Other
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........22f&link_type=abstract
Thesis (PH.D.)--STATE UNIVERSITY OF NEW YORK AT STONY BROOK, 1994.Source: Dissertation Abstracts International, Volume: 56-03,
Other
Scientific paper
We present infrared spectrophotometry and intermediate resolution (lambda/Deltalambda ~50)^ectroscopy of beta Pictoris and other early-type main sequence stars with infrared excesses. Spectrophotometric observations were conducted in the narrowband (Delta lambda~1mu m) "silicate" filters with the MSFC bolometer array camera and the IRTF 2-30 μm Facility bolometer system. Spectroscopic observations were conducted with the 3-14 mu m Aerospace Corp. Infrared Spectrograph. These observations were motivated by the previously reported detection of silicate emission in beta Pic. We detected 10 μm silicate emission from the B9.5 Ve star 51 Oph. We show that the silicate features of beta Pic and 51 Oph are broader and exhibit more structure than the features from amorphous and/or hydrated silicates, such as found in the interstellar medium or in most circumstellar shells of M stars. The 10 μm silicate feature of beta Pic and 51 Oph is similar to that in several Solar System comets. The presence of high temperature phases of silicates such as olivines and pyroxenes is evident in the beta Pic and 51 Oph spectra, as in the case of comets and interplanetary dust particles. In a subsequent photometric survey of ten beta Pic analogs, we obtained the most precise determinations of their mid-infrared excesses. None of these ten sources showed the prominent silicate feature of beta Pic and 51 Oph. The 10 μm excess fluxes of zeta Lep and beta UMa suggest the presence of weak silicate emission. Intermediate-resolution spectra of these two sources are similar to the weak and broad emission features seen in dust-poor comets. We searched for gaseous spectral features around 2.3 μm from CO overtone transitions (nu = 0-2) in beta Pic and analogous systems. We utilized the high -resolution near-infrared Echelle spectrograph (CSHELL) at the IRTF. Our inferred upper limits to circumstellar CO column density in beta Pic possibly indicate an enhancement of CO abundance such as observed in cometary environments.
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