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Session 93 - Binary and Variable Stars.
Oral session, Friday, January 09
Contemporaneous spectroscopic (infrared and optical) and photometric (modified Strömgren) data sets of the short period eclipsing binary V342 Aquilae (period = 3.39 days), providing complete coverage of orbital phase are analyzed in detail. The stellar components are identified as a B7 +/- 2 V primary star and an early G III secondary star with a mass ratio of 0.4 +/- 0.1. The effective temperatures are 10,500 +/- 1,500 (^o)K and 5,000 +/- 1,000 (^o)K. The semi-major amplitude of the primary star radial velocity curve was found to be 90 +/- 5 km/sec from measurements of Si II, H\gamma, He I, Mg II, and H\delta. Ionized ultraviolet emission lines, which cannot be photoionized by the star, dominate the spectra at totality. Strongest are C IV, Mg II, Si IV, and C II, while N V is much weaker. There is a striking similarity to the interacting binary TT Hydrae (B9.5 V+ K0 III).
The stellar parameters and orbital geometry of the system have been determined: masses 3.2 +/- 0.2 and 1.3 +/- 0.5 M_\sun, radii 2.5 and 4.7 R_\sun, Roche lobe radii 7.2 +/- 1.2 R_\sun and 4.7 +/- 0.8 R_\sun, respectively, separation 15.7 R_\sun, and distance to the system 350 +/- 20 pc. Calculations show the mass stream directly hits the gainer and does not form a disk. The ultraviolet spectra outside totality show pronounced Fe II absorption lines arising from ground and metastable levels, indicating an extensive circumstellar gas envelope around the primary. Comparison of synthetic spectra containing the metastable Fe II lines to the observed ultraviolet spectra indicates a temperature of approximately 8,000 (^o)(K), and, assuming solar abundances, a hydrogen column density of 10(^24) cm(^-2). The variation in the absorption spectrum with phase can be explained as entirely due to variation in the velocity field of the gas.
PBE acknowledges support under NSF grant AST-9417035 and RAW acknowledges support under NASA grant NAG 5-1698.
Program listing for Friday