V1191 Cygni

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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
Distance 278 ± 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
Mass 1.29 ± 0.08[9] M☉
Radius 1.31 ± 0.18[9] R☉
Luminosity (bolometric) 2.71 ± 0.44[9] L☉
Surface gravity (log g) 4.31[9] cgs
Temperature 6500[9] K
Age 3.85 ± 0.21[11] Gyr
B
Mass 0.13 ± 0.01[9] M☉
Radius 0.52 ± 0.15[9] R☉
Luminosity (bolometric) 0.46 ± 0.08[9] L☉
Surface gravity (log g) 4.12[9] cgs
Temperature 6610 ± 200[9] K
Age 3.85 ± 0.21[11] Gyr
Other designations
GSC 03159-01512, 2MASS J20165081+4157413, SBC9 2996, TYC 3159-1512-1
Database references
SIMBAD data

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 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

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  1. ↑ 1.0 1.1 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 6.2 Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7.0 7.1 7.2 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 9.13 Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ 11.0 11.1 11.2 11.3 Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ 12.0 12.1 Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ 13.0 13.1 Lua error in package.lua at line 80: module 'strict' not found.
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