Radio Observations of Supernova Remnant G1.9+0.3
  We present 1 to 10GHz radio continuum flux density, spectral index,
polarisation and Rotation Measure (RM) images of the youngest known Galactic
Supernova Remnant (SNR) G1.9+0.3, using observations from the Australia
Telescope Compact Array (ATCA). We have conducted an expansion study spanning 8
epochs between 1984 and 2017, yielding results consistent with previous
expansion studies of G1.9+0.3. We find a mean radio continuum expansion rate of
($0.78 \pm 0.09$) per cent year$^{-1}$ (or $\sim8900$ km s$^{-1}$ at an assumed
distance of 8.5 kpc), although the expansion rate varies across the SNR
perimeter. In the case of the most recent epoch between 2016 and 2017, we
observe faster-than-expected expansion of the northern region. We find a global
spectral index for G1.9+0.3 of $-0.81\pm0.02$ (76 MHz$-$10 GHz). Towards the
northern region, however, the radio spectrum is observed to steepen
significantly ($\sim -$1). Towards the two so called (east & west) "ears" of
G1.9+0.3, we find very different RM values of 400-600 rad m$^{2}$ and 100-200
rad m$^{2}$ respectively. The fractional polarisation of the radio continuum
emission reaches (19 $\pm$ 2)~per~cent, consistent with other, slightly older,
SNRs such as Cas~A.
