The Swift Supergiant Fast X-ray Transients Project: a review, new results, and future perspectives

TL;DR

This paper reviews the SFXT project, highlighting how Swift observations have expanded data on supergiant fast X-ray transients, enabling detailed spectral analysis, duty cycle assessment, and new observational insights into their outbursts.

Contribution

It introduces a systematic Swift-based approach to study SFXTs, significantly increasing data and understanding of their properties and behaviors.

Findings

Tripled the available broad-band data of SFXT outbursts

Provided detailed spectral characterization of SFXTs

Demonstrated Swift's capability to monitor bright flares panchromatically

Abstract

We present a review of the Supergiant Fast X-ray Transients (SFXT) Project, a systematic investigation of the properties of SFXTs with a strategy that combines Swift monitoring programs with outburst follow-up observations. This strategy has quickly tripled the available sets of broad-band data of SFXT outbursts, and gathered a wealth of out-of-outburst data, which have led us to a broad-band spectral characterization, an assessment of the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present some new observational results obtained through our outburst follow-ups, as fitting examples of the exceptional capabilities of Swift in catching bright flares and monitor them panchromatically.