Using RXTE we found that during such flashes the X-ray intensity can oscillate at very high frequency. An example of this behavior is shown in the image below. The lower panel shows the X- ray intensity during the burst. The oscillations show up as the red, blue, and white region, and in this object the oscillation frequency is about 330 Hz. Using these data we have found evidence that the observed frequency represents the rate at which the neutron star spins.
Neutron stars are the fastest spinning stars known.
Studying the properties of X-ray bursts and the oscillations which occur during them allows us to obtain exciting new information about the properties of neutron stars. If you are interested in more details, you can follow the links below to several papers which explain the properties of oscillations during X-ray bursts. Here is a paper which reports the discovery of a neutron star near the Galactic center with 589 Hz oscillations during bursts, the 589 Hz burster . Here is a paper which describes the stability of the oscillation frequency in bursts from the same source over several years, the long-term stability of burst oscillations . This paper describes how strong the oscillations in bursts can be, the amplitudes of burst oscillations .