# A 21 cm pilot survey for pulsars and transients using the Focal L-Band Array for the Green Bank Telescope

## TL;DR

This paper presents a pilot survey using the FLAG receiver at the Green Bank Telescope to search for pulsars and fast radio bursts, demonstrating the instrument's capabilities and setting upper limits on FRB rates.

## Contribution

It introduces the use of the FLAG phased array feed for pulsar and FRB surveys, showing improved sensitivity and potential for higher pulsar detection rates.

## Key findings

- No new sources detected in the survey.
- Upper limit on FRB rate above 0.36 Jy ms is 1.3 x 10^6 per day per sky.
- FLAG can find 2-3 times more pulsars than single pixel receivers.

## Abstract

Phased Array Feed (PAF) receivers are at the forefront of modern day radio astronomy. PAFs are currently being developed for spectral line and radio continuum surveys and to search for pulsars and fast radio bursts. Here, we present results of the pilot survey for pulsars and fast radio bursts using the Focal plane L-band Array for the Green Bank Telescope (FLAG) receiver operating in the frequency range of 1.3--1.5 GHz. With a system temperature of $\sim$18 K, the receiver provided unprecedented sensitivity to the survey over an instantaneous field of view (FoV) of 0.1 deg$^{2}$. For the survey, we implemented both time and frequency domain search pipelines designed to find pulsars and fast radio bursts that were validated by test pulsar observations. Although no new sources were found, we were able to demonstrate the capability of this instrument from observations of known pulsars. We report an upper limit on the rate of fast radio bursts above a fluence of 0.36~Jy ms to be 1.3 $\times$ 10$^6$ events per day per sky. Using population simulations, we show that the FLAG will find a factor of 2--3 more pulsars in same survey duration compared to its single pixel counterpart at the Green Bank Telescope. We also demonstrate that the new phased array receiver, ALPACA for the Arecibo telescope, will be a superior survey instrument and will find pulsars at a higher rate than most contemporary receivers by a factor of 2--10.