Massive young stellar objects are known to undergo an evolutionary phase in which high mass accretion rates drive strong outflows .
A class of objects believed to trace this phase accurately is the GLIMPSE Extended Green Object ( EGO ) sample , so named for the presence of extended 4.5 \mu m emission on sizescales of \sim 0.1 pc in Spitzer images .
We have been conducting a multi-wavelength examination of a sample of 12 EGOs with distances of 1 to 5 kpc .
In this paper , we present mid-infrared images and photometry of these EGOs obtained with the SOFIA telescope , and subsequently construct SEDs for these sources from the near-IR to sub-millimeter regimes using additional archival data .
We compare the results from greybody models and several publicly-available software packages which produce model SEDs in the context of a single massive protostar .
The models yield typical R _ { \star } \sim 10 R _ { \odot } , T _ { \star } \sim 10 ^ { 3 } to 10 ^ { 4 } K , and L _ { \star } \sim 1 - 40 \times 10 ^ { 3 } L _ { \odot } ; the median L / M for our sample is 24.7 L _ { \odot } / M _ { \odot } .
Model results rarely converge for R _ { \star } and T _ { \star } , but do for L _ { \star } , which we take to be an indication of the multiplicity and inherently clustered nature of these sources even though , typically , only a single source dominates in the mid-infrared .
The median L / M value for the sample suggests that these objects may be in a transitional stage between the commonly described ‘ ‘ IR-quiet ’ ’ and ‘ ‘ IR-bright ’ ’ stages of MYSO evolution .
The median T _ { dust } for the sample is less conclusive , but suggests that these objects are either in this transitional stage or occupy the cooler ( and presumably younger ) part of the IR-bright stage .