  Archival optical spectra from the Sloan Digital Sky Survey of two optically
faint flat spectrum protostars, IRAS 04369+2539 and IRAS 05451+0037, show
strong emission-line features including -- notably -- clear and broad emission
across several molecular bands of TiO and VO. The molecular emission is
indicative of dense, warm circumstellar gas and has been seen previously in
only one object: the flat spectrum protostar IRAS 20496+4354 during a strong
optical outburst (PTF 10nvg; Covey et al. 2011). The presence of broad
molecular emission features in two additional objects having similar
mid-infrared properties (but not known to be undergoing outbursts) could
provide new insight into phases of rapid accretion / outflow at early stages of
the protoplanetary disk. At present, the relevant geometry and the formation or
heating mechanisms responsible for the observed TiO / VO cooling emission
remain unexplained.
