AAS 203rd Meeting, January 2004
Session 84 Binary Stars
Poster, Wednesday, January 7, 2004, 9:20am-6:30pm, Grand Hall

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[84.10] Measured Cepheid Masses: U Aql

N. R. Evans (SAO), K. C. Carpenter (NASA's GSFC), R. Robinson (Johns Hopkins Univ.), F. Kienzle (Geneva Obs), M. Albrow (Univ. of Canterbury)

We have obtained an HST STIS ultraviolet high dispersion Echelle mode spectrum of the companion of classical Cepheid U Aql. We have cross-correlated it with a comparable spectrum of a velocity standard (HD 72660) to obtain the velocity difference between the two. We have been able to obtain a velocity signal with the relatively weak S/N, and have had the best results when wavelength regions as large as 40 Åhave been used so that a pattern of features is available in each spectrum. Combining the velocity amplitude of the Cepheid from the ground-based orbit, the orbital velocity of the companion at the phase of HST observation, and the mass of the companion inferred from an IUE low resolution spectrum (1998, ApJ, 484, 768), we have obtained the mass of the Cepheid itself. This work was supported in part by HST grant HST-GO-09146.01-A and by NASA Contract NAS8-39073 to the Chandra X-ray Center.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.