Concise Spectrotemporal Studies of Magnetar SGR J1935+2154 Bursts

Abstract

SGR J1935+2154 has truly been the most prolific magnetar over the last decade: It has been entering into burst active episodes once every 1-2 years since its discovery in 2014, it emitted the first Galactic fast radio burst associated with an X-ray burst in 2020, and has emitted hundreds of energetic short bursts. Here, we present the time-resolved spectral analysis of 51 bright bursts from SGR J1935+2154. Unlike conventional time-resolved X-ray spectroscopic studies in the literature, we follow a two-step approach to probe true spectral evolution. For each burst, we first extract spectral information from overlapping time segments, fit them with three continuum models, and employ a machine learning based clustering algorithm to identify time segments that provide the largest spectral variations during each burst. We then extract spectra from those non-overlapping (clustered) time segments and fit them again with the three models: the cutoff power-law model, the sum of two blackbody functions, and the model considering the emission of a modified black body undergoing resonant cyclotron scattering, which is applied systematically at this scale for the first time. Our novel technique allowed us to establish the genuine spectral evolution of magnetar bursts. We discuss the implications of our results and compare their collective behavior with the average burst properties of other magnetars.

Accepted for publication in ApJ

References in corpus (10)

• Fast Radio Bursts
• INTEGRAL discovery of a burst with associated radio emission from the magnetar SGR 1935+2154
• On the use of C-stat in testing models for X-ray spectra
• Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
• A Swift gaze into the 2006 March 29th burst forest of SGR 1900+14
• Resonant Compton Upscattering in Anomalous X-ray Pulsars
• Detailed high-energy characteristics of AXP 4U 0142+61 - Multi-year observations with INTEGRAL, RXTE, XMM-Newton and ASCA
• The game of life on a magnetar crust: from $\gamma$-ray flares to FRBs
• Fermi-GBM Observations of the SGR J1935+2154 Burst Forest
• Intensity and Polarization Characteristics of Extended Neutron Star Surface Regions

Cited by in corpus (2)

• Investigating the Recursive Short X-ray Burst Behavior of Magnetars Through Crustal Interactions
• Correlation of Burst Behaviour with Magnetar Age