G34.24+0.13MM: A Deeply Embedded Proto–B Star

Abstract

By means of millimeter and submillimeter imaging, we have identified a massive protostellar object that coincides with a methanol maser and is not detectable in the continuum at centimeter wavelengths. Located 84" (1.5 pc) southeast of the ultracompact H II (UCHII) region G34.26+0.15, the new object G34.24+0.13MM was discovered in a wide-field 350 μm continuum image obtained with the Submillimeter High Angular Resolution Camera (SHARC) at the Caltech Submillimeter Observatory (CSO). Interferometric imaging at 225.7 and 110.7 GHz continuum has determined more precisely the position and angular diameter (2".0, or 7600 AU) of the object. No source was detected at that position in 1.2-3.7 μm imaging or 10 and 20 μm photometry. Our observations are consistent with a cool dust core with temperature ~50 K, total gas mass 100 M_☉, and total luminosity in the range of 1600-6300 L_☉. Considering the high luminosity and lack of compact radio continuum emission, we conclude that this core probably contains a deeply embedded proto-B star.

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