The interior of the SNR RX J0852.0-4622 (Vela Jr) at radio wavelengths

Aims. We observed the center of the supernova remnant Vela Jr in radio continuum in order to search for a counterpart to the compact central X-ray source CXOU J085201.4- 461753, possibly a neutron star candidate which could be the remnant of the supernova explosion. Methods. Observations were made with the Australia Telescope Compact Array at 13 and 20 cm. Spectral indices were obtained using flux density correlations of the data which were spatially filtered to have the same u - v coverage. A multiwavelength search for counterparts to the compact central X-ray source was made. Results. We compiled a new catalogue of 31 small diameter radio sources, including the previously known source PMN J0853- 4620, listing the integrated flux densities at 20 cm and, for half of the sources, the flux densities at 13 cm with the corresponding spectral indices. All sources are unresolved at the present angular resolution except for Source 18, which is clearly elongated and lies strikingly close to CXOU J085201.4- 461753. Our observations show no evidence for the existence of a pulsar wind driven nebula associated with the point X-ray source. Furthermore, Source 18 has a thermal spectrum with index alpha = + 0.8 +/- 0.4 (S proportional to nu(alpha)), and appears to be the counterpart of the optical source Wray 16-30. In spite of the absence of [O III] emission lines as reported in the literature, we find that this object could be explained as a low emission planetary nebula belonging to the "butterfly" morphological class. Conclusions. We conclude that if the radio source 18 is actually a planetary nebula, then CXOU J085201.4- 461753 is more likely to be related to it rather than to Vela Jr.