How is the redshift of gravitational wave events measured?

In summary, LIGO reported an event with a redshift of 0.6 < z < 1.3, but no electromagnetic radiation was detected. There is uncertainty about how the redshift was determined, but it is believed that the pre-merger, chirp, and ring-down frequencies were accurately measured. Various methods are available for determining the redshift of gravitational waves. One paper (Messenger et. al) discusses this in detail, and notes that the range of redshifts and masses is broad due to the degeneracy between redshift and mass. However, if an independent measurement of the redshift was available, the mass could potentially be determined with greater accuracy.
  • #1
Jorrie
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LIGO reported the announced event with a redshift of 0.6 < z < 1.3. With no em radiation event reported
(AFAIK), does anyone know how they have determined the redshift?
I understand how they could measure the pre-merger, chirp and ring-down frequencies with good accuracy. In order to determine redshift one must also know the emitted frequency. What methods are available for GWs?

PS: I have found one paper so far (2014, Messenger et. al): http://journals.aps.org/prx/pdf/10.1103/PhysRevX.4.041004
 
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  • #2
This is in Section VI of their paper. PRL 116, 061102 (2016)
 
  • #3
You may have noticed that the range of redshifts is really broad. Same with the range of masses. This is because the redshift is pretty highly degenerate with the masses of the two black holes. But it isn't perfectly degenerate.

Basically they slapped the whole model together and fit it to observations, and showed that the observations only fit within a limited range of redshift and mass.

If we had an independent measurement of the redshift of the merger, the mass could probably have been nailed down to much greater accuracy.
 

FAQ: How is the redshift of gravitational wave events measured?

1. What is redshift and how is it measured?

Redshift is a phenomenon in which light or other electromagnetic radiation from an object is shifted to longer wavelengths as the object moves away from an observer. It is measured by comparing the observed wavelength of a known spectral line from the object to its expected wavelength in a laboratory setting.

2. What is the significance of redshift in the measurement of gravitational waves?

Redshift plays a crucial role in measuring gravitational waves because it allows us to determine the distance to the source of the waves. By measuring the redshift, we can calculate the expansion of the universe and the distance the gravitational waves have traveled, providing important information about their source.

3. How is redshift used to determine the properties of the source of gravitational waves?

The redshift of an object can be used to determine its velocity, which can in turn provide information about its mass and energy. Additionally, the redshift can be used to determine the distance to the source, which is essential for understanding the properties of the source of gravitational waves.

4. Can redshift measurements of gravitational waves be affected by other factors?

Yes, redshift measurements can be affected by several factors, including the motion of the source, the presence of intervening matter, and the gravitational lensing effect. These factors must be accounted for in order to accurately measure the redshift of gravitational waves.

5. How does the redshift measurement of gravitational waves contribute to our understanding of the universe?

The redshift measurement of gravitational waves provides important information about the expansion of the universe, the properties of the source of the waves, and the nature of gravity itself. It also allows us to test and refine our theories about the universe and its evolution.

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