Epoch J2000 Equinox J2000
|Right ascension||07h 29m 13.83049s|
|Declination||–43° 18′ 05.1597″|
|Apparent magnitude (V)||3.25|
|Spectral type||K5 III|
|U−B color index||+1.77|
|B−V color index||+1.52|
|Radial velocity (Rv)||+87.7 km/s|
|Proper motion (μ)||RA: –59.55 mas/yr
Dec.: +188.31 mas/yr
|Parallax (π)||16.84 ± 0.15 mas|
|Distance||194 ± 2 ly
(59.4 ± 0.5 pc)
|Period (P)||257.8 days|
|Periastron epoch (T)||20418.6|
|Argument of periastron (ω)
|σ Pup A|
|Rotational velocity (v sin i)||3.0 km/s|
Sigma Puppis (Sigma Pup, σ Puppis, σ Pup) is a binary star system in the southern constellation of Puppis. It has an apparent visual magnitude of 3.25, which is bright enough to be visible to the naked eye at night from the southern hemisphere. Through a telescope, it appears as an bright, orange-hued star with a nearby white companion. Parallax measurements indicate this star is located at a distance of about 194 light-years (59 parsecs) from Earth.
This is a spectroscopic binary system, consisting of an orbiting pair of stars that have not been individually resolved with a telescope. Their orbital period is 257.8 days and the eccentricity is 0.17. The pair form an eclipsing binary of the Beta Lyrae type and a period of 130.5 days, or one half of their orbital period. The eclipse of the primary component causes a decline of 0.04 magnitudes, while the secondary eclipse reduces the magnitude by 0.03.
The combined stellar classification is K5 III, which matches the spectrum of a giant star. The measured angular diameter of the primary star is 16.71 ± 2.84 mas. At the estimated distance of this system, this yields a physical size of about 107 times the radius of the Sun. The primary component shows the behavior of a slow irregular variable.
In addition to its binary components, Sigma Puppis has a more distant companion that has a matching proper motion, suggesting that it may be gravitationally bound to the binary. This magnitude 8.5 star is at an angular separation of 22.4 arcseconds with a position angle of 74° from Sigma Puppis, which is equivalent to a projected separation of 1,200 Astronomical Units. In 1970, American astronomer Olin J. Eggen suggested that Sigma Puppis belonged to a moving group of stars that share a similar motion through space, and thereby a common origin. It served as the eponym for this, the σ Puppis group. The existence of this group was later brought into question.
- van Leeuwen, F. (November 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
- Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J
- Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, Ann Arbor: Dept. of Astronomy, University of Michigan: distributed by University Microfilms International, Bibcode:1978mcts.book.....H
- Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E
- Batten, A. H.; Fletcher, J. M.; Mann, P. J. (1978), "Seventh catalogue of the orbital elements of spectroscopic binary systems.", Publications of the Dominion Astrophysical Observatory Victoria 15: 121–295, Bibcode:1978PDAO...15..121B See pp. 150–151.
- Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
- Costa, J. M. et al. (February 2002), "The tidal effects on the lithium abundance of binary systems with giant component", Astronomy and Astrophysics 382: 1016–1020, arXiv:astro-ph/0111539, Bibcode:2002A&A...382.1016C, doi:10.1051/0004-6361:20011676
- "sig Pup -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2010-01-05
- Plotner, Tammy; Mann, Terry (2007), The Night Sky Companion: A Yearly Guide to Sky-Watching, Patrick Moore's Practical Astronomy Series, Springer, p. 156, ISBN 0-387-71608-4, retrieved 2012-01-11
- Otero, Sebastián A. (October 2007), "New Elements for 54 Eclipsing Binaries", Open European Journal on Variable Stars 72 (1): 1–19, Bibcode:2007OEJV...72....1O
- Samus, N. N.; Durlevich, O. V. (February 12, 2009), GCVS Variability Types and Distribution Statistics of Designated Variable Stars According to their Types of Variability, Sternberg Astronomical Institute, Moscow University, retrieved 2012-04-18
- Richichi; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
- Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science 3 (2nd ed.), Courier Dover Publications, p. 150, ISBN 0-486-23673-0, retrieved 2012-01-11
- Eggen, O. J. (June 1971), "The ζ Herculis, σ Puppis, ∈ Indi, and η Cephei Groups of Old Disk Population Stars", Publications of the Astronomical Society of the Pacific 83 (493): 251, Bibcode:1971PASP...83..251E, doi:10.1086/129119
- Taylor, B. J. (October 2000), "A statistical analysis of the metallicities of nine old superclusters and moving groups", Astronomy and Astrophysics 362: 563–579, Bibcode:2000A&A...362..563T