Quasi-Periodic Peak Energy Oscillations in X-ray Bursts from SGR J1935+2154

Abstract

Magnetars are young neutron stars powered by the strongest magnetic fields in the Universe (10${}^{13-15}$ G). Their transient X-ray emission usually manifests as short (a few hundred milliseconds), bright, energetic ($\sim$ 10${}^{40-41}$ erg) X-ray bursts. Since its discovery in 2014, magnetar J1935+2154 has become one of the most prolific magnetars, exhibiting very active bursting episodes, and other fascinating events such as pulse timing anti-glitches and Fast Radio Bursts. Here, we present evidence for possible 42 Hz (24 ms) quasi-periodic oscillations in the $\nu F_{\nu }$ spectrum peak energy (Ep) identified in a unique burst detected with the Fermi Gamma-ray Burst Monitor in January 2022. While quasi-periodic oscillations have been previously reported in the intensity of magnetar burst lightcurves, quasi-periodic oscillations in the Ep have not. We also find an additional event from the same outburst that appears to exhibit similar character in Ep, albeit of lower statistical quality. For these two exceptional transients, such Ep oscillations can be explained by magnetospheric density and pressure perturbations. For burst-emitting plasma consisting purely of $e^{+}{e}^{-}$ pairs, these acoustic modes propagate along a highly magnetized flux tube of length up to around $L\sim 130$ neutron star radii, with $L$ being lower if ions are present in the emission zone. Detailed time-resolved analyses of other magnetar bursts are encouraged to evaluate the rarity of these events and their underlying mechanisms.

References in corpus (21)

• A fast radio burst associated with a Galactic magnetar
• A bright millisecond-duration radio burst from a Galactic magnetar
• INTEGRAL discovery of a burst with associated radio emission from the magnetar SGR 1935+2154
• The Fourth Fermi-GBM Gamma-Ray Burst Catalog: A Decade of Data
• A peculiar hard X-ray counterpart of a Galactic fast radio burst
• On the theory of magnetar QPOs
• Detection of two bright radio bursts from magnetar SGR 1935+2154
• Resonant Compton Upscattering in Anomalous X-ray Pulsars
• Ground-based calibration and characterization of the Fermi Gamma-Ray Burst Monitor Detectors
• The NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154
• Rapid Spectral Variability of a Giant Flare from a Magnetar in NGC 253
• Fermi/GBM View of the 2019 and 2020 Burst Active Episodes of SGR J1935+2154
• Quasi-Periodic Oscillations in Short Recurring Bursts of the Soft-Gamma Repeater J1550-5418
• On the Distance of SGR 1935+2154 Associated with FRB 200428 and Hosted in SNR G57.2+0.8
• Quasi-Periodic Oscillations in Short Recurring Bursts of the magnetars SGR 1806-20 and SGR 1900+14 Observed With RXTE
• Quasi-periodic oscillations of the X-ray burst from the magnetar SGR J1935+2154 and associated with the fast radio burst FRB 200428
• Intermittency and Lifetime of the 625 Hz QPO in the 2004 Hyperflare from the Magnetar SGR 1806-20 as evidence for magnetic coupling between the crust and the core
• Fermi-GBM Observations of the SGR J1935+2154 Burst Forest
• Searching for quasi-periodic oscillations in astrophysical transients using Gaussian processes
• Pitfalls of periodograms: The non-stationarity bias in the analysis of quasi-periodic oscillations
• High-Energy Photon Opacity in the Twisted Magnetospheres of Magnetars

Cited by in corpus (2)

• Prospects for Time-Domain and Multi-Messenger Science with eXTP
• Nonlinear coupling between magnetar QPOs