Mid-Infrared Photometry and Spectra of Three High-Mass Protostellar Candidates at IRAS 18151-1208 and IRAS 20343+4129

We present arcsecond-scale mid-IR photometry (in the 10.5 μm N band and at 24.8 μm), and low-resolution spectra in the N band (R simeq 100) of a candidate high-mass protostellar object (HMPO) in IRAS 18151-1208 and of two HMPO candidates in IRAS 20343+4129, IRS 1 and IRS 3. In addition, we present high-resolution mid-IR spectra (R simeq 80,000) of the two HMPO candidates in IRAS 20343+4129. These data are fitted with simple models to estimate the masses of gas and dust associated with the mid-IR-emitting clumps, the column densities of overlying absorbing dust and gas, the luminosities of the HMPO candidates, and the likely spectral type of the HMPO candidate for which [Ne II] 12.8 μm emission was detected (IRAS 20343+4129 IRS 3). We suggest that IRAS 18151-1208 is a pre-ultracompact H II region HMPO, IRAS 20343+4129 IRS 1 is an embedded young stellar object with the luminosity of a B3 star, and IRAS 20343+4129 IRS 3 is a B2 ZAMS star that has formed an ultracompact H II region and disrupted its natal envelope.