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Session 45 - Eclipsing Binaries.
Display session, Thursday, January 08
Exhibit Hall,

[45.12] A Differential Analysis for the Determination of Atmospheric Parameters, Flux Measurement Errors, and Abundances in V356 Sgr

S. W. Roby, D. A. Armstrong, J. M. Hassett, K. E. Mauser, J. D. Wanek (SUNY Oswego), R. S. Polidan (NASA/GSFC)

The eclipsing, interacting binary system, V356 Sgr, is composed of an A2II star which has previously undergone mass transfer to its B3V companion. Our team of undergraduate researchers are examining a large number of IUE low and high dispersion archival spectra to examine many aspects of this complex system.

Ultraviolet spectra of the individual stars have been obtained by appropriate manipulation of the merged IUE NEWSIPS SWP and LWP low dispersion spectra taken during eclipse and combined light phases and by modeling of the scattered light. To determine the effective temperatures and gravities of the A and B stellar components, we have compared the resulting spectra to a grid of Kurucz solar metallicity models. To calibrate our technique and minimize any systematic errors, we have also fitted Kurucz models to a few well-studied stars of similar spectral types. UV light curves were generated from flux averages for selected 20 A bands in the IUE SWP spectra. Determination of the internal and external sources of error in our flux measurements are evaluated using standard IUE data analysis procedures and from analyzing identical measurements of a "spectral twin" to the B star component in V356 Sgr. This reference star, HD 60753, is of similar magnitude to V356 Sgr and has been observed with IUE over a similar time frame using similar exposure times. The characteristics of the light curve and initial modeling results will be presented.

Preliminary differential abundance analyses are presented for Fe, C and N using the standard stars Gamma Peg and Gamma Gem as comparison stars for the B and A stars of V356 Sgr, respectively. These results are discussed with respect to the presence of CNO processed material in the surface layers of the A star and the B star, along with implications for mass accretion onto the B star.

This work was supported in part by a NASA/University Joint Venture (JOVE) grant to SUNY Oswego.

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