On the properties of dust and gas in the environs of V838 Monocerotis
  Herschel FIR imaging and spectroscopy were taken at several epochs to probe
the central point source and the extended environment of V838 Mon. PACS and
SPIRE maps were used to obtain photometry of the near and far dust around V838
Mon. Fitting reveals 0.5-0.6 solar masses of ~19K dust in the environs (~2.7pc)
surrounding the star. The surface-integrated infrared flux (signifying the
thermal light echo) and derived dust properties do not vary significantly
between the epochs. We also fit the SED of the point source. As the peak of the
SED lies outside the Herschel spectral range, it is only by incorporating data
from other observatories and epochs that we can perform useful fitting; with
this we explicitly assume no evolution of the point source between the epochs.
We find warm dust with a temperature of ~300K distributed over a radius of
150-200AU. PACS and SPIRE spectra were also used to detect emission lines from
the extended environment around the star. We fit the far-infrared lines of CO
arising from the point source, from an extended environment around V838 Mon.
Assuming a model of a spherical shell for this gas, we find that the CO appears
to arise from two temperature zones: a cold zone (Tkin ~18K) that could be
associated with the ISM or possibly with a cold layer in the outermost part of
the shell, and a warm (Tkin ~400K) zone that is associated with the extended
environment of V838 Mon within a region of radius of ~210AU. The SiO lines
arise from a warm/hot zone. We did not fit the lines of H2O as they are far
more dependent on the model assumed.
