 A light curve for SU Cygni, plotted from TESS data | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19 44 48.734 |
| Declination | 29° 15′ 52.90″ |
| Apparent magnitude (V) | 6.44 to 7.22 |
| Characteristics | |
| Spectral type | F2Iab: + B8.0V + A0V: |
| Variable type | δ Cep |
| Astrometry | |
| Radial velocity (Rv) | −21.5±2.4 km/s |
| Proper motion (μ) | RA: 0.107 mas/yr Dec.: −3.247 mas/yr |
| Parallax (π) | 1.080 ± 0.006 mas |
| Distance | 3,021 ± 16 ly (926.3±5.0 pc) |
| Orbit | |
| Primary | SU Cyg A |
| Companion | SU Cyg B |
| Period (P) | 549.077±0.013 d |
| Semi-major axis (a) | 2.827±0.009 |
| Eccentricity (e) | 0.339±0.002 |
| Inclination (i) | 81.28±0.27° |
| Longitude of the node (Ω) | 266.24±0.24° |
| Periastron epoch (T) | 2,443,765.94±0.63 HJD |
| Argument of periastron (ω) (secondary) | 223.18±2.12° |
| Semi-amplitude (K1) (primary) | 30.25±0.05 km/s |
| Semi-amplitude (K2) (secondary) | 28.59±0.15 km/s |
| Orbit | |
| Primary | SU Cyg Ba |
| Companion | SU Cyg Bb |
| Period (P) | 4.67529(1) d |
| Semi-major axis (a) | ≥0.0287±0.0001 |
| Periastron epoch (T) | 2,456,977.994±0.003 HJD |
| Semi-amplitude (K1) (primary) | 66.89±0.21 km/s |
| Details | |
| Aa | |
| Mass | 4.859±0.058 M☉ |
| Radius | 31.9±6.0 R☉ |
| Luminosity | 1,349 L☉ |
| Surface gravity (log g) | 2.1–2.4 cgs |
| Temperature | 5,956 to 6,314 K |
| Metallicity | −0.03±0.04 dex |
| Ba | |
| Mass | 3.595±0.033 M☉ |
| Bb | |
| Mass | 1.546±0.009 M☉ |
| Other designations | |
| SU Cyg, BD+28°3460, GC 27336, HD 186688, HIP 97150, HR 7518, SAO 87659, PPM 109630, WDS J19448+2916Aa,Ab | |
| Database references | |
| SIMBAD | data |
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. The distance to this system is approximately 3,000 light years based on parallax measurements, and is the most accurate distance among Cepheids. It is a member of the Turner 9 open cluster of stars.
The variable luminosity of this star was announced by G. Müller and G. Kempf in 1898. The following year, M. Luizet determined a period of 3.846 days. 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. 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.
A companion star, designated component B, was detected photometrically by B. F. Madore in 1977, 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. 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. In 1998, the B-type companion was found to be a chemically peculiar HgMn star.
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.
References
- MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 6 January 2023.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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
- ^ 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.
- ^ 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.