LIGO August 2017 Assessment

We have been asked about the veracity of the Report that LIGO has discovered gravitational waves from the merger of two neutron stars, and that the FERMI satellite and ground observations were involved. This was widely reported in the Press such as the New York Times and the BBC here:

LIGO Detects Fierce Collision of Neutron Stars for the First Time

Einstein's waves detected in star smash

According to the SED model, gravitational waves do occur, but in a different way to that proposed by Einstein. Some details are on page 289 of the Monograph. The question actually becomes whether or not the LIGO instrument has picked up these waves or some other artefact.  The following comment from a discussion on the net is interesting:

"This is nothing more than LIGO trying to ride the coattails of Fermi's GRB observation and shoehorn in their supposed gravitational wave detection. This supposed loudest of all GW detections started out as a low-latency signal from only one of the LIGO detectors, so low it was ignored! The LIGO team went back and massaged the data to get it to better fit the Fermi gamma-ray observation, INTEGRAL timings, and then the subsequent observations of what is obviously a supernova."

To this end, I first checked on the sequence of events. A report by NASA confirms that the Fermi Gamma Ray Space Telescope was the first one to pick up the signals. The NASA report begins as follows:

“Shortly after 8:41 a.m. EDT on Aug. 17, NASA's Fermi Gamma-ray Space Telescope picked up a pulse of high-energy light from a powerful explosion, which was immediately reported to astronomers around the globe as a short gamma-ray burst. The scientists at the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves dubbed GW170817 from a pair of smashing stars tied to the gamma-ray burst, encouraging astronomers to look for the aftermath of the explosion. Shortly thereafter, the burst was detected as part of a follow-up analysis by ESA’s (European Space Agency’s) INTEGRAL satellite.”

Thus Fermi did indeed pick up the first signals. The LIGO collaboration then became involved but soon thereafter the INTEGRAL satellite picked up the signal of the burst.  It continued:

“Within hours of the initial Fermi detection, LIGO and the Virgo detector at the European Gravitational Observatory near Pisa, Italy, greatly refined the event's position in the sky with additional analysis of gravitational wave data. Ground-based observatories then quickly located a new optical and infrared source -- the kilonova -- in NGC 4993.” [emphasis added]

So it took a number of hours for the LIGO group to “refine” their data and to “analyze” it to confirm the event and to obtain, with the help of the European Virgo detector a likely position for the event. The full report is NASA Missions Catch First Light from a Gravitational-Wave Event

The account from the INTEGRAL group states in part

“We report the INTernational Gamma-ray Astrophysics Laboratory (INTEGRAL) detection of the short gamma-ray burst GRB 170817A (discovered by Fermi-GBM) with a signal-to-noise ratio of 4.6, and, for the first time, its association with the gravitational waves (GWs) from binary neutron star (BNS) merging event GW170817 detected by the LIGO and Virgo observatories.” [emphasis added]

The article goes on:

“2017 August 17 at 12:41:04.47 UTC, a signal consistent with the merger of a BNS was detected by the LIGO-Hanford detector (LIGO Scientific Collaboration et al. 2015) as a single-detector trigger. The subsequent alert was issued in response to a public real-time Fermi Gamma-ray Burst Monitor (GBM) trigger on an sGRB at 12:41:06.48 UTC.” [emphasis added]

Note the alert was given because of the Fermi monitor data. Only one of the two LIGO detectors had picked up any signal and so automatically did not trigger any alert; both detectors (Hanford as well as Livingston) need to pick up an event to activate a trigger.
The Integral Report goes on:

“Analysis of the LIGO–Livingston data (LIGO Scientific Collaboration & Virgo Collaboration 2017e) revealed that a trigger was not automatically issued due to the proximity of an overflow instrumental transient, which could be safely removed offline. The addition of Virgo (Acernese et al. 2015) to the detector network allowed a precise localization at 90% confidence level in an area of about 31 square degrees.” [emphasis added]

That is jargon for saying that the data in LIGO had to be treated mathematically to remove the suspected transient and produce a result. And then the Virgo collaborators had to be brought in to boost the confidence level. All this can be found in the Report.

Details of the mathematical treatment of the LIGO data were given in an article by the LIGO collaboration. In the caption under Figure 2 and the bottom panel, we find the following comment:

Bottom panel: The raw LIGO-Livingston strain data (orange curve) showing the glitch in the time domain. To mitigate the glitch in the rapid reanalysis that produced the sky map shown in Fig. 3 [77], the raw detector data were multiplied by an inverse Tukey window (gray curve, right axis) that zeroed out the data around the glitch [73]. To mitigate the glitch in the measurement of the source’s properties, a model of the glitch based on a wavelet reconstruction [75] (blue curve) was subtracted from the data. The time-series data visualized in this figure have been bandpassed between 30 Hz and 2 kHz so that the detector’s sensitive band is emphasized. The gravitational-wave strain amplitude of GW170817 is of the order of 10 ⁻²², and so is not visible in the bottom panel. [emphasis added]

It is apparent from these statements that considerable manipulation of the data was required to get the published results. From all the above issues, it seems that the initially quoted comment has some justification, and the claimed discovery by LIGO of gravitational waves from a neutron binary star merger may be questioned. Perhaps the observations may only be a supernova.