WY Geminorum is a binary star system in the northern constellation of Gemini, abbreviated WY Gem. It has an apparent visual magnitude that ranges from 7.26 down to 7.51,[4] which is too faint to be readily viewed with the naked eye. This system is located at a distance of approximately 6,300 light years from the Sun based on parallax measurements, and is receding with a radial velocity of 19.5 km/s.[7]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Gemini[2] |
| Right ascension | 06h 11m 56.250s[3] |
| Declination | +23° 12′ 25.41″[3] |
| Apparent magnitude (V) | 7.263 to 7.513[4] |
| Characteristics | |
| Spectral type | M2Ia-b + B2V[5] |
| B−V color index | 1.517±0.017[2] |
| Variable type | Irregular variable + eclipsing binary[6] |
| Astrometry | |
| Radial velocity (Rv) | 19.52±0.22[7] km/s |
| Proper motion (μ) | RA: 0.450 mas/yr[3] Dec.: −2.380 mas/yr[3] |
| Parallax (π) | 0.5169 ± 0.0343 mas[3] |
| Distance | 6,300 ± 400 ly (1,900 ± 100 pc) |
| Orbit[5] | |
| Period (P) | 64.48 ± 0.68 yr |
| Semi-major axis (a) | ≥ (4.09±0.19)×109 km |
| Eccentricity (e) | 0.61±0.03 |
| Periastron epoch (T) | 2,445,620±130 JD |
| Argument of periastron (ω) (secondary) | 57.5±4.5° |
| Semi-amplitude (K1) (primary) | 16.0±0.9 km/s |
| Details | |
| Primary | |
| Radius | 522+45 −34[8] R☉ |
| Surface gravity (log g) | 0.70[9] cgs |
| Temperature | 3,789[9] K |
| Metallicity [Fe/H] | −0.36[9] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
In 1922, M. L. Humason found the spectrum of HD 42474 matches an M-type star, but with the peculiarity of numerous bright lines. It appears similar to the spectrum of VV Cephei (HR 8383), an eclipsing binary.[11] P. Swings and O. Struve in 1941 discovered emission lines in the ultraviolet spectrum.[12] The presence of a B-type stellar spectrum from a companion star was confirmed by W. P. Bidelman in 1954. The primary spectrum matches an M-type supergiant star.[13] A. Cowley in 1970 found evidence of an atmospheric eclipse of the companion.[14] In 1981, A. Buzzoni determined the primary to be a semi-regular variable of the SRb type with a period of 169 days.[15]
This is a double-lined spectroscopic binary star system with an approximate orbital period of 64.48 ± 0.68 years and a high eccentricity (ovalness) of 0.61. The primary component is an M-type supergiant star with a stellar classification of M2Ia or b. The companion is most likely a hotter B-type main-sequence star with a class of B2V.[5] The pair are classified as a VV Cephei-type star system. The companion may be accreting matter from the supergiant around the time of periastron passage, resulting in the formation of an intermittent accretion disk orbiting the hotter star.[5] Radio emission has been detected, which is most likely coming from an ionized region in the stellar wind of the supergiant.[16]
References
edit- ^ "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 21 June 2024.
- ^ a b 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.
- ^ a b c d 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.
- ^ a b Laur, Jaan; et al. (February 2017), "Variability survey of brightest stars in selected OB associations", Astronomy & Astrophysics, 598: 27, arXiv:1611.02452, Bibcode:2017A&A...598A.108L, doi:10.1051/0004-6361/201629395, S2CID 119076598, A108.
- ^ a b c d Leedjaerv, Laurits (October 1998), "A spectroscopic study of the long-period binary star WY Geminorum", Astronomy and Astrophysics, 338: 139–150, Bibcode:1998A&A...338..139L.
- ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 255195566.
- ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ Ryan Norris. "Student Science at NMT: Learning Optical Interferometry Through Projects on Evolved Stars" (PDF). CHARA.
- ^ a b c Cenarro, A. J.; et al. (January 2007), "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters", Monthly Notices of the Royal Astronomical Society, 374 (2): 664–690, arXiv:astro-ph/0611618, Bibcode:2007MNRAS.374..664C, doi:10.1111/j.1365-2966.2006.11196.x, S2CID 119428437.
- ^ "WY Gem", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2024-02-09.
- ^ Humason, M. L. (April 1922), "An M-Type Star Whose Spectrum Contains Bright Lines", Publications of the Astronomical Society of the Pacific, 34 (198): 133, Bibcode:1922PASP...34..133H, doi:10.1086/123170, S2CID 119888135.
- ^ Swings, P.; Struve, O. (May 1941), "The Emission Lines in the Spectra of B 1985 and WY Geminorum", Astrophysical Journal, 93: 455, Bibcode:1941ApJ....93..455S, doi:10.1086/144287.
- ^ Martini, A. (1969), "The spectrum of W Y Gem in the years 1967-68", Memorie della Società Astronomia Italiana, 40: 25, Bibcode:1969MmSAI..40...25M.
- ^ Cowley, Anne (April 1970), "WY Geminorum-An Eclipsing System?", Publications of the Astronomical Society of the Pacific, 82 (485): 329, Bibcode:1970PASP...82..329C, doi:10.1086/128912.
- ^ Buzzoni, A. (November 1981), "WY Gem: a new semi-regular variable with a period of 169 days", GEOS Circular on Semi-Regular Variables, SR 2, Bibcode:1981GEOCS...2.....B.
- ^ Hjellming, R. M. (July 1985), Hjellming, Robert M.; Gobson, David M. (eds.), "The Radio Emission of VV Cephei-type Binaries", Radio Stars, Astrophysics and Space Science Library, 116: 151, Bibcode:1985ASSL..116..151H, doi:10.1007/978-94-009-5420-5_23, ISBN 90-277-2063-0.