Previous abstract Next abstract
Session 72 - Late Type Stars and Planetary Nebulae.
Display session, Thursday, June 13
We present preliminary results of our ongoing monitoring campaign of a selected group of more than 30 Long Period Variable (LPV) stars at 10, 11 and 18 \mum. Our stars were chosen from a list by Little-Marenin amp; Little (1990) based upon a classification scheme of silicate features of oxygen rich LPV stars. We are monitoring these LPV's for changes in their silicate features at 10 and 18 \mum with respect to IR continuum and optical phase. We are attempting to ascertain the relationship of dust formation to optical period, and any shell-shock interactions from the acoustic shocks, originating in the photosphere of the stars and later impinging on these dust forming areas. The ultimate goal is to determine what conditions lead to dust formation and destruction in these environments, and whether or not an evolutionary sequence can be inferred for AGB objects based on their spectra and dust formation.
The instrument being used is Denver Univ.'s (DU) TNTCAM (Ten aNd Twenty micron CAMera), a liquid Helium cooled, mid-IR camera using a Rockwell 128x128 Si:As BIB Hybrid Focal Plane Array, sensitive to 26 microns, and housing 7 filters on an externally driven filter wheel (Klebe et al. 1995). A portion of this list of stars was chosen for our initial campaign at Wyoming Infrared Observatory (WIRO) in 1993, including the brightest of our objects with a range of periods and LML types (Creech-Eakman et al. 1996). The rest of our list consists of a sample of LML types with periods of 300-400 days and fluxes of 25 \pm 5 Jy at 8 \mum chosen for one of our ISO proposals. Ancillary mid-IR spectra, exists from LRS on IRAS in '83, our CAESR data from '93, and CGS-3 data from UKIRT service time in '95. We hope to obtain photometric data with TNTCAM and spectral data using ISO's SWS, and TGIRS, DU's new Two Grating mid-IR Spectrometer (Creech-Eakman et al., this meeting). We would like to thank the Univ. of Wyoming for time at WIRO and M. Dahm, T. Eakman, M. Jalakas, D. Klebe amp; B. Lepore for assistance in observing. We also acknowledge the partial support under NASA grant NGT-51290.
Program listing for Thursday