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Post Info TOPIC: Eclipsing Binary FS Aur-79


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FS Aurigae
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The cataclysmic variable FS Aurigae is in outburst.

Magnitude range: 14.4 - 16.5
Orbital period: 85.7 minutes
Type: SU UMa

Position(2000): RA 05 47 48.36, Dec +28 35 11.1


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Title: FS Aurigae: a Triple Cataclysmic Variable System containing Precessing, Magnetic White Dwarf
Authors: G. Tovmassian, S. Zharikov, C. Chavez, L. Aguilar, J. Tomsick, V. Hambaryan, V. Neustroev

We present here results of numerical calculations demonstrating that the very long periodic variability detected in the Cataclysmic Variable FS Aur can be the result of eccentricity modulation of a close binary (CB) orbit induced by the presence of a third body on a circumbinary orbit. A third component with a substellar mass on a circular, relatively close orbit, modulates the mass transfer rate of the binary on much longer time scales than periods within the triple system. We also report here preliminary results of X-ray observations of FS Aur, providing further evidence that it contains magnetic and freely precessing white dwarf. These two findings allow us to incorporate the new and previously stressed hypothesis on the nature of FS Aur into one consistent model.

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Posts: 131433
Date:
Eclipsing Binary FS Aur-79
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Title: Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79
Authors: S. J. Austin, J. W. Robertson, C. Tycner, T. Campbell, R. K. Honeycutt

The secondary photometric standard star #79 for the FS Aur field (Henden & Honeycutt 1997) designated as [HH97] FS Aur-79 (GSC 1874 399) is a short period (0.2508 days) eclipsing binary whose light curve is a combination of the \beta Lyr and BY Dra type variables. High signal-to-noise multi-colour photometry were obtained using the USNO 1-m telescope. These light curves show asymmetry at quadrature phases (O'Connell effect), which can be modelled with the presence of star spots. A low resolution spectrum obtained with the 3.5-m WIYN telescope at orbital phase 0.76 is consistent with a spectral type of dK7e and dM3e. A radial velocity curve for the primary star was constructed using twenty-four high resolution spectra from the 9.2 m HET. Spectra show H-alpha and H-beta in emission confirming chromospheric activity and possibly the presence of circumstellar material. Binary star models that simultaneously fit the U, B, V, R and RV curves are those with a primary star of mass 0.590.02 Msun, temperature 410025 K, mean radius of 0.67 Rsun, just filling its Roche lobe and a secondary star of mass 0.310.09 Msun, temperature 342525 K, mean radius of 0.48 Rsun, just within its Roche lobe. An inclination angle of 832 degrees with a centre of mass separation of 1.62 Rsun is also derived. Star spots, expected for a rotation period of less than a day, had to be included in the modelling to fit the O'Connell effect.

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