10 Micron Spectra of Long Period Variables

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Session 55 -- Pulsating Variables/Stellar Models
Display presentation, Thursday, 2, 1994, 9:20-6:30

[55.01] 10 Micron Spectra of Long Period Variables

M. Creech-Eakman, R. E. Stencel, D. Klebe, J. Williams (University of Denver)

The University of Denver's \underline{C}old \underline{A}tmospheric \underline{E}mission \underline{S}pectral \underline{R}adiometer (CAESR) is a cryogenically cooled low resolution grating spectrometer which scans the 7.4 to 12.8 $\mu$ region. It has been adapted from its balloon flight capabilities for use with a telescope. Over 70 scans of about 30 different variable and calibration stars were obtained from 1993, Aug. 20 - 24 at the Wyoming Infrared Observatory (WIRO). The data is read from binary form to an ASCII record of on and off-source chops and time signatures at a chop frequency of 10 Hz for scans lasting about 7 minutes. The data, which is recorded in dimensionless counts of grating position and flux intensity, is then calibrated in wavelength and flux space with blackbody curves obtained in the lab. Subtraction of the off-source from on-source chop for each star yields the stellar and dust feature signatures. This subtracted form is then noise-filtered with a Fast Fourier Transform technique on a SPARCstation using IDL software. The resulting signature is then divided by a similarily processed calibration star signature to obtain the silicate signature. A comparison of our results with IRAS Low Resolution Spectrometer data will be presented. We are seeking to establish good evidence with these and future observations to support the theory that the silicate signature varies periodically with the variable star's phase. More observations are needed to ascertain the exact nature of the silicate and variable star phase variability. We plan to upgrade to an array spectrometer to continue this investigation. We thank WIRO and Tracy Hodge for use of the telescope and assistance in its operation. We also thank Charles Dirks for the initial software to read the spectral scans and blackbody calibration data. This research was made possible in part by the generous bequest of William Herschel Womble to the University of Denver, and NASA Space Grant NGT 40014.

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