Discovery of two new Fast X-ray Transients with INTEGRAL: IGR J03346+4414 and IGR J20344+3913

TL;DR

This paper reports the discovery of two new Fast X-ray Transients with INTEGRAL, characterized by brief, intense hard X-ray activity, and discusses their spectral and temporal properties to infer their nature.

Contribution

The paper presents the first identification of two new FXTs from archival INTEGRAL data, expanding knowledge of transient high-energy phenomena.

Findings

Both FXTs show short duration (15-30 min) hard X-ray activity above 20 keV.

Peak fluxes are approximately 10^-9 erg cm^-2 s^-1.

No soft X-ray counterparts detected in follow-up observations.

Abstract

We report on the discovery of two Fast X-ray Transients (FXTs) from analysis of archival INTEGRAL data. Both are characterized by a remarkable hard X-ray activity above 20 keV, in term of duration (about 15 and 30 minutes, respectively), peak-flux (about 10^-9 erg cm^-2 s^-1) and dynamic range (about 2400 and 1360, respectively). Swift/XRT follow-up observations failed to detect any quiescent or low level soft X-ray emission from either of the two FXTs, providing an upper limit of the order of a few times 10^-12 erg cm^-2 s^-1. The main spectral and temporal IBIS/ISGRI characteristics are presented and discussed with the aim of infering possible hints on their nature.