The Peculiar Radio Source M17 JVLA 35
  M17 JVLA 35 is a radio source detected in projection against the M17 HII
region. In recent observations, its spectrum between 4.96 and 8.46 GHz was
found to be positive and very steep, with $\alpha \geq 2.9 \pm 0.6$ ($S_\nu
\propto \nu^\alpha$). Here we present Very Large Array observations made in the
18.5 to 36.5 GHz region that indicate a spectral turnover at $\sim$13 GHz and a
negative spectral index ($\alpha \simeq -2.0$) at higher frequencies. The
spectrum is consistent with that of an extragalactic High Frequency Peaker
(HFP). However, M17 JVLA 35 has an angular size of $\sim0\rlap.{''}5$ at 8.46
GHz, while HFPs have extremely compact, milliarcsecond dimensions. We discuss
other possible models for the spectrum of the source and do not find them
feasible. Finally, we propose that M17 JVLA35 is indeed an HFP but that its
angular size becomes broadened by plasma scattering as its radiation travels
across M17. If our interpretation is correct, accurate measurements of the
angular size of M17 JVLA35 across the centimeter range should reveal the
expected $\nu^{-2}$ dependence.
