Searching for post-glitch signals from pulsars with gravitational wave detectors

Abstract

[eng] Pulsars are neutron stars–remnants of very massive stars– that emit intense electromagnetic radiation and rotate at great speed. Depending on their position and axis of rotation, we can detect this radiation from Earth and catalogue a huge number of these stellar objects. As a consequence of various factors, pulsars may suffer spontaneous increases in their rotation frequency, even though they tend to lose energy over time: this phenomenon is what we know as glitches. It has been widely theorized that glitches make pulsars act as gravitational waves emitters. With the help of the LIGO and VIRGO detectors, essential for detecting gravitational waves in the past, we aspire to detect the disturbances in space-time produced in this case by the mentioned pulsars, never detected before. These are a particular kind of gravitational waves known as transient continuous waves, because they are fainter and more durable than the waves generated in the merger of two compact objects, already detected, but not lasting as long as truly continuous waves. Specifically, we are looking for signals with duration between hours and months, coming from pulsars that suffered one or more glitches during the Advanced LIGO and Virgo O3 period (between April 2019 and March 2020). Using electromagnetic ephemerides to have a good estimation of the gravitational wave signal we expect to detect, we will perform a “narrow-band” search: the sky position of the pulsar is fixed, but we allow some uncertainty on the values of the frequency and its derivatives. We will work with a search pipeline using the F-statistic and the Bstatistic. The process will go through some preparation steps, mainly to select suitable targets for our purposes and cleaning the Short Fourier Transforms previously generated for each of the detectors. Using the statistics we will search for relevant points in a template bank formed by the parameters of our search and, if there are no significant outliers, then we will use simulated signal injections to derive upper limits, a test to see at which GW strain we are capable of actually detecting some signal from each target. Finally, we also want to study the possibility of making more and better detections in the future. On the one hand, analyzing improvements in current detectors, and on the other, thinking about the new detectors that will be available in the next decade. This work is part of an international, more exhaustive, project with a journal publication, planned to be out in the next months.