First high-resolution radio study of the Supernova Remnant G338.3-0.0
  associated with the gamma-ray source HESS J1640-465
  We report on a multifrequency radio study of the supernova remnant (SNR)
G338.3-0.0, in positional coincidence with the TeV source HESS J1640-465. To
carry out this research we observed the SNR G338.3-0.0 using the Giant
Metrewave Radio Telescope (GMRT) at 235, 610, and 1280 MHz. We also reprocessed
archival data from the Australia Telescope Compact Array (ATCA) at 1290 and
2300 MHz. Also we conducted a search for radio pulsations towards a central
point-like source, using the GMRT antennas at 610 and 1280 MHz. The molecular
material in the region of the SNR was investigated based on observations made
with the NANTEN telescope in the 12^CO (J=1-0) emission line. The new radio
observations revealed a remnant with a bilateral morphology, which at 235 MHz
has the western wing completely attenuated because of absorption due to
foreground ionized gas. The quality of the new images allows us to provide
accurate estimates for the total radio flux density of the whole SNR at
different radio frequencies. From the new and existing flux density estimates
between 235 and 5000 MHz we derived for the whole remnant a spectral index
alpha=-0.51 +/-0.06 with a local free-free continuum optical depth at 235 MHz
tau_{235}=0.9+/-0.3. No radio pulsations were detected towards the only radio
point-like source within the HESS error circle. We derived upper limits of 2.0
and 1.0 mJy at 610 and 1280 MHz, respectively, for the pulsed flux towards this
source. No radio counterpart was found for the pulsar wind nebula discovered in
X-rays. The inspection of the interstellar molecular gas towards G338.3-0.0 and
surroundings revealed that there is not any associated dense cloud that might
explain a hadronic origin for the TeV detection.
