V1191 Cygni

V1191 Cygni is the variable star designation for an overcontact binary star system in the constellation Cygnus.[12] First found to be variable in 1965, it is a W Ursae Majoris variable with a maximum apparent magnitude 10.82. It drops by 0.33 magnitudes during primary eclipses with a period of 0.3134 days, while dropping by 0.29 magnitudes during secondary eclipses.[10] The primary star, which is also the cooler star, appears to have a spectral type of F6V, while the secondary is slightly cooler with a spectral type of G5V.[3] With a mass of 1.29 solar masses and a luminosity of 2.71 solar luminosities, it is slightly more massive and luminous than the sun, while the secondary is only around 1/10 as massive and less than half as luminous. With a separation of 2.20 solar radii, the mass transfer of about 2×10−7 solar masses per year from the secondary to the primary is one of the highest known for a system of its type.[9]

V1191 Cygni
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 20h 16m 50.8045s[1]
Declination +41° 57′ 41.360″[1]
Apparent magnitude (V) 10.99[2]
Characteristics
Spectral type F6V + G5V[3]
Apparent magnitude (B) 11.41[2]
Apparent magnitude (R) 10.55[4]
Apparent magnitude (I) 10.06[5]
Apparent magnitude (J) 9.82[6]
Apparent magnitude (H) 9.56[6]
Apparent magnitude (K) 9.51[6]
B−V color index 0.62[7]
Variable type W UMa[8]
Astrometry
A
Proper motion (μ) RA: 38.4 ± 1.7[2] mas/yr
Dec.: 25.1 ± 1.6[2] mas/yr
Distance278 ± 31[9] pc
Absolute magnitude (MV)3.82[9]
B
Absolute magnitude (MV)5.73[9]
Orbit
Period (P)0.3134 d[10]
Semi-major axis (a)2.182 R☉[11]
Details
A
Mass1.29 ± 0.08[9] M☉
Radius1.31 ± 0.18[9] R☉
Luminosity (bolometric)2.71 ± 0.44[9] L☉
Surface gravity (log g)4.31[9] cgs
Temperature6500[9] K
Age3.85 ± 0.21[11] Gyr
B
Mass0.13 ± 0.01[9] M☉
Radius0.52 ± 0.15[9] R☉
Luminosity (bolometric)0.46 ± 0.08[9] L☉
Surface gravity (log g)4.12[9] cgs
Temperature6610 ± 200[9] K
Age3.85 ± 0.21[11] Gyr
Other designations
GSC 03159-01512, 2MASS J20165081+4157413, SBC9 2996, TYC 3159-1512-1
Database references
SIMBADdata

V1191 Cygni is a W-type W UMa variable,[7] meaning that the primary eclipse occurs when the less-massive component is eclipsed by the larger, more massive component, although the masses are unusually different for such a system.[13] The current period is very short for a system of its spectral type, suggesting that the stars are relatively small for their mass and age,[13] which is likely around 3.85 billion years.[11] The pair's orbital period is increasing at a rate of over 4×10−7 days per year, one of the fastest known rates among contact binary systems,[7] likely due to the high rate of mass transfer. In addition to the period increase, there is cyclic period change of 0.023 days over 26.7 years, caused by either a third body with a mass of 0.77 solar masses or magnetic activity cycles. The mass transfer will likely eventually cause the system to evolve into a single star with a very high rotation rate.[12]

References
  1. Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
  2. Høg, E.; et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  3. Avvakumova, E.A.; Malkov, O.Yu.; Kniazev, A.Yu. (2013). "Eclipsing variables: Catalogue and classification". Astronomische Nachrichten. 334 (8): 860–865. Bibcode:2013AN....334..860A. doi:10.1002/asna.201311942. hdl:10995/27061.
  4. Ivanov, G. A. (2008). "Catalogue of stars with high-proper motions - version 2". Kinematika I Fizika Nebesnykh Tel. 24: 480. Bibcode:2008KFNT...24..480I.
  5. Droege, Thomas F.; Richmond, Michael W.; Sallman, Michael P.; Creager, Robert P. (2006). "TASS Mark IV Photometric Survey of the Northern Sky". Publications of the Astronomical Society of the Pacific. 118 (850): 1666–1678. arXiv:astro-ph/0610529. Bibcode:2006PASP..118.1666D. doi:10.1086/510197. S2CID 11716917.
  6. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: University of Massachusetts and Infrared Processing and Analysis Center. 2246: 0. Bibcode:2003yCat.2246....0C.
  7. Pribulla, T.; Vaňko, M.; Chochol, D. R.; Parimucha, Š.; Baluďanský, D. (2005). "Ccd Photometry of the Neglected Contact Binaries V344 Lac and V1191 Cyg". Astrophysics and Space Science. 296 (1–4): 281–284. Bibcode:2005Ap&SS.296..281P. doi:10.1007/s10509-005-4831-2. S2CID 189843557.
  8. Mayer, P (1965). "Two new variable stars in the Cygnus". Bulletin of the Astronomical Institute of Czechoslovakia. 16: 255–256. Bibcode:1965BAICz..16..255M.
  9. Ulaş, B.; Kalomeni, B.; Keskin, V.; Köse, O.; Yakut, K. (2012). "Marginally low mass ratio close binary system V1191 Cyg". New Astronomy. 17 (1): 46–49. arXiv:1107.0277. Bibcode:2012NewA...17...46U. doi:10.1016/j.newast.2011.06.002. S2CID 119251171.
  10. Malkov, O. Yu.; Oblak, E.; Snegireva, E. A.; Torra, J. (2006). "A catalogue of eclipsing variables". Astronomy and Astrophysics. 446 (2): 785–789. Bibcode:2006A&A...446..785M. doi:10.1051/0004-6361:20053137.
  11. Yildiz, M. (2013). "Origin of W UMa-type contact binaries - age and orbital evolution". Monthly Notices of the Royal Astronomical Society. 437 (1): 185–194. arXiv:1310.5526. Bibcode:2014MNRAS.437..185Y. doi:10.1093/mnras/stt1874. S2CID 119121897.
  12. Zhu, L. Y.; Qian, S. B.; Soonthornthum, B.; He, J. J.; Liu, L. (2011). "Deep, Low Mass Ratio Overcontact Binary Systems. Xi. V1191 Cygni". The Astronomical Journal. 142 (4): 124. Bibcode:2011AJ....142..124Z. doi:10.1088/0004-6256/142/4/124.
  13. Rucinski, S. M.; Pribulla, T.; Mochnacki, S. W.; Liokumovich, E.; Lu, W.; Debond, H.; De Ridder, A.; Karmo, T.; Rock, M.; Thomson, J. R.; Ogłoza, W.; Kaminski, K.; Ligeza, P. (2008). "Radial Velocity Studies of Close Binary Stars. Xiii". The Astronomical Journal. 136 (2): 586–593. arXiv:0805.1695. Bibcode:2008AJ....136..586R. doi:10.1088/0004-6256/136/2/586. S2CID 119225926.
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