Searches for Radio Pulsars & Fast Transients and Multiwavelength Studies of Single-pulse Emission

Abstract

Pulsars are excellent tools for studying a wide array of astrophysical phenomena (e.g. gravitational waves, the interstellar medium, general relativity), yet they are still not fully understood. What are their emission processes and how do they change at different energies? How is giant pulse emission different from regular emission? How are different classes of pulsars (RRATs, magnetars, nulling pulsars, etc.) related? Answering these questions will not only help us to understand pulsars in general, but will also help improve techniques for pulsar searches and timing, gravitational wave searches, and single-pulse searches. The work we present here aims to answer these questions through studies of giant pulse emission, the discovery of new pulsars, and single-pulse studies of a large population of pulsars and RRATs. We took advantage of open telescope time on the 43-m telescope in Green Bank, WV to conduct a long-term study of giant pulses from the Crab pulsar at 1.2 GHz and 330 MHz. Over a timespan of 15 months, we collected a total of 95000 giant pulses which we correlated with both γ-ray photons from the Fermi satellite and giant pulses collected at 8.9 GHz. Statistics of these pulses show that their amplitudes follow power-law distributions, with indices in the range of 2.1 to 3.1. The correlation with giant pulses at 8.9 GHz showed that the emission processes at 1.2 GHz and 8.9 GHz are related, despite significant profile differences. The correlation with Fermi γ-ray photons was to test if increased pair production in the magnetosphere was the cause of giant pulses. Our findings suggest that, while it may play a role, increased pair production is not the dominant cause of giant pulses. As part of a single-pulse study, we reprocessed the archival Parkes Multibeam Pulsar Survey, discovering six previously unknown pulsars. PSR J0922−52 has a period of 9.68 ms and a DM of 122.4 pc cm −3. PSR J1147−66 has a period of 3.72 ms and a DM of 133.8 pc cm −3. PSR J1227−6208 has a period of 34.53 ms, a DM of 362.6 pc cm −3 , is in a 6.7 day binary orbit. PSR J1546−59 has a period of 7.80 ms and a DM of 168.3 pc cm −3. PSR J1725−3853 is an isolated 4.79-ms pulsar with a DM of 158.2 pc cm −3. PSR J1753−2822 has a period of 18.62 ms, a DM of 298.4 pc cm −3 , and is in a 9.3 hour binary orbit. These pulsars were likely missed in earlier processing efforts due to the fact that they have both high DMs and short periods, and also the large number of candidates that needed to be looked through. These discoveries suggest that further pulsars are awaiting discovery in the multibeam survey data.