Searching for the Signature of Fast Radio Burst by Swift/XRT X-ray Afterglow Light Curve

TL;DR

This study investigates X-ray afterglow light curves of GRBs to find signatures of fast radio bursts, but finds no matching evidence, thus constraining possible FRB origins related to neutron star collapse.

Contribution

It introduces a method to analyze X-ray afterglows for FRB signatures and applies it to Swift/XRT data, providing new constraints on FRB progenitor models.

Findings

No X-ray afterglow signatures matching FRB onset were found.

The analysis constrains the timing and nature of potential neutron star collapse events.

Results suggest FRBs may not be directly associated with the specific X-ray afterglow features studied.

Abstract

A new type of cosmological transient, dubbed fast radio bursts (FRBs), was recently discovered. The source of FRBs is still unknown. One possible scenario of an FRB is the collapse of a spinning supra-massive neutron star. Zhang (2014) suggests that the collapse can happen shortly (hundreds to thousands of seconds) after the birth of supra-massive neutron stars. The signatures can be visible in X-ray afterglows of long and short gamma-ray bursts (GRBs). For instance, a sudden drop (decay index steeper than -3 to -9) from a shallow decay (decay index shallower than -1) in the X-ray afterglow flux can indicate the event. We selected the X-ray afterglow light curves with a steep decay after the shallow decay phase from the Swift/XRT GRB catalog. We analyzed when the decay index changed suddenly by fitting these light curves to double power-law functions and compared it with the onset of FRBs. We found none of our GRB samples match the onset of FRBs.