Search for transient gamma-ray emission from magnetar flares using Fermi-LAT

TL;DR

This study searches for transient gamma-ray emissions associated with magnetar flares using Fermi-LAT data, finding no significant signals except a marginal one near the galactic plane, possibly due to background contamination.

Contribution

First comprehensive search for gamma-ray transients coincident with magnetar flares in the 0.1-10 GeV range using Fermi-LAT data, with detailed analysis of multiple flares and time windows.

Findings

No significant gamma-ray emission detected from 14 of 15 flares.

Possible gamma-ray flare observed from magnetar 1E 1048.1-5937 with 4.4σ significance.

The detected signal may be contaminated by diffuse galactic background.

Abstract

We search for transient gamma-ray emission in the energy range from 0.1-10 GeV using data from the Fermi-LAT telescope in coincidence with magnetar flares. For our analysis, we look for coincidence with 15 distinct flares from 11 magnetars using three time windows of $\pm$ 1 day, $\pm$ 7 days, and $\pm$ 15 days. For 14 of these flares from 10 magnetars, we do not see any statistically significant gamma-ray emission. However, we see one possible gamma-ray flare from one magnetar, namely 1E 1048.1-5937, with combined significance of $4.4\sigma$, (after considering the look-elsewhere effect) observed after about 10 days from the start of the X-ray flare. However, this magnetar is located close to the galactic plane (with galactic latitude of -0.52\degree), and this signal could be caused by contamination due to diffuse flux from gamma-ray sources in the galactic plane.