Searches for Fast Radio Bursts

Following the discovery of fast radio bursts (FRBs) in 2007, astronomers have entered a new era in astronomy in which understanding the nature of these type of radio transients is one of the most important modern astronomy questions. In this thesis I detail our current state of knowledge in this rapidly evolving field and describe real-time search systems designed to find FRBs using the 20-meter radio telescope at the Green Bank Observatory and the Arecibo L-band Feed Array (ALFA) receiver of the Arecibo 300-meter telescope in Puerto Rico. These experiments are called GBTrans and ALFABURST, respectively. I give details of the observing systems and report on the non-detection of FRBs for both surveys. GBTrans is sensitive enough to detect approximately half of all currently known FRBs while ALFABURST is sensitive enough to detect almost all of the current FRB population. I estimate that GBTrans survey probed redshifts out to about 0.3 corresponding to an effective survey volume of around 124,000 Mpc3. Assuming a constant density for sources per unit co-moving volume and considering the possibility of detecting bright FRBs in the sidelobes of the ALFA beams, I estimate ALFABURST probed redshifts out to about 3.5. Based on this, the expected event rate would be at most two FRBs per year at the 99% confidence level. Modeling the FRB rate as a function of fluence, F, as a power law with Fα, I constrain the index α \u3c 2.5 at the 90% confidence level based on the GBTrans results. A number of pulses from previously known pulsars were detected in both the GBTrans and ALFABURST surveys which provided excellent verification on the survey sensitivity used to compute the effective volumes quoted above. One Galactic transient, J1845+00, was found in the ALFABURST survey. This is most likely a member of the rotating radio transient (RRAT) population. It has so far not been seen in follow-up observations. Eight further single-pulse candidates from ALFABURST are also reported. At the time of writing, due to incomplete metadata records, the positions of these sources are not well enough known to allow further follow-up. Future observations with ALFABURST are anticipated in the coming year. Finally, I also describe preliminary observations from an Arecibo survey of gamma-ray burst sources

GBTrans: A commensal search for radio pulses with the Green Bank twenty metre telescope

We describe GBTrans, a real-time search system designed to find fast radio bursts (FRBs) using the 20-m radio telescope at the Green Bank Observatory. The telescope has been part of the Skynet educational program since 2015. We give details of the observing system and report on the non-detection of FRBs from a total observing time of 503 days. Single pulses from four known pulsars were detected as part of the commensal observing. The system is sensitive enough to detect approximately half of all currently known FRBs and we estimate that our survey probed redshifts out to about 0.3 corresponding to an effective survey volume of around 124,000~Mpc$^3$. Modeling the FRB rate as a function of fluence, $F$, as a power law with $F^{-\alpha}$, we constrain the index $\alpha < 2.5$ at the 90% confidence level. We discuss the implications of this result in the context of constraints from other FRB surveys.Comment: 7 pages, 6 figure