SW Lyncis

SW Lyncis is a binary or possibly a multiple-star system in the northern constellation of Lynx, abbreviated SW Lyn. With a combined apparent visual magnitude of 9.58,[3] it is too faint to be visible to the naked eye. The system is located at a distance of approximately 970 light years based on parallax measurements, and is drifting further away with a net radial velocity of about +32 km/s.[5]

SW Lyncis

A visual band light curve for SW Lyncis, adapted from Ogloza et al. (1998)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Lynx
Right ascension 08h 07m 41.569s[2]
Declination +41° 48′ 01.74″[2]
Apparent magnitude (V) 9.58[3]
primary eclipse: 10.20
secondary eclipse: 9.65[4]
Characteristics
Spectral type F2 V[5]
B−V color index 0.255±0.041[3]
Variable type Detached Algol[4]
Astrometry
Radial velocity (Rv)+32.39±1.35[5] km/s
Proper motion (μ) RA: −16.887 mas/yr[2]
Dec.: −36.795 mas/yr[2]
Parallax (π)3.3655 ± 0.0571 mas[2]
Distance970 ± 20 ly
(297 ± 5 pc)
Orbit[5]
Period (P)0.644066 d
Eccentricity (e)0.00
Periastron epoch (T)2,451,400.1795±0.0025 HJD
Semi-amplitude (K1)
(primary)		116.73±1.65 km/s
Semi-amplitude (K2)
(secondary)		222.75±3.20 km/s
Details[6]
Primary
Mass1.77±0.37 M☉
Radius1.76±0.16 R☉
Luminosity10.15±0.15 L☉
Temperature7,800 K
Secondary
Mass0.92±0.18 M☉
Radius1.32±0.12 R☉
Luminosity0.64±0.01 L☉
Temperature4,588±6 K
Other designations
SW Lyn, BD+42°1811, HD 67008, HIP 39771, SAO 42180[7]
Database references
SIMBADdata

The variable luminosity of this system was reported by R. Kippenhahn in 1955.[8] Huth in 1958 classified it as a β Lyr-type variable.[9] W. Strohmeier found a short period of 15.46 hours in 1959, although there was no minimum detected from a secondary eclipse. H. Mauder classified this as an eclipsing binary of the Algol type based on a light curve assembled in 1960. J. K. Gleim in 1967 noted that the period of the system had changed, suggesting that there may be a third body in the system. He considered it to be a member of the β Lyr class, although it is more closely related to the Algol type than W Ursae Majoris variables.[10]

M. Vetešník noted in 1968 that the light curve for the system appeared noticeably asymmetric.[9] He published orbital elements for this system in 1977 and found a stellar classification of F2V for the primary component. A low mass ratio suggested the secondary is much smaller and less luminous than the primary.[11] L. Qingyao and associates in 1991 concluded that this is a semi-detached system with one of the components filling its Roche lobe, and thought the secondary to be over-sized and over-luminous for its mass.[12] W. Ogłoza and associates in 1998 supported the idea of a semi-detached system, and found that the light curve suggested the presence of a third component in the system with an orbital period of 5.83 years.[1] The third component is thought to contribute less than 1.5% of the light output of the system.[13]

In 2010, C.-H. Kim and associates performed modelling of the 34-year cycle variations of the system and conjectured that two additional circumbinary companions are creating this effect. However, subsequent studies suggest that such a configuration would be too unstable. The system behavior remains unexplained.[14] SW Lyn is presently classified as a near contact binary that decreases in brightness to magnitude 10.20 during the primary eclipse and to magnitude 9.65 with the secondary eclipse.[15]

References
  1. Ogloza, W.; et al. (December 1998), "The analysis of photometric light curves and the third body in the eclipsing binary system SW Lyn", Astronomy and Astrophysics, 340: 81–84, Bibcode:1998A&A...340...81O.
  2. 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.
  3. 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.
  4. 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.
  5. Lu, Wenxian; et al. (July 2001), "Radial Velocity Studies of Close Binary Stars. IV", The Astronomical Journal, 122 (1): 402–412, arXiv:astro-ph/0104065, Bibcode:2001AJ....122..402L, doi:10.1086/321131.
  6. Kim, Chun-Hwey; et al. (December 2010), "SW Lyncis—Advances and Questions", Journal of Astronomy and Space Sciences, 27 (4): 263–278, Bibcode:2010JASS...27..263K, doi:10.5140/JASS.2010.27.4.263.
  7. "SW Lyn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-07-25.
  8. Kippenhahn, R. (January 1955), "Mitteilungen über 45 verdächtige und veränderliche Sterne", Astronomische Nachrichten (in German), 282 (2): 73–77, Bibcode:1967AJ.....72..493G, doi:10.1002/asna.19552820204.
  9. Vetešnik, M. (1968), "The eclipsing binary system SW Lyncis", Bulletin of the Astronomical Institute of Czechoslovakia, 19: 110, Bibcode:1968BAICz..19..110V.
  10. Gleim, James K. (May 1967), "Photoelectric photometry of SW Lyncis", Astronomical Journal, 72: 493, Bibcode:1967AJ.....72..493G, doi:10.1086/110256.
  11. Vetešnik, M. (1977), "Elements for Spectroscopic and Photometric Close Binary SW Lyn", Bulletin of the Astronomical Institute of Czechoslovakia, 28: 120, Bibcode:1977BAICz..28..120V.
  12. Qingyao, L.; et al. (September 1991), "Photoelectric Photometry Observation and Analysis of the Eclipsing Binary SW Lyn (poster)", International Amateur-Professional Photoelectric Photometry Communication, 45: 37, Bibcode:1991IAPPP..45...37Q.
  13. Kreiner, J. M.; et al. (December 2003), "Physical parameters of components in close binary systems. I", Astronomy and Astrophysics, 412 (2): 465–471, Bibcode:2003A&A...412..465K, doi:10.1051/0004-6361:20031456.
  14. Hinse, T. C.; et al. (September 2014), "An Orbital Stability Study of the Proposed Companions of SW Lyncis", Journal of Astronomy and Space Science, 31 (3): 187–197, arXiv:1409.1368, Bibcode:2014JASS...31..187H, doi:10.5140/JASS.2014.31.3.187, S2CID 54964346.
  15. Avvakumova, E. A.; et al. (October 2013), "Eclipsing variables: Catalogue and classification", Astronomische Nachrichten, 334 (8): 860, Bibcode:2013AN....334..860A, doi:10.1002/asna.201311942, hdl:10995/27061.

Further reading
  • Li, Y.; Qian, S. B. (July 2005), Sterken, C. (ed.), "GMG 2.4-m Telescope and Light-Time Effect Research for W UMa-type Binaries", The Light-Time Effect in Astrophysics, Proceedings of ASP Conference Series, Vol. 335, held in Brussels 19-22 July 2004, San Francisco: Astronomical Society of the Pacific, vol. 335, p. 245, Bibcode:2005ASPC..335..245L.
  • Yoon, Tae Seog; et al. (July 2004), "Observational study of interacting binary stars", New Astronomy Reviews, 48 (9): 759–761, Bibcode:2004NewAR..48..759Y, doi:10.1016/j.newar.2004.03.012.
  • Kim, J. H.; et al. (2002), Ikeuchi, S.; et al. (eds.), "Photometric and Spectroscopic Observations of Three Interacting Binary Systems SW Lyncis, RR Draconis and IQ Persei at the SOAO and the BOAO in South Korea", The Proceedings of the IAU 8th Asian-Pacific Regional Meeting, Volume II, held at National Center of Sciences, Hitotsubashi Memorial Hall, Tokyo, July 2 - 5, 2002, The Astronomical Society of Japan, pp. 437–438, Bibcode:2002aprm.conf..437K.
  • Lu, Wenxian; et al. (July 2001), "Radial Velocity Studies of Close Binary Stars. IV", The Astronomical Journal, 122 (1): 402–412, arXiv:astro-ph/0104065, Bibcode:2001AJ....122..402L, doi:10.1086/321131.
  • Kim, Ho-Il; et al. (December 1999), "Roche Configurations of Two Near-Contact Binaries DO Cas and SW Lyn", Journal of Astronomy and Space Sciences, 16 (2): 209–216, Bibcode:1999JASS...16..209K.
  • Kim, Chun-Hwey (June 1999), "Light-Time Effect and Mass Transfer in the Triple Star SW Lyncis", Journal of Astronomy and Space Sciences, 16 (1): 11–20, Bibcode:1999JASS...16...11K.
  • Kreiner, Jerzy M.; et al. (1997), Leung, Kam-Ching (ed.), "On Period Changes of SW Lyncis", The Third Pacific Rim Conference on Recent Development on Binary Star Research. Proceedings of a conference sponsored by Chiang Mai University, Thai Astronomical Society and the University of Nebraska-Lincoln held in Chiang Mai, Thailand, 26 October -1 November 1995, ASP Conference Series, vol. 130, p. 273, Bibcode:1997ASPC..130..273K.
  • Kim, Ho-Il; Han, Wonyong; Lee, Woo-Baik; Kim, Chun-Hwey (December 1995), "Light Curve Analysis of a Short Period Eclipsing Binary SW Lyncis", Journal of Astronomy and Space Sciences, 12 (2): 196–203, Bibcode:1995JASS...12..196K.
  • Kim, C. H.; Han, W. Y. (January 1993), Leung, Kam-Ching; Nha, Il-Seong (eds.), "A Period Study of SW Lyncis", New frontiers in binary star research : a colloquium sponsored by the U.S. National Science Foundation and the Korean Science and Engineering Foundation, Seoul and Taejon, Korea, November 5-13, 1990, San Francisco, Calif: Astronomical Society of the Pacific, vol. 38, p. 347, Bibcode:1993ASPC...38..347K.
  • Kaluzny, Janusz (1985), "Photometric solutions for seven close binaries of intermediate spectral types: BL And, ST Aqr, DO Cas, TT Her, TZ Lyr, SW Lyn and RU UMi", Acta Astronautica, 35: 327–350, Bibcode:1985AcA....35..327K.
  • Predolin, F.; et al. (June 1980), "Rediscussion of the Photometric Elements of SW Lyn", Information Bulletin on Variable Stars, 1801: 1, Bibcode:1980IBVS.1801....1P.
  • Landolt, Arlo U. (December 1973), "New Minima and Light Elements for the Eclipsing Binary SW Lyncis", Publications of the Astronomical Society of the Pacific, 85 (508): 742, Bibcode:1973PASP...85..742L, doi:10.1086/129539, S2CID 120630787.
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