Which sounds like swamp gas in space, but what do I know.
This summary & the abstract undersells it a bit. IIUC, a precursor/causal strong energy source like a gamma ray burst produced stimulated narrowband emission from the H clouds, effectively forming a natural maser pointed at us
Cool. I was thinking of a book with like some industrial waste accident at solar system scale but natural masters ranks up their with natural Uranium chain reaction in the crust.
space farts
There is a book that talks about this, and many other things related to SETI.