  The eruptive variable V838 Monocerotis gained notoriety in 2002 when it
brightened nine magnitudes in a series of three outbursts and then rapidly
evolved into an extremely cool supergiant. We present optical, near-IR, and
mid-IR spectroscopic and photometric observations of V838 Monocerotis obtained
between 2008 and 2012 at the Apache Point Observatory 3.5m, NASA IRTF 3m, and
Gemini South 8m telescopes. We contemporaneously analyze the optical & IR
spectroscopic properties of V838 Monocerotis to arrive at a revised spectral
type L3 supergiant and effective temperature Teff~2000--2200 K. Because there
are no existing optical observational data for L supergiants in the optical, we
speculate that V838 Monocerotis may represent the prototype for L supergiants
in this wavelength regime. We find a low level of Halpha emission present in
the system, consistent with interaction between V838 Monocerotis and its B3V
binary; however, we cannot rule out a stellar collision as the genesis event,
which could result in the observed Halpha activity. Based upon a two-component
blackbody fit to all wavelengths of our data, we conclude that, as of 2009, a
shell of ejecta surrounded V838 Monocerotis at a radius of R=263+/-10 AU with a
temperature of T=285+/-2 K. This result is consistent with IR interferometric
observations from the same era and predictions from the Lynch et al. model of
the expanding system, which provides a simple framework for understanding this
complicated system.
