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Post Info TOPIC: 61 Cygni
Blobrana


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RE: 61 Cygni
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61 Cygni, sometimes called Bessel's Star or Piazzi's Flying Star, is a binary star system in the constellation Cygnus. It consists of a pair of orange K-type dwarf stars separated by 28 arcseconds that orbit each other in a period of about 659 years, forming a visual binary.
Although it appears to be a single star to the naked eye, 61 Cygni is in fact a widely separated binary system, composed of two K class (orange) main sequence stars, 61 Cygni A and 61 Cygni B. The brighter star 61 Cygni A is of apparent magnitude 5.2, the fainter 61 Cygni B is 6.1.
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Ed ~ The binary can be split using just 7 x 50 binoculars.

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61cyg
Spectral type:            K5

Position(2000): RA: 21 06 54.6, Dec:     +38 44 45



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Title: The radii of the nearby K5V and K7V stars 61 Cyg A & B - CHARA/FLUOR interferometry and CESAM2k modeling
Authors: Pierre Kervella (LESIA), Antoine Mérand (CHARA), Bernard Pichon (OCA), Frédéric Thévenin (OCA), Ulrike Heiter, Lionel Bigot (OCA), Theo A. Ten Brummelaar (CHARA), Harold A. Mcalister (CHARA), Stephen T. Ridgway (NOAO), Nils Turner (CHARA), Judit Sturmann (CHARA), Laszlo Sturmann (CHARA), P. J. Goldfinger (CHARA), Christopher Farrington (CHARA)

Context: The main sequence binary star 61 Cyg (K5V+K7V) is our nearest stellar neighbour in the northern hemisphere. This proximity makes it a particularly well suited system for very high accuracy interferometric radius measurements. Aims: Our goal is to constrain the poorly known evolutionary status and age of this bright binary star. Methods: We obtained high accuracy interferometric observations in the infrared K' band, using the CHARA/FLUOR instrument. We then computed evolutionary models of 61 Cyg A & B with the CESAM2k code. As model constraints, we used a combination of observational parameters from classical observation methods (photometry, spectroscopy) as well as our new interferometric radii. Results: The measured limb darkened disk angular diameters are theta_LD(A) = 1.775 ±0.013 mas and theta_LD(B) = 1.581 ±0.022 mas, respectively for 61 Cyg A and B. Considering the high accuracy parallaxes available, these values translate into photospheric radii of R(A) = 0.665 ±0.005 Rsun and R(B) = 0.595 ±0.008 Rsun. The new radii constrain efficiently the physical parameters adopted for the modelling of both stars, allowing us to predict asteroseismic frequencies based on our best-fit models. Conclusions: The CESAM2k evolutionary models indicate an age around 6 Gyrs and are compatible with small values of the mixing length parameter. The measurement of asteroseismic oscillation frequencies in 61 Cyg A & B would be of great value to improve the modelling of this important fiducial stellar system, in particular to better constrain the masses.

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