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BV photometry of quadrupole system ET Bootis
In this study, we present the first Johnson BV photometry of theeclipsing binary star ET Bootis, which is member of a physicallyconnected visual pair. Analysis of times of light minima enables us tocalculate accurate ephemeris of the system via O-C analysis andobserved an increase in period which we believe is a result of thelight-time effect in the outer visual orbit. Secondly, we determined thetotal brightness and color of the system in light maxima and minima.Photometric solution of the system indicates that the contribution ofthe visual pair to the total light is about 40% in Johnson V band.Furthermore, photometric analysis shows that the primary star in theeclipsing binary has F8 spectral type while it confirms the G5 spectraltype for the visual pair. Masses of the components in eclipsing binaryare M1 = 1.109 ± 0.014 M&sun; andM2 = 1.153 ± 0.011 M&sun;. Absolute radiiof the components are R1 = 1.444 ± 0.007R&sun; and R2 = 1.153 ± 0.007R&sun;. Physical properties of the components leads 176± 7 pc distance for the system and suggests an age of 6.5 billionyears.
| Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| CCD Times of Minima of Some Eclipsing Binaries in 2002
We present CCD observations of minima of 11 eclipsing binaries.
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