Twenty-four thousand hours of GREENBURST observations with the GBT

TL;DR

GREENBURST utilized 24,186 hours of GBT data to detect pulsars and FRBs, including a new pulsar with high nulling fraction, highlighting challenges in single-beam FRB detection.

Contribution

First large-scale analysis of GREENBURST data revealing new pulsar and confirming known FRBs, emphasizing detection challenges with single-beam observations.

Findings

Detected 50 pulsars and 3 FRBs in extensive GBT data.

Discovered a new pulsar, PSR J0039+5407, with high nulling fraction.

Identified detection challenges due to single-beam limitations.

Abstract

In addition to fast radio burst (FRB) searches carried out using dedicated surveys, a number of radio observatories take advantage of commensal opportunities with large facilities in which observations for other projects can be searched for FRBs and other transient sources. We present the results from one such effort, the first 24,186 hours of the GREENBURST search for dispersed radio pulses with the Green Bank Telescope (GBT). To date, GREENBURST has detected a total of 50 pulsars and three FRBs. One of the pulsars, PSR J0039+5407, has a period of 2.2 s and was previously unknown. Using follow-up observations with the Canadian Hydrogen Intensity Mapping Experiment, we found a timing solution for this pulsar which shows it to have a characteristic age of 2 Myr. Additional GBT observations show the pulsar has a very high nulling fraction ($\sim70-80\%$). All three of the FRBs are repeating sources that were previously known and were being monitored by the GBT as part of other projects. A major challenge for GREENBURST in the discovery of new FRBs is its single beam. This makes it hard to distinguish some of the pulses from sources of radio frequency interference. We highlight this problem with a case study of an FRB-like pulse that initially passed our interference filters. Upon closer inspection, the event appears to be part of a longer-duration narrow-band source of unknown origin. Further observations and monitoring are required to determine whether it is terrestrial or celestial.