What happens when two D-branes annihilate? Do we get a radiation of strings?
My answer to your question is in the context of brane inflation. The mechanism is as follows: A pair of D3 and Anti D3 separated by a warped dimension (Bulk), move closer until the separation of the branes is about the string length scale, then a stretched tachyon forms creating an instability that destroys both branes, releasing all the energy to closed string states. Since radiation is included in the spectrum of closed strings, both particles and radiation are produced.