R. J. Spivey argues that “Coincident down-chirps in GW150914 betray the absence of event horizons”. The LIGO discovery is said to confirm Einstein’s gravitation theory, yet Einstein (in 1939) gave mathematical grounds for dismissing the notion that black holes exist, points out Spivey. His article uses secondary signals seen in both LIGO detectors (Fig. below)
It’s well appreciated that close binaries of compact stellar objects (neutron stars) are strong sources of gravitational waves – the energy loss in the waves causes the orbits to spiral inwards until the objects are disrupted or merge. The LIGO gravitational wave pulses show the predicted oscillating signal of directional beamed waves, increasing in frequency corresponding to the shrinking orbits.
The LIGO community was so taken with this ‘chirp’ of increasing frequency (curving upwards in the Fig.) and the finding that the mass associated with ‘chirp’ models is much bigger than normal stars (totals ~20 and 65 solar masses Ms in the two LIGO instances) that they failed to look at details in the spectrogram. They largely embraced the claim that the objects must be fashionable ‘black holes’ rather than supermassive neutron stars or other extreme matter. They’ve dismissed these as ‘exotic’ matter, whereas the ‘event horizon’ that delays mass accretion into black-holes for infinite time is the real ‘exotic’ physics.
The last stage of the LIGO signals, as the inspiralling objects touch and merge, would distinguish between models. It’s expected that oscillations depend on a boundary or a ‘horizon’. But this stage is lost in the signal noise, below the detection threshold. Robin Spivey points out an earlier secondary signal – from 160ms, a ‘down-chirp’ of decreasing frequency – provides some evidence. The spectral traces from the two detectors (at Hanford and Livingstone, Fig. above) would match ejection of a fraction of the matter with a launch radial velocity ~ 0.04c. (Other secondary spectral features are ‘noise’, differing in the two detectors.)
Was disruption not expected, associated with the violent inspiralling ? Gigantic amounts of energy are emitted in gravitational waves, equivalent to 3 solar masses (3Msc2 in the larger case). Calculations for a binary of unequal point-masses do find that the smaller mass can be expelled at high (sub-relativistic) speed. Strong perturbations of extended bodies might well expel significant amounts of matter from their fringes. Non-radial instabilities have been indicated in a model ‘gravastar’, implying asymmetric break-up. On the other hand, disruption of a black-hole is inconceivable – is this why the LIGO community have overlooked the ‘down-chirp’ signal ?