If the Black Holes are colliding at a speed much higher than 0.1%c, that means atoms of the two black holes are colliding at that speed. If atoms are colliding at that speed, we can also say that protons of the two black holes are colliding at that speed. So, it is turning out to be similar to proton-proton collision and some mass would be lost to Light energy or Electro-Magnetic radiation. Incidentally, NASA also detected some Electro-Magnetic radiation from the same source of GW which LIGO detected. But this mass loss to EM radiation is not accounted in the LIGO analysis.
Firstly, and I'm sure you have been told before, any BH is really just critically curved spacetime, with a Singularity in the middle where the mass resides in some unknown state: The EH's are actually colliding [just spacetime] and after they form into one larger BH, the singularities merge into one. No atoms are colliding unless accretion disks are accompanying the BH's concerned.
With the bit on the EM detected by the FERMI, we are not sure, and that depends on trajectory and other factors......
I published the paper concerning that early in the other gravitational wave confirmation thread...here it is again.......
http://arxiv.org/pdf/1602.04735v2.pdf
ELECTROMAGNETIC COUNTERPARTS TO BLACK HOLE MERGERS DETECTED BY LIGO
Abraham Loeb1 Draft version
February 24, 2016
ABSTRACT
Mergers of stellar-mass black holes (BHs), such as GW150914 observed by LIGO, are not expected to have electromagnetic counterparts. However, the Fermi GBM detector identified a γ-ray transient 0.4 s after the gravitational wave (GW) signal GW150914 with consistent sky localization. I show that the two signals might be related if the BH binary detected by LIGO originated from two clumps in a dumbbell configuration that formed when the core of a rapidly rotating massive star collapsed. In that case, the BH binary merger was followed by a γ-ray burst (GRB) from a jet that originated in the accretion flow around the remnant BH. A future detection of a GRB afterglow could be used to determine the redshift and precise localization of the source. A population of standard GW sirens with GRB redshifts would provide a new approach for precise measurements of cosmological distances as a function of redshift.
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Plus this from the SWIFT.......
http://cds.cern.ch/record/612834/files/0304228.pdf
Swift Pointing and the Association Between Gamma-Ray Bursts and Gravitational-Wave Bursts
ABSTRACT
The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested, the black hole progenitor (e.g., coalescing binary or collapsing stellar core) identified, and the origin of the gamma rays (within the expanding relativistic fireball or at the point of impact on the interstellar medium) located. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. To do any of these requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma ray burst observations depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based “figure of merit” that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts.