J/A+A/467/1215 Bet Aur light curves (Southworth+, 2007)
Eclipsing binaries observed with the WIRE satellite.
II. beta Aurigae and non-linear limb darkening in light curves.
Southworth J., Bruntt H., Buzasi D.L.
<Astron. Astrophys. 467, 1215 (2007)>
=2007A&A...467.1215S 2007A&A...467.1215S
ADC_Keywords: Binaries, eclipsing ; Photometry
Keywords: stars: fundamental parameters - stars: binaries: eclipsing -
stars: binaries: spectroscopic - stars: distances - stars: evolution -
stars: individual: beta Aurigae
Abstract:
We present the most precise light curve ever obtained of a detached
eclipsing binary star and use it investigate the inclusion of
non-linear limb darkening laws in light curve models of eclipsing
binaries. This light curve, of the bright eclipsing system beta
Aurigae, was obtained using the star tracker aboard the WIRE satellite
and contains 30000 datapoints with a point-to-point scatter of
0.3mmag. We analyse the WIRE light curve using a version of the EBOP
code modified to include non-linear limb darkening laws and to
directly incorporate observed times of minimum light and spectroscopic
light ratios into the photometric solution as individual observations.
We also analyse the dataset with the Wilson-Devinney code to ensure
that the two models give consistent results. EBOP is able to provide
an excellent fit to the high-precision WIRE data. Whilst the
fractional radii of the stars are only defined to a precision of 5% by
this light curve, including an accurate published spectroscopic light
ratio improves this dramatically to 0.5%. Using non-linear limb
darkening improves the quality of the fit significantly compared to
the linear law and causes the measured radii to increase by 0.4%. It
is possible to derive all of the limb darkening coefficients from the
light curve, although they are strongly correlated with each other.
The fitted coefficients agree with theoretical predictions to within
their fairly large error estimates. We were able to obtain a
reasonably good fit to the data using the Wilson- Devinney code, but
only using the highest available integration accuracy and by iterating
for a long time. Bolometric albedos of 0.6 were found, which are
appropriate to convective rather than radiative envelopes. The radii
and masses of the components of beta Aurigae are
RA=2.762±0.017R☉, RB=2.568±0.017R☉,
MA=2.376±0.027M☉ and MB=2.291±0.027M☉, where A and
B denote the primary and secondary star, respectively. Theoretical
stellar evolutionary models can match these parameters for a solar
metal abundance and an age of 450 to 500Myr. The Hipparcos
trigonometric parallax and an interferometrically-derived orbital
parallax give distances to beta Aurigae which are in excellent
agreement with each other and with distances derived using surface
brightness relations and several sets of empirical and theoretical
bolometric corrections.
Description:
The WIRE satellite light curve for beta Aurigae, containing 30015
observations with a point-to-point scatter of 0.3mmag, is given.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
---------------------------------------------
05 59 31.7 +44 56 51 bet Aur = HD 40183
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 26 30015 WIRE satellite light curve of beta Aurigae
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See also:
J/A+A/456/651 : psi Cen light curves (Bruntt+, 2006)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 F15.7 d HJD Heliocentric Julian Date of the observation
17- 26 F10.7 mag dmag Differential magnitude of beta Aurigae
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Acknowledgements:
John Southworth, jkt(at)astro.keele.ac.uk
References:
Bruntt et al., Paper I 2006A&A...456..651B 2006A&A...456..651B, Cat. J/A+A/456/651
(End) John Southworth [Warwick Uni., UK], Patricia Vannier [CDS] 19-Mar-2007