LIGO Inspiral Events Confirmation
The LIGO system was designed to detect binary inspiral events.
All the claims should have some form of confirmation. Currently only one detection has a claimed confirmation which includes a controversy.
LIGO '[looks] for inspiral signals, which can occur when two compact objects, such as neutron stars or black holes, form binary systems. Over time, the objects spiral in toward one another, producing gravitational radiation.
LIGO gravitational wave detectors saw a grand total of 11 events that have now been classified as robust gravitational wave detections.
As of September 26, 2019 all 41 LIGO events were within 6 days of an earth tide event (a crust uplift by the Sun or Moon).
Only the 11 robust events have an identified binary for a gravitational wave detection (GW event). The other 30 were assigned a probability of being a possible binary merger.
Of those 11 GW events, 9 were within 2 days of an earth tide event.
All 11 were within 6 days of an earth tide event.
Data are from Wikipedia.
The X day is the number of days from an earth tide event, like a Full Moon or New Moon.
GW150914 _ BH-BH _1 day FM
GW151012 _ BH-BH _ 0 day NM
GW151226 _ BH-BH _1 day FM
GW170104 _ BH-BH _0 day Perihelion
GW170608 _ BH-BH _1 day FM
GW170729 _ BH-BH _6 day NM
GW170809 _ BH-BH _2 day FM
GW170814 _ BH-BH _4 day Perigee
GW170817 _ NS-NS _1 day Perigee
GW170818 _ BH-BH _0 day Perigee
GW170823 _ BH-BH _2 day NM
Details about these celestial events are in separate topic.
The other LIGO events are just candidates with probabilities.
S190408 _ likely BH-BH
S190421 _ 96% chance of BH-BH
S190425 _ likely NS-NS
S190426c _ 49% chance of NS-NS; an initial news story called this a BH-NS
S190503bf _ 96% BH-BH, <1% BH-NS
S190510g _ 58% chance noise, no proposed merger
S190512at _ likely BH-BH
S190513bm _ likely BH-BH
S190517h _ likely BH-BH, <1% BH-NS
S190519bj _ likely BH-BH
S190521g _ likely BH-BH
S190521r _ likely BH-BH
S190602aq _ likely BH-BH
S190630ag _ likely BH-BH
S190701br _ likely BH-BH
S190706ai _ likely BH-BH
S190707q _ likely BH-BH
S190814bv _ likely BH-NS
S190720a _ likely BH-BH, 1% chance noise
S190727h _ likely BH-BH
S190728q _ 34% BH-BH,14% BH-NS
S190828j _ 1% BH-BH
S190828l _ likely BH-BH
S190901ap _ 86% NS-NS
S190910d _ likely BH-NS
S190910h _ 61% NS-NS, 39% noise
S190915ak _ likely BH-BH
S190923y _ no defined binary
S190924h _ MassGap event
likely is > 90% chance
One robust NS-NS Merger
GW170817 was a claimed NS-NS merger.
Note: there is a link below to a story about the controversy for this GW event.
These [NS-NS] events are believed to create short gamma-ray bursts.
GRB coincident with gravitational wave event GW150914
Fermi reported that its GBM instrument detected a weak gamma-ray burst above 50 keV, starting 0.4 seconds after the LIGO event and with a positional uncertainty region overlapping that of the LIGO observation. The Fermi team calculated the odds of such an event being the result of a coincidence or noise at 0.22%. However, observations from the INTEGRAL telescope's all-sky SPI-ACS instrument indicated that any energy emission in gamma-rays and hard X-rays from the event was less than one millionth of the energy emitted as gravitational waves, concluding that "this limit excludes the possibility that the event is associated with substantial gamma-ray radiation, directed towards the observer." If the signal observed by the Fermi GBM was associated with GW150914, SPI-ACS would have detected it with a significance of 15 sigma above the background. The AGILE space telescope also did not detect a gamma-ray counterpart of the event. A follow-up analysis of the Fermi report by an independent group, released in June 2016, purported to identify statistical flaws in the initial analysis, concluding that the observation was consistent with a statistical fluctuation or an Earth albedo transient on a 1-second timescale. A rebuttal of this follow-up analysis, however, pointed out that the independent group misrepresented the analysis of the original Fermi GBM Team paper and therefore misconstrued the results of the original analysis. The rebuttal reaffirmed that the false coincidence probability is calculated empirically and is not refuted by the independent analysis.
GW150914 is not publicized as having an independent confirmation with a GRB because the GW150914 event was claimed by LIGO to be a BH-BH merger which should not have generated a gamma ray burst. Therefore the GRB must be a coincidence not confirmation.
The historic GW170817 detection along with a GRB detection was claimed to validate LIGO.
GW 170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy NGC 4993. The GW was produced by the last minutes of two neutron stars spiralling closer to each other and finally merging, and is the first GW observation which has been confirmed by non-gravitational means. Unlike the five previous GW detections, which were of merging black holes not expected to produce a detectable electromagnetic signal, the aftermath of this merger was also seen by 70 observatories on 7 continents and in space, across the electromagnetic spectrum, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW 170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
The gravitational wave signal, designated GW 170817, had a duration of approximately 100 seconds, and shows the characteristics in intensity and frequency expected of the inspiral of two neutron stars. Analysis of the slight variation in arrival time of the GW at the three detector locations (two LIGO and one Virgo) yielded an approximate angular direction to the source. Independently, a short (~2 seconds' duration) gamma-ray burst, designated GRB 170817A, was detected by the Fermi and INTEGRAL spacecraft beginning 1.7 seconds after the GW merger signal. These detectors have very limited directional sensitivity, but indicated a large area of the sky which overlapped the gravitational wave position. It has been a long-standing hypothesis that short gamma-ray bursts are caused by neutron star mergers.
An intense observing campaign then took place to search for the expected emission at optical wavelengths. An astronomical transient designated AT 2017gfo (originally, SSS 17a) was found, 11 hours after the gravitational wave signal, in the galaxy NGC 4993 during a search of the region indicated by the GW detection. It was observed by numerous telescopes, from radio to X-ray wavelengths, over the following days and weeks, and was shown to be a fast-moving, rapidly-cooling cloud of neutron-rich material, as expected of debris ejected from a neutron-star merger.
On 17 August 2017, Fermi Gamma-Ray Burst Monitor software detected, classified, and localized a gamma-ray burst which was later designated as GRB 170817A. Six minutes later, a single detector at Hanford LIGO registered a gravitational-wave candidate which was consistent with a binary neutron star merger, occurring 2 seconds before the GRB 170817A event. This observation was "the first joint detection of gravitational and electromagnetic radiation from a single source".
Fermi GRBM detects GRB 170817A.
6 minutes later LIGO registers GW170817 which, from the LIGO analysis, occurred 2 seconds before GRB.
In 2019 a news story from Germany revealed the Fermi detection was first and then the LIGO report matched that Fermi observation, with LIGO only a few hours later.
This is the opposite sequence reported, including when LIGO received the Nobel Prize in 2017.
Online there are lists of known neutron stars for Z-ray pulsars and known X-ray point sources assumed to be black holes.
Another possible method of checking the LIGO claim is review the galaxy where the merger event was claimed to occur: Check that area for all the known X-ray point sources. Either a neutron star or black hole is claimed to be the source of those X-rays. There must be at least one of either present for a merger event to occur.
When LIGO reports a merger these source lists could be referenced. There is no thorough effort to make sure a detection involved known objects.
The LIGO system is passive, just reporting ripples. The best test is find the 2 objects before they merge to confirm all the details of the detection. That is not done. We do not have maps of the universe with this detail but gathering that data would help validate this system. Without any extra information LIGO just reports detections, as if to tell everyone the system is still on and just 'doing its thing' of looking for a template in the noise, as designed.
All of the other GW events with identified binaries were claimed to be BH-BH mergers.
Black hole mergers are assumed to leave no trace because the black hole is expected to clear the scene and so it will be the one remaining object.
This type of inspiral event is impossible to confirm.
When LIGO claims to have detected an event it should provide confirmation of that event. None have confirmation, except for the single NS-NS event.
With NO confirmations of the 10 BH-BH mergers and a likely confirmation of the 1 NS-NS merger, we just accept all events as valid.
If the software had a defect where an 'unexpected' signal was a match for the BH-BH template we would never know of that error because a claim for a BH-BH merger cannot be confirmed to determine whether the claim was correct or an error.
The certainty for all claimed GW events is not justified.
After finding a 2017 news story from Germany all of the above analysis might be irrelevant. A number of scientists have doubted the LIGO claims for that historic merger detection that validated LIGO.
I posted about that news story on September 11, 2019.
Here is the Thunderbolts Project view on GW.
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Added July 2019
Last updated (09/26/2019)
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