Optical and infrared flares from a transient Galactic soft gamma-ray repeater

TL;DR

This paper reports the discovery of optical and infrared flares from a transient galactic soft gamma-ray repeater, providing new insights into the multi-wavelength behavior of these rare neutron star systems.

Contribution

It presents the first detection of optical and near-infrared bursts from an SGR, linking transient X-ray emission to multi-wavelength flaring activity.

Findings

Over 40 optical flares observed over 3 days

Infrared flare detected 11 days after optical activity

Proposes a new subgroup of SGRs with transient X-ray emission

Abstract

Soft gamma-ray repeaters (SGRs) are a rare type of gamma-ray transient sources that are ocasionally detected as bursts in the high-energy sky. They are thought to be produced by magnetars, young neutron stars with very strong magnetic fields of the order of 10^(14-15) G. Only three such objects are known in our Galaxy, and a fourth one is associated with the supernova remnant N49 in the Large Magellanic Cloud. In none of these cases has an optical counterpart to either the gamma-ray flares or the quiescent source been identified. Here we present multi-wavelength observations of a puzzling source, SWIFT J195509+261406, for which we detected more than 40 flaring episodes in the optical band over a time span of 3 days, plus a faint infrared flare 11 days later, after which it returned to quiescence. We propose that SWIFT J195509+261406 is a member of a subgroup of SGRs for which the long-term X-ray emission is transient in nature. Furthermore, it is the first SGR for which bursts have been detected in the optical and near-infrared bands and maybe the link between the "persistent" SGRs and the dim isolated neutron stars.