Night sky

Contact information

Vivien Raymond

Tel: +44 (0)29 2087 4458

School of Physics and Astronomy

Cardiff University

The Parade

CF24 3AA, Cardiff, Wales, UK

Research Snapshots


Figure 6 from "GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run"

There are now many objects in the gravitational-wave sky ! Figure 6 of GWTC2 shows the credible region contours for all candidate events in the plane of total mass M and mass ratio q. Each contour represents the 90% credible region for a different event.

Research Snapshots


V. Raymond, for the LIGO-Virgo collaboration

With the second oberving run from the advanced detector network LIGO-Virgo our knowledge of the population(s) of binary black hole keeps increasing. The individual observations are described in LIGO/Virgo Phys. Rev. X 6, 041015, Phys. Rev. Lett. 118, 221101 (2017), Phys. Rev. Lett. 119, 141101 (2017), ApJL 851, 2 (2017).


"The fascination of gravitational waves" is a 5-minute clip from Deutsche Welle's Tomorrow Today that I participated in: "Gravitational waves were detected on 14 September 2015, more than a century after they were first proposed. Astrophysicist Vivien Raymond hopes the historic discovery will help provide answers to some of the biggest questions in science." (english version).


The first joint observation from gravitational waves and electro-magnetic waves! A world-wide, multimessenger effort localized the source of the GW170817 signal in space and time.


V. Raymond, for the LIGO-Virgo collaboration

The first observing run of the advanced detector era delivered three noteworthy observations: GW150914, GW151226 and the (less significant) LIGO-Virgo Trigger LVT151012. The LIGO Open Science Center provides the tools to see how well gravitational-waves from General Relativity match the data.

PRL cover

LIGO Scientific Collaboration and Virgo Collaboration

On September 14, 2015 at 09:50:45 UTC the two LIGO detectors observed a transient gravitational-wave signal ! GW150914 was generated 1.3+0.5-0.6 billions light-years away with the merger of two black-holes of 36+5-4M and 29+4-4M into a 62+4-4M black hole, radiating 3+0.5-0.5Mc2 in gravitational waves.


Wave examples

V. Raymond, for the LIGO-Virgo collaboration

Different sources create different signals: here are three examples of gravitational-wave signals from different types of inspiraling binary systems: First, the red signal comes from a system of two black holes of mass 10M and 5M that are not spinning. Second, the green signal is for black holes with the same masses, but now with each of the two components spinning. Finally, the blue signal comes from a system of two neutron stars each with mass equal to 1.4M, which aren't spinning. Read the complete science summary here.

Wave examples noise

V. Raymond, for the LIGO-Virgo collaboration

Noise in the detector: here the actual data from the detector is shown in gray. The noise is much louder than the expected signals in red, green and blue (from the figure above, superimposed on the gray noise signal).


V. Raymond, M. van der Sluys, V. Kalogera

This is a video of our Markov-Chain Monte Carlo (MCMC) algorithm trying to home in on the Probability Density Function (PDF) of the parameters of a LIGO compact binary coalescence software injection. Here only the marginalized PDF for the chirpmass (M=(M1*M2)(3/5)(M1+M2)(-1/5)) is shown. Each color on the two bottom plots represents an independent chain and gives the corresponding value of chirpmass and likelihood (natural logarithm) as a function of iteration number.

Pisa seminar

V. Raymond

Thanks to the people at the INFN in Pisa, my presentation for the Stefano Braccini Prize was recorded. Click on the picture for the 572 MB, 40 min video.