A light curve for Sigma Puppis, adapted from Otero (2007)[11]
This is a spectroscopic binary system,[9] 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.[6] 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 of a magnitude, while the secondary eclipse reduces the magnitude by 0.03.[11][12]
The combined stellar classification is K5 III,[3] which matches the spectrum of a giant star. The measured angular diameter of the primary star is 16.71 ± 2.84 mas.[13] At the estimated distance of this system, this yields a physical size of about 107 times the radius of the Sun.[7] The primary component shows the behavior of a slow irregular variable.[11][12]
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[10] 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 unit|AU.[14] 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.[15] The existence of this group was later brought into question.[16]
↑ 2.02.12.22.3Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory4 (99): 99, Bibcode: 1966CoLPL...4...99J
↑ 3.03.1Houk, 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; Heard, John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, 30, University of Toronto: International Astronomical Union, p. 57, Bibcode: 1967IAUS...30...57E
↑ 6.06.1Batten, 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 Victoria15: 121–295;150–151, Bibcode: 1978PDAO...15..121B
↑Costa, J. M. et al. (February 2002), "The tidal effects on the lithium abundance of binary systems with giant component", Astronomy and Astrophysics382 (3): 1016–1020, doi:10.1051/0004-6361:20011676, Bibcode: 2002A&A...382.1016C
↑ 11.011.111.2Otero, Sebastián A. (October 2007), "New Elements for 54 Eclipsing Binaries", Open European Journal on Variable Stars72 (1): 1–19, Bibcode: 2007OEJV...72....1O
↑Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics431 (2): 773–777, doi:10.1051/0004-6361:20042039, Bibcode: 2005A&A...431..773R
↑Taylor, B. J. (October 2000), "A statistical analysis of the metallicities of nine old superclusters and moving groups", Astronomy and Astrophysics362: 563–579, Bibcode: 2000A&A...362..563T