Discovery of high-frequency quasi-periodic oscillation in short-duration gamma-ray bursts

TL;DR

This study reports the detection of high-frequency quasi-periodic oscillations in three short gamma-ray bursts, suggesting the presence of hypermassive magnetars as central engines post binary neutron star mergers.

Contribution

First systematic identification of high-frequency QPOs in short GRBs, indicating magnetar central engines and providing new observational evidence.

Findings

QPOs detected at frequencies of 1258, 623, and 1410 Hz.

QPO signals have confidence levels above 5.2 sigma.

Results support the magnetar central engine model for short GRBs.

Abstract

Rapidly rotating newborn magnetars, which originate from binary neutron star (NS) mergers and serve as the central engines of short gamma-ray bursts (GRBs), may leave some imprints on their prompt gamma-ray light curves even though they are far from their radiating fireballs. A high-frequency quasi-periodic oscillation (QPO) would be a unique feature for the magnetar central engine, especially a hypermassive magnetar. By conducting a systematic analysis of the prompt gamma-ray light curves from 605 short GRBs observed by {\em Fermi}/Gamma-ray Burst Monitor, we have identified such QPO signals in three GRBs (e.g. GRB 120323A, GRB 181222B, and GRB 190606A). The QPOs that peaked at $1258^{+6}_{-6}$ Hz for GRB 120323A, $623^{+4}_{-4}$ Hz for GRB 181222B, and $1410^{+4}_{-5}$ Hz for GRB 190606A are all with a confidence level above 5.2 $\sigma$. The high-frequency QPO signals of those three short GRBs may be caused by a hypermassive magnetar acting as the central engine in a binary NS merger of a binary NS.