# A Multi-telescope Campaign on FRB 121102: Implications for the FRB Population

## TL;DR

This study reports the first subarcsecond localization of FRB 121102 through a coordinated multi-telescope campaign, revealing complex burst spectra, intrinsic structural variations, and estimating the FRB population's birth rate based on repeated bursts.

## Contribution

It provides the first simultaneous multi-telescope detection and localization of an FRB, analyzes burst spectral and structural properties, and estimates the FRB source birth rate.

## Key findings

- Burst spectra have a ~500 MHz envelope, not well modeled by a power law.
- Detected radio energies up to 10^40 erg.
- Estimated FRB source birth rate consistent with young pulsar or magnetar models.

## Abstract

We present results of the coordinated observing campaign that made the first subarcsecond localization of a Fast Radio Burst, FRB 121102. During this campaign, we made the first simultaneous detection of an FRB burst by multiple telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Of the nine bursts detected by the Very Large Array at 3 GHz, four had simultaneous observing coverage at other observatories. We use multi-observatory constraints and modeling of bursts seen only at 3 GHz to confirm earlier results showing that burst spectra are not well modeled by a power law. We find that burst spectra are characterized by a ~500 MHz envelope and apparent radio energy as high as $10^{40}$ erg. We measure significant changes in the apparent dispersion between bursts that can be attributed to frequency-dependent profiles or some other intrinsic burst structure that adds a systematic error to the estimate of DM by up to 1%. We use FRB 121102 as a prototype of the FRB class to estimate a volumetric birth rate of FRB sources $R_{FRB} \approx 5x10^{-5}/N_r$ Mpc$^{-3}$ yr$^{-1}$, where $N_r$ is the number of bursts per source over its lifetime. This rate is broadly consistent with models of FRBs from young pulsars or magnetars born in superluminous supernovae or long gamma-ray bursts, if the typical FRB repeats on the order of thousands of times during its lifetime.