An Arecibo Search for Fast Radio Transients from M87

TL;DR

This study used the Arecibo telescope to search for fast radio bursts from M87, setting the most stringent upper limits to date and finding no evidence of such bursts, which constrains models of neutron star activity in the galaxy.

Contribution

First dedicated search for fast radio transients from M87 with Arecibo, providing the most stringent upper limits on burst rate and informing models of neutron star populations.

Findings

No astrophysical bursts detected above 7σ threshold.

Upper limit on burst rate is less than 0.1 bursts per hour.

Results are consistent with giant pulse emission from young neutron stars.

Abstract

The possible origin of millisecond bursts from the giant elliptical galaxy M87 has been scrutinized since the earliest searches for extragalactic fast radio transients undertaken in the late 1970s. Motivated by rapid technological advancements in recent years, we conducted $\rm \simeq 10~hours$ of L-band ($\rm 1.15-1.75~GHz$) observations of the core of M87 with the Arecibo radio telescope in 2019. Adopting a matched filtering approach, we searched our data for single pulses using trial dispersion measures up to $\rm 5500~pc~cm^{-3}$ and burst durations between $\rm 0.3-123~ms$. We find no evidence of astrophysical bursts in our data above a 7$\sigma$ detection threshold. Our observations thus constrain the burst rate from M87 to $\rm \lesssim 0.1~bursts~hr^{-1}$ above $\rm 1.4~Jy~ms$, the most stringent upper limit obtained to date. Our non-detection of radio bursts is consistent with expectations of giant pulse emission from a Crab-like young neutron star population in M87. However, the dense, strongly magnetized interstellar medium surrounding the central $\sim 10^9 \ M_{\odot}$ supermassive black hole of M87 may potentially harbor magnetars that can emit detectable radio bursts during their flaring states.