The following Physical Review D article gives reasonable bounds for gravitational wave detection for Supernova core collapse. These bounds cannot be overwhelmingly different from the bounds on GW detection from compact binary star ("black hole") collapse. However, to meet the LIGO claim of 1.3 billion ly to source, the bounds on detecting a "black hole" merger would have to be ONE or TWO ORDERS OF MAGNITUDE different from those of supernova core collapse. This seems unlikely.
The original article is at Phys. Rev. D 93 042002. If you do not have APS privileges, the article can be read in rough format (please excuse) at: https://integrativemind.wordpress.com/2016/02/24/observing-gravitational-waves-from-core-collapse-supernovae-in-the-advanced-detector-era/ (This is not the most related article, simply one I ran across today.)
Six other reasons I doubt the LIGO results:
1) Against all precedent, the American Physical Society announced the finding with absolute certainty. Major discoveries are always announced tentatively pending input from independent researchers. The Higgs boson discovery, for example, generated dozens of papers in Physical Review D questioning the results. This suggests APS and the LIGO group are exaggerating the claim.
2) The detection occurred right after a system upgrade. Lawrence Krauss at Arizona State University has said that the signal could have been a standard test pattern, accidentally or deliberately injected into the data stream. (https://www.newscientist.com/article/dn28754-new-rumours-that-gravitational-waves-have-finally-been-detected/) Had a test signal caused the detection, no one would admit it, even if they knew. Angry support personnel are not uncommon in astronomical research environments.
3) The signal looks too much like a textbook pattern. Usually an initial discovery has elements of surprise. For example, the predicted CMB temperature was an order of magnitude off from the observed 2.7K.
4) That the "source" was 1.3 billion ly distant is improbable for a first detection, given the weakness of gravitational signals. One would expect the first detection to be nearer the local cluster, out to perhaps 100 million light years (see above PRD article).
5) Physicists (such as James Hartle in personal conversation) admit black holes can never form by gravitational collapse, due to infinite time dilation at the event horizon. Two black holes merging might also be impossible. At best, the LIGO GW might come from a merger of compact binary stars. That they announced it was black holes suggests exaggeration.
6) Astronomical projects need money, and astronomers are known to distort results to insure future funding. Formerly employed at Kitt Peak, I have seen this first hand.