V1191 Cygni

V1191 Cygni

A visual band light curve for V1191 Cygni, adapted from Ostadnezhad et al. (2014)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	20h 16m 50.8045s[2]
Declination	+41° 57′ 41.360″[2]
Apparent magnitude (V)	10.99[3]
Characteristics
Spectral type	F6V + G5V[4]
Apparent magnitude (B)	11.41[3]
Apparent magnitude (R)	10.55[5]
Apparent magnitude (I)	10.06[6]
Apparent magnitude (J)	9.82[7]
Apparent magnitude (H)	9.56[7]
Apparent magnitude (K)	9.51[7]
B−V color index	0.62[8]
Variable type	W UMa[9]
Distance		278 ± 31[10] pc
Absolute magnitude (MV)	3.82[10]
B
Absolute magnitude (MV)	5.73[10]
Semi-major axis (a)		2.182 R☉[12]
Details
A
Gyr
SBC9 2996, TYC 3159-1512-1
Database references
SIMBAD	data

V1191 Cygni is the

V1191 Cygni is a W-type W UMa variable,[8] 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.^[14] 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,^[14] which is likely around 3.85 billion years.^[12] 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,^[8] 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.^[13]

References