Astronomy:SU Cygni
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 44m 48.734s[2] |
| Declination | 29° 15′ 52.90″[2] |
| Apparent magnitude (V) | 6.44 to 7.22[3] |
| Characteristics | |
| Spectral type | F2Iab: + B8.0V + A0V:[4][5] |
| Variable type | δ Cep[3] |
| Astrometry | |
| Radial velocity (Rv) | −21.5±2.4[6] km/s |
| Proper motion (μ) | RA: 0.107[2] mas/yr Dec.: −3.247[2] mas/yr |
| Parallax (π) | 1.0275 ± 0.0522[2] mas |
| Distance | 3,200 ± 200 ly (970 ± 50 pc) |
| Orbit[7] | |
| Primary | SU Cyg A |
| Companion | SU Cyg B |
| Period (P) | 549.24±0.02 d |
| Eccentricity (e) | 0.350+0.004−0.003 |
| Periastron epoch (T) | 2,443,766.2±1.1 HJD |
| Argument of periastron (ω) (secondary) | 223.85±0.85° |
| Semi-amplitude (K1) (primary) | 29.83±0.15 km/s |
| Details | |
| Primary | |
| Mass | 4.7[4] M☉ |
| Radius | 43.9[8] R☉ |
| Luminosity | 1,349[4] L☉ |
| Surface gravity (log g) | 2.1–2.4[9] cgs |
| Temperature | 5,956 to 6,314[9] K |
| Metallicity [Fe/H] | −0.03±0.04[7] dex |
| Secondary | |
| Mass | 4.7±0.7[10] M☉ |
| Other designations | |
| 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 3.8455473 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 3,200 light years based on parallax measurements.[2] It is a member of the Turner 9 open cluster of stars.[10]
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.[8] 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.[17] In 1998, the B-type companion was found to be a chemically peculiar HgMn star.[18]
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.[10]
References
- ↑ MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html, retrieved 6 January 2023.
- ↑ 2.0 2.1 2.2 2.3 2.4 Brown, A. G. A. (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics 649: A1. doi:10.1051/0004-6361/202039657. Bibcode: 2021A&A...649A...1G. Gaia EDR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S.
- ↑ 4.0 4.1 4.2 Evans, Nancy Remage et al. (October 2013), "Binary Cepheids: Separations and Mass Ratios in 5 M⊙ Binaries", The Astronomical Journal 146 (4): 93, doi:10.1088/0004-6256/146/4/93, 93, Bibcode: 2013AJ....146...93E.
- ↑ 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, doi:10.1093/mnras/stx598, Bibcode: 2017MNRAS.468.3533E.
- ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35493 Hipparcos Stars", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G.
- ↑ 7.0 7.1 Groenewegen, M. A. T. (2008), "Baade-Wesselink distances and the effect of metallicity in classical cepheids", Astronomy and Astrophysics 488 (1): 25–35, doi:10.1051/0004-6361:200809859, Bibcode: 2008A&A...488...25G.
- ↑ 8.0 8.1 Imbert, M. (December 1984), "Determination de rayons de cepheides. III. Vitesses radiales, orbite spectroscopique et dimension de SU Cyg" (in Fr), Astronomy and Astrophysics Supplement Series 58: 529–536, Bibcode: 1984A&AS...58..529I.
- ↑ 9.0 9.1 Andrievsky, S. M. et al. (2013), "Barium abundances in Cepheids", Monthly Notices of the Royal Astronomical Society 428 (4): 3252, doi:10.1093/mnras/sts270, Bibcode: 2013MNRAS.428.3252A.
- ↑ 10.0 10.1 10.2 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, doi:10.1051/0004-6361/201834211, A117, Bibcode: 2019A&A...623A.117K.
- ↑ "SU Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=SU+Cyg.
- ↑ Müller, G.; Kempf, P. (March 1898), "Zwei neue Veränderliche von kurzer Periode" (in De), Astronomische Nachrichten 146 (3): 37, doi:10.1002/asna.18981460303, Bibcode: 1898AN....146...37M, https://zenodo.org/record/1424765. Note: listed as BD. +28°3460.
- ↑ Luizet, Michel (May 1899), "Sur les deux nouvelles étoiles variables U Petit Renard et SU Cygne" (in Fr), Astronomische Nachrichten 149 (18): 313, doi:10.1002/asna.18991491804, Bibcode: 1899AN....149..313L.
- ↑ 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, doi:10.1086/121692, Bibcode: 1906PASP...18..252M.
- ↑ Shapley, H. (1916), "The variations in spectral type of twenty Cepheid variables", Astrophysical Journal 44: 273, doi:10.1086/142295, Bibcode: 1916ApJ....44..273S.
- ↑ 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, doi:10.1093/mnras/178.3.505, Bibcode: 1977MNRAS.178..505M.
- ↑ 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, doi:10.1086/118422, Bibcode: 1997AJ....113.2104T.
- Evans, Nancy Remage; Bolton, C. T. (June 1990), "The Mass of the Classical Cepheid SU Cygni", Astrophysical Journal 356: 630, doi:10.1086/168869, Bibcode: 1990ApJ...356..630E.
- Evans, Nancy R. (March 1988), "The Orbit of the Classical Cepheid SU Cygni", Astrophysical Journal Supplement 66: 343, doi:10.1086/191260, Bibcode: 1988ApJS...66..343E.
- 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 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, doi:10.1086/130443, Bibcode: 1979PASP...91...67F.
- Schneider, M. (1967), "Étude spectrophotométrique de Céphéide SU Cyg" (in Fr), Journal des Observateurs 50: 419, Bibcode: 1967JO.....50..419S.
- Hellerich, J. (November 1919), "Ableitung Spektroskopischer Bahnelemente für S Sagittae und SU Cygni" (in De), Astronomische Nachrichten 210 (5): 65, doi:10.1002/asna.19202100502, Bibcode: 1919AN....210...65H.
- Pickering, Edward C. (April 1899), "Notes on variable stars", Astronomische Nachrichten 149 (9): 171, doi:10.1002/asna.18991490905, Bibcode: 1899AN....149..171P, https://zenodo.org/record/1918893.
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