A bright wideband radio burst from the isolated neutron star 2XMM J104608.7$-$594306

Abstract

We present the discovery of a second coherent radio burst from the thermally emitting neutron star 2XMM J104608.7$-$594306 in our follow-up observations with the Murriyang Ultra-Wideband Low receiver. This burst shows complex morphology with multiple components and wideband emission spanning from 704 to 4032MHz. We measured a steep spectral index of $\alpha=-2.18\pm0.16$. Our polarimetric analysis demonstrates that the burst is highly polarised with a linear and circular polarisation fraction of 54% and 22%, respectively. We identified an orthogonal jump in the polarisation position angles of the burst, resembling those seen in radio pulsars. We compared this burst with the first radio burst detected from the source with MeerKAT. These two bursts detected in a total of 40 hours on source with MeerKAT and Murriyang, combined, show that 2XMM J104608.7$-$594306 can emit sporadic radio emission with luminosity jumps comparable to those seen in the bright bursts from SGR 1935+2154. This suggests that previously thought radio-quiet neutron stars such as X-ray dim isolated neutron stars and central compact objects could exhibit rare radio bursting activity.