Measurements of the diffuse Galactic synchrotron spectral index and
  curvature from MeerKLASS pilot data
  21cm intensity mapping experiments are bringing an influx of high spectral
resolution observational data in the $\sim100$ MHz $- 1$ GHz regime. We use
pilot $971-1075$ MHz data from MeerKAT in single-dish mode, recently used to
test the calibration and data reduction scheme of the upcoming MeerKLASS
survey, to probe the spectral index of diffuse synchrotron emission below 1 GHz
within $145^{\circ} < \alpha < 180^{\circ}$, $-1^{\circ} < \delta < 8^{\circ}$.
Through comparisons with data from the OVRO Long Wavelength Array and the Maipu
and MU surveys, we find an average spectral index of $-2.75 < \beta < -2.71$
between 45 and 1055 MHz. By fitting for spectral curvature with a spectral
index of the form $\beta + c \, {\rm{ln}}(\nu / 73~{\rm MHz})$, we measure
$\beta = -2.55 \pm 0.13$ and $c = -0.12 \pm 0.05$ within our target field. Our
results are in good agreement (within $1\sigma$) with existing measurements
from experiments such as ARCADE2 and EDGES. These results show the calibration
accuracy of current data and demonstrate that MeerKLASS will also be capable of
achieving a secondary science goal of probing the interstellar medium.
