Chasing candidate Supergiant Fast X-ray Transients in the 1,000 orbits INTEGRAL/IBIS catalog

TL;DR

This study identifies four new candidate Supergiant Fast X-ray Transients (SFXTs) by analyzing X-ray data from the INTEGRAL/IBIS catalog, significantly increasing the known sample of such objects and providing detailed multi-wavelength characterization.

Contribution

The paper presents the first detailed high-energy analysis of four poorly studied X-ray transients, proposing them as new SFXT candidates and expanding the known population.

Findings

Four new SFXT candidates identified.

Enhanced understanding of their X-ray properties.

Sample of candidate SFXTs doubled.

Abstract

We report results from an investigation at hard X-rays (above 18 keV) and soft X-rays (below 10 keV) of a sample of X-ray transients located on the Galactic plane and detected with the bursticity method, as reported in the latest 1,000 orbits INTEGRAL/IBIS catalog. Our main aim has been to individuate those with X-rays characteristics strongly resembling Supergiant Fast X-ray Transients (SFXTs). As a result, we found four unidentified fast X-ray transients which now can be considered good SFXT candidates. In particular, three transients (IGR J16374-5043, IGR J17375-3022 and IGR J12341-6143) were very poorly studied in the literature before the current work, and our findings largely improved the knowledge of their X-ray characteristics. The other transient (XTE J1829-098) was previously studied in detail only below 10 keV, conversely the current work provides the first detailed study in outburst above 18 keV. In addition we used archival infrared observations of the transients to pinpoint, among the field objects, their best candidate counterpart. We found that their photometric properties are compatible with an early type spectral classification, further supporting our proposed nature of SFXTs. Infrared spectroscopy is advised to confirm or disprove our interpretation. The reported findings allowed a significant increase of the sample of candidate SFXTs known to date, effectively doubling their number.