, R. F.; Hiltner, W. A. (1983). "UBV photometry for southern OB stars". Astrophysical Journal Supplement Series. 51: 321. Bibcode:1983ApJS...51..321S. doi:10.1086/190852. 
  5. ^ a b c d e f g h Vaz, L. P. R.; Cunha, N. C. S.; Vieira, E. F.; Myrrha, M. L. M. (1997). "V 3903 Sagittarii: A massive main-sequence (O7V+O9V) detached eclipsing binary". Astronomy and Astrophysics. 327: 1094. Bibcode:1997A&A...327.1094V. 
  6. ^ Wagman, M. (1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy. 18 (3): 209. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305. 
  7. ^ a b Weidner, C. (2010). "The masses, and the mass discrepancy of O-type stars". Astronomy & Astrophysics. 524: A98. arXiv:1010.2204Freely accessible. Bibcode:2010A&A...524A..98W. doi:10.1051/0004-6361/201014491.