UV Variability among F+B Interacting Binaries
Session 54 -- Interacting Binaries: Hot Stars
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [54.02] UV Variability among F+B Interacting Binaries

S.B. Parsons (CSC), B.W. Bopp (U. Toledo)

Recent IUE observations at frequent epochs over a 10-week interval are used to explore the time variations in UV spectra and fluxes of 4 binary systems: HD 37453 (F5 II + Be, 66.7d), HD 51956 (F8 Ib + B, 107.4d), HD 59771 (F4 II + B, 89.9d), and PW Pup (F2ep Iab + B, 158d). In addition to having an evolved F primary and a hot secondary, these binaries share the properties of strong H$\alpha$ emission (except 51956), irregular spectral variability, and UV signatures of mass transfer. Results on UV time variations will be shown; the following preliminary conclusions are based on partial completion of the observing program. Relatively small variations of 0.2-0.3 mag are seen for HD 37453 and HD 51956, while HD 59771 shows large changes of 0.5 mag or more. These variations do not appear to correlate with orbital cycle. They may therefore be related to the pulsationally-induced mass dumping phenomenon reported for the prototype for this group of binaries, HD 207739 (Parsons, Dempsey, \& Bopp 1991, IAU Symp. 151, pg. 341). For this system, a saw-toothed UV flux cycle of 50.1d contrasts with the orbital period of 140.8d.

SBP is a staff member of the Space Telescope Science Institute.