AAS 201st Meeting, January, 2003
Session 75. Binaries and Friends
Poster, Wednesday, January 8, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[75.04] Finding Triple Stars Among Cool + Hot Binaries

S.B. Parsons (CSC/STScI)

Out of a sample of 134 systems having evolved primaries, upper main sequence secondaries, and good IUE data, about 10% were already known or suspected to be at least triple systems. Another 10% are now being identified as probable systems having at least 3 components within 3 arcsec of each other. By analysis of IUE spectra and optical photometry, and independent of their angular separation, we have derived \DeltaV between each cool primary and hot secondary. We also derived more accurate component temperatures than are generally possible by classification of the composite spectra. The temperatures and \DeltaV are fitted to isochrones, and component masses are thereby estimated. All available data for each system are then examined for mutual consistency. Some ways in which multiplicity is indicated include: (1) SB1 systems where a greater secondary mass than estimated is needed for consistency with the SB1 parameters; (2) a calculated semi-major axis much smaller than observed; (3) a \DeltaV from above analysis much different from that observed; (4) and similarly, Tycho B and V component magnitudes not consistent with the initial UV-optical analysis. In the newly identified probable triple systems, it is generally the hot secondary which must actually be double. One new triple system, HD 149379, has an F giant in the brief first crossing of the Hertzsprung Gap.

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