THE UNITED KINGDOM INFRARED TELESCOPE
ANNUAL REPORT
1995 AND 1996

2. Scientific Results during 1995 and 1996

2.1. Highlights from Semesters 95A, 95B, 96A, and 96B

2.1.2. Star Formation, the Interstellar Medium, and Stellar Evolution

D. Ward-Thompson obtained shift-and-add JHKL imaging of about 20 young stellar objects in the Ophiucus dark cloud, discovering at least one new binary system and imaging several known (spectroscopic) binaries for the first time at these wavebands. He reported that his results call into question the recent claim that most pre-main sequence stars are binaries.

P.F. Roche and collaborators obtained CGS4 spectra of a sample of UIR band objects in the 5.0-5.5m region to stu dy the occurrence of the 5.25m feature and measure its profile. The characteristic profile of the feature marks it clearly as a member of the UIR family; the width of the feature (in frequency units) is essentially identical to similarly shaped UIR features at other wavelengths and suggests that a simple relationship may exist between the various features.

M.J. Coe and his students obtained spectra of sixty isolated and binary Be stars in the H and K bands. The observations show that significant changes occur in the spectra of differing spectral classes, thus providing a method for determining the spectral type and class of Be stars from IR spectra alone. This is important for the identification of the optical counterparts in binary systems where the traditional blue end of the spectrum is unavailable due to interstellar reddening. More details on this work are given in § 2.2.4.

Spectra of Type Ia supernovae in their nebular phase were obtained by W.P. Meikle and collaborators in order to test if the light curve is due to the decay of Ni produced in the supern ova event. This is the first time that Type Ia infrared spectra have been obtained at this interesting phase when the cobalt lines should be beginning to give way to those of iron. Cobalt and iron were indeed identified in the CGS4 spectra; the masses of these elements inferred from their line strengths tend to support the Ni hypothesis.

W. Schmutz and co-workers obtained K band velocity-resolved spectra of Cygnus X-3 through one complete orbital period. The velocity shifts seen in the lines of the Wolf-Rayet-like secondary imply a mass function for the binary system of 2.3 M. Assumi ng reasonable values for the mass of the WR star and for the inclination of the system, the compact primary must be a black hole.