SU Cygni is a triple star system in the northern constellation of Cygnus, abbreviated SU Cyg. The primary component of the system is a classical Cepheid variable with a period of 3.84559 days. The changing luminosity of this star causes the system to vary in brightness from a peak apparent visual magnitude of 6.44 down to magnitude 7.22 over the course of its cycle.[3] The distance to this system is approximately 3,000 light years based on parallax measurements, and is the most accurate distance among Cepheids.[7] It is a member of the Turner 9 open cluster of stars.[11]
The variable luminosity of this star was announced by G. Müller and G. Kempf in 1898.[12] The following year, M. Luizet determined a period of 3.846 days.[13] In 1906, the radial velocity of this star was found to be variable by J. D. Maddrill, with its cycle matching the luminosity period but trailing in phase by half a day.[14] By 1916 it was classified as a Cepheid variable, with spectrographic studies showing that the spectral type varied over the course of each cycle. It ranged from a class of A6 near peak luminosity down to F7 at minimum.[15]
A companion star, designated component B, was detected photometrically by B. F. Madore in 1977,[16] with the colors suggesting a B-type main-sequence star with a class of B6–7V. This finding was supported by observations of J. D. Fernie in 1979, who determined a class of B6V. In 1984, M. Imbert measured an orbital period of 549.2 days for the pair, with an orbital eccentricity (ovalness) of 0.35.[17] Ultraviolet observations with the IUE spacecraft in 1985 showed that the companion is a close binary system with a period of 4.7 days. The members of this pair have classes of B8 and A0.[18] In 1998, the B-type companion was found to be a chemically peculiar HgMn star.[19]
There is a candidate comoving companion star located at an angular separation of 24″ to the west of SU Cyg. It is an A-type main-sequence star with a class of A2V. This star does not appear to be gravitationally bound to SU Cyg.[11]
References
- ^ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 6 January 2023.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ a b c Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
- ^ a b Evans, Nancy Remage; et al. (October 2013), "Binary Cepheids: Separations and Mass Ratios in 5 M⊙ Binaries", The Astronomical Journal, 146 (4): 93, arXiv:1307.7123, Bibcode:2013AJ....146...93E, doi:10.1088/0004-6256/146/4/93, S2CID 34133110, 93.
- ^ Eggleton, Peter P.; Yakut, Kadri (July 2017), "Models for 60 double-lined binaries containing giants", Monthly Notices of the Royal Astronomical Society, 468 (3): 3533–3556, arXiv:1611.05041, Bibcode:2017MNRAS.468.3533E, doi:10.1093/mnras/stx598.
- ^ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35493 Hipparcos Stars", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
- ^ a b c d e f Gallenne, A.; Evans, N. R.; Kervella, P.; Monnier, J. D.; Proffitt, C. R.; Schaefer, G. H.; Winston, E. M.; Kuraszkiewicz, J.; Mérand, A. (2024-11-15), Multiplicity of Galactic Cepheids from long-baseline interferometry V. High-accuracy orbital parallax and mass of SU Cygni, arXiv:2411.06647
- ^ a b Andrievsky, S. M.; et al. (2013), "Barium abundances in Cepheids", Monthly Notices of the Royal Astronomical Society, 428 (4): 3252, arXiv:1210.6211, Bibcode:2013MNRAS.428.3252A, doi:10.1093/mnras/sts270.
- ^ Groenewegen, M. A. T. (2008), "Baade-Wesselink distances and the effect of metallicity in classical cepheids", Astronomy and Astrophysics, 488 (1): 25–35, arXiv:0807.1269, Bibcode:2008A&A...488...25G, doi:10.1051/0004-6361:200809859, S2CID 13871801.
- ^ "SU Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-01-04.
- ^ a b Kervella, Pierre; et al. (March 2019), "Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2. II. Resolved common proper motion pairs", Astronomy & Astrophysics, 623: 40, arXiv:1908.00545, Bibcode:2019A&A...623A.117K, doi:10.1051/0004-6361/201834211, A117.
- ^ Müller, G.; Kempf, P. (March 1898), "Zwei neue Veränderliche von kurzer Periode", Astronomische Nachrichten (in German), 146 (3): 37, Bibcode:1898AN....146...37M, doi:10.1002/asna.18981460303. Note: listed as BD. +28°3460.
- ^ Luizet, Michel (May 1899), "Sur les deux nouvelles étoiles variables U Petit Renard et SU Cygne", Astronomische Nachrichten (in French), 149 (18): 313, Bibcode:1899AN....149..313L, doi:10.1002/asna.18991491804.
- ^ Maddrill, J. D. (August 1906), "Note on the variable radial velocity and the period of SU Cygni", Publications of the Astronomical Society of the Pacific, 18 (109): 252–253, Bibcode:1906PASP...18..252M, doi:10.1086/121692, S2CID 119576552.
- ^ Shapley, H. (1916), "The variations in spectral type of twenty Cepheid variables", Astrophysical Journal, 44: 273, Bibcode:1916ApJ....44..273S, doi:10.1086/142295.
- ^ Madore, B. F. (March 1977), "The frequency of Cepheids with companions: a photoelectric approach", Monthly Notices of the Royal Astronomical Society, 178 (3): 505–511, Bibcode:1977MNRAS.178..505M, doi:10.1093/mnras/178.3.505.
- ^ Imbert, M. (December 1984), "Determination de rayons de cepheides. III. Vitesses radiales, orbite spectroscopique et dimension de SU Cyg", Astronomy and Astrophysics Supplement Series (in French), 58: 529–536, Bibcode:1984A&AS...58..529I.
- ^ Evans, N. R.; et al. (March 1985), "Ultraviolet Observations of the System Containing the Cepheid SU Cyg", Bulletin of the American Astronomical Society, 17: 559, Bibcode:1985BAAS...17..559E.
- ^ Wahlgren, G. M.; Evans, N. R. (April 1998), "A HgMn companion to the Cepheid SU Cyg", Astronomy and Astrophysics, 332: L33 – L36, Bibcode:1998A&A...332L..33W.
Further reading
- Turner, David G.; et al. (June 1998), "A Search for the Parent Cluster of the Cepheid SU Cygni", Journal of the Royal Astronomical Society of Canada, 92: 145, Bibcode:1998JRASC..92..145T.
- Turner, David G.; et al. (June 1997), "Galactic Clusters with Associated Cepheid Variables. V. The Case of SU Cygni", The Astronomical Journal, 113: 2104, Bibcode:1997AJ....113.2104T, doi:10.1086/118422.
- Evans, Nancy Remage; Bolton, C. T. (June 1990), "The Mass of the Classical Cepheid SU Cygni", Astrophysical Journal, 356: 630, Bibcode:1990ApJ...356..630E, doi:10.1086/168869.
- Evans, Nancy R. (March 1988), "The Orbit of the Classical Cepheid SU Cygni", Astrophysical Journal Supplement, 66: 343, Bibcode:1988ApJS...66..343E, doi:10.1086/191260.
- Remage Evans, N.; Arellano Ferro, A. (September 1986), "The luminosities of the binary cepheids SU Cyg, SU CAS and W Sgr", ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE, vol. 263, pp. 403–404, Bibcode:1986ESASP.263..403R.
- Fernie, J. D. (February 1979), "Photometry of the classical cepheid SU Cygni", Publications of the Astronomical Society of the Pacific, 91: 67–70, Bibcode:1979PASP...91...67F, doi:10.1086/130443, S2CID 120465293.
- Schneider, M. (1967), "Étude spectrophotométrique de Céphéide SU Cyg", Journal des Observateurs (in French), 50: 419, Bibcode:1967JO.....50..419S.
- Hellerich, J. (November 1919), "Ableitung Spektroskopischer Bahnelemente für S Sagittae und SU Cygni", Astronomische Nachrichten (in German), 210 (5): 65, Bibcode:1919AN....210...65H, doi:10.1002/asna.19202100502.
- Pickering, Edward C. (April 1899), "Notes on variable stars", Astronomische Nachrichten, 149 (9): 171, Bibcode:1899AN....149..171P, doi:10.1002/asna.18991490905.
