Spatial Structure in the Infrared Spectra of Three Evolved Stars

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Session 46 -- Late Type Stars
Display presentation, Wednesday, 9:20-6:30, Heller Lounge Room

[46.18] Spatial Structure in the Infrared Spectra of Three Evolved Stars

G.C. Sloan, P.C. Tandy (Phillips Lab.), B.E. Pirger (Cornell), T.M. Hodge (Wyoming)

We have spatially resolved three evolved sources using GLADYS, a long-slit 10 $\mu$m spectrometer, at the Wyoming Infrared Observatory. These observations, made in 1993 March, were the first for GLADYS after a complete replacement of the detector drive electronics, ADCs, and hardware co-adder. We studied each source in a north/south and an east/west slit orientation. For each set of observations, we fit a gaussian to the spatial profile at each wavelength to create a spatiogram, or plot of the width of the spectrum as a function of wavelength.

In both slit orientations, the spatiogram of $\alpha$ Orionis is widest at 10 $\mu$m, where the contribution from the silicate dust in the circumstellar shell is strongest. The FWHM at 10 $\mu$m is 2.0 arcsec, while our point-source comparison has a FWHM of 1.6 arcsec. These results are very similar to those presented for a N/S slit by Grasdalen, Sloan, and LeVan (1992, ApJ, 384, L25). IRC+10216 is also resolved in both slit orientations, having a FWHM of 1.9 arcsec at 11 $\mu$m, compared with 1.5 arcsec for a point source. No spectral structure is apparent in the spatiograms, indicating that there is little change in the spectral character of the emission across the source. AFGL 2688 (the Cygnus Egg) is clearly resolved in the N/S slit orientation, where its FWHM at 11 $\mu$m is 2.2 arcsec, but its spatiogram in the E/W slit orientation is barely distinguishable from that of a point source.

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