2016ApJ...826..157C

Silicon monoxide (SiO) masers are rare in star-forming regions, with the exception of five known SiO maser sources. However, we detected two new SiO maser sources from infrared-loud clumps of the high-mass star-forming regions G19.61-0.23 and G75.78+0.34. High angular resolution observations toward G19.61-0.23 suggest that the deeply embedded young stellar object (YSO) of SMA1 is powering the SiO masers. In addition, the SiO v=1, J=1 →0 line shows four spike features, while the v=2 maser shows combined features of one spike and broad wing components, implying energetic activities of the YSO of SMA1 in the G19.61-0.23 hot molecular core. The SiO v=0, J=2 →1 emission shows bipolar outflows in the NE-SW direction with respect to the center of the SiO maser source. A high angular resolution map of the SiO v=1, J=2 →1 maser in G75.78+0.34 shows that the SiO maser is associated with the CORE source at the earliest stage of high-mass star formation. Therefore, the newly detected SiO masers and their associated outflows will provide good probes for investigating this early high-mass star formation.