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A NEW VELOCITY CURVE OF THE RR LYRAE STAR TU URSAE MAJORIS: EVIDENCE FOR DUPLICITY
A. SAHA and R. E. WHITE
Publications of the Astronomical Society of the Pacific
Vol. 102, No. 648 (February 1990), pp. 148-156
Published by: Astronomical Society of the Pacific
Stable URL: http://www.jstor.org/stable/40679476
Page Count: 9
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Spectra taken at the coudé focus of the 5-m Hale telescope were reduced to obtain a velocity curve for the field RR Lyrae star TU UMa. The observations were aimed at detecting differences (if any) in the velocity curves obtained from weak metal lines shortward of the Balmer jump, as opposed to those from similar lines longward of the Balmer jump, so that velocity gradients deep in the atmosphere could be studied. It was not possible to obtain spectra with sufficient S/N and time resolution in the ultraviolet, so only the set of blue spectra could be used. The mean velocity from this velocity curve is different from those measured at earlier epochs. This suggests that TU UMa is a binary system in which the visible component is the RR Lyrae star. The times of maximum light for this star have been known to behave erratically, although the light curve is extremely well behaved and shows no signs of the Blazhko effect. The fluctuations in times of light maxima are interpreted here as time delays due to light travel time as the RR Lyrae component moves in its orbit.
Publications of the Astronomical Society of the Pacific © 1990 The University of Chicago Press