Vaidya metric and Wiki article

[Mentz114]

In the Wiki article http://en.wikipedia.org/wiki/Vaidya_metric it states that

...the Vaidya field is a pure radiation field rather than electromagnetic fields, and the emitted particles have nonzero rest mass.

but it looks to me as if the 'particles' are traveling at the speed of light ( null propagation vector field ) and so must have zero rest mass. Is this a typo or have I misunderstood something ?

 

[Bill_K]

Sure enough, it's a mistake. The matter in the Vaidya metric is what is known as "null dust". Zero mass but incoherent, it can be thought of as the high-frequency limit of electromagnetic radiation.

 

[Mentz114]

Thanks, Bill_K. I've edited the page. Now says 'zero rest mass'.