When I saw the report of a gamma ray burst associated with the LIGO GW event, my immediate thought was that the obvious explanation is that the compact massive objects were not in fact black holes, and the gamma ray burst was from the energy of the final collision and merger. This would obviously mean that Einstein's Field Equations would have to be inaccurate at this extreme limit of very strong fields, but as far as I know they have not been experimentally confirmed in this regime anyway, so I would expect this to be worth investigating, especially when balanced against theories such as Loeb's idea about the merger occurring inside a star. (The alternative option that Einstein's Field Equations are correct even in that case but the object somehow manages to resist gravitational collapse is not mathematically viable for masses as large as those involved in the GW event). There are of course various clues which suggest that there is a threshold mass which distinguishes between neutron stars and something else, which for example doesn't show thermonuclear flashes from a surface or pulsar emissions, and which is assumed to be a stellar-mass black hole. However, there are few cases where all of the parameters can be pinned down, and there are some definite anomalies, such as ULX source M82X-2 which was thought to be well into the black hole range from its luminosity, but was then found to be a pulsar, and is still essentially unexplained by any standard theory as far as I know. Is there any other direct evidence (apart from the intrinsic neatness of GR theory) for the existence of stellar-mass black holes as opposed to some sort of extremely dense but non-collapsed object? Has anyone spotted any serious scientific discussions of whether the gamma-ray burst might suggest that black holes do not occur (at least at this mass range)?