Sigma Puppis

Sigma Puppis, Latinized from σ Puppis, is a binary star system in the southern constellation Puppis. It has an apparent visual magnitude of 3.25,^[2] which is bright enough to be visible to the naked eye at night from the Southern Hemisphere. Through a telescope, it appears as a bright, orange-hued star with a nearby white companion.^[10] Parallax measurements indicate this star is located at a distance of about 192 light-years (59 parsecs) from Earth.^[1]

A light curve for Sigma Puppis, adapted from Otero (2007)^[11]

Sigma Puppis

Location of σ Puppis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Puppis
Right ascension	07h 29m 13.83263s[1]
Declination	−43° 18′ 05.1674″[1]
Apparent magnitude (V)	3.25[2]
Characteristics
Spectral type	K5 III[3]
U−B color index	+1.77[2]
B−V color index	+1.52[2]
Astrometry
Radial velocity (Rv)	+87.3[4] km/s
Proper motion (μ)	RA: +199.39 mas/yr[1] Dec.: −61.828 mas/yr[1]
Parallax (π)	17.0234 ± 0.5614 mas[1]
Distance	192 ± 6 ly (59 ± 2 pc)
Absolute magnitude (MV)	−0.50[5]
Orbit[6]
Period (P)	257.8 days
Eccentricity (e)	0.17
Periastron epoch (T)	20418.6
Argument of periastron (ω) (secondary)	349.3°
Semi-amplitude (K1) (primary)	18.6 km/s
Details
σ Pup A
Mass	1.65[7] M☉
Radius	43.7[4] R☉
Luminosity	344[7] L☉
Surface gravity (log g)	1.51[7] cgs
Temperature	4,077±4[7] K
Rotational velocity (v sin i)	3.0[8] km/s
Other designations
σ Pup, Sigma Pup, CPD−43  1499, FK5 1194, GC 10040, HD 59717, HIP 36377, HR 2878, SAO 218755, WDS J07292-4318A[9]
Database references
SIMBAD	data

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 primary is 44 times larger than the Sun^[4] and 340 times more luminous. Its surface has an effective temperature of 4,077 K,^[7] giving it the orange hue of a K-type star.^[13] It 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 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]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
3. 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
4. Wood, Brian E.; Müller, Hans-Reinhard; Harper, Graham M. (2016-09-23), "Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars", The Astrophysical Journal, 829 (2): 74, arXiv:1607.07732, Bibcode:2016ApJ...829...74W, doi:10.3847/0004-637X/829/2/74, ISSN 0004-637X
5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
6. 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, 150–151, Bibcode:1978PDAO...15..121B
7. Ayres, Thomas (2023-05-01). "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022". The Astrophysical Journal Supplement Series. 266 (1): 6. Bibcode:2023ApJS..266....6A. doi:10.3847/1538-4365/acb535. ISSN 0067-0049. Sigma Puppis' database entry at VizieR.
8. Costa, J. M.; et al. (February 2002), "The tidal effects on the lithium abundance of binary systems with giant component", Astronomy and Astrophysics, 382 (3): 1016–1020, arXiv:astro-ph/0111539, Bibcode:2002A&A...382.1016C, doi:10.1051/0004-6361:20011676, S2CID 17024265
9. "sig Pup -- Spectroscopic binary", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2010-01-05
10. 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 978-0-387-71608-4, retrieved 2012-01-11
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
12. 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
13. "The Colour of Stars". Australia National Telescope Facility. Retrieved 2024-05-27.
14. Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the solar system, Dover books explaining science, vol. 3 (2nd ed.), Courier Dover Publications, p. 150, ISBN 0-486-23673-0, retrieved 2012-01-11
15. 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
16. 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