# 28th Texas Symposium on Relativistic Astrophysics

13-18 December 2015
International Conference Centre Geneva
Europe/Zurich timezone

## Swift and the Supergiant Fast X-ray Transient outburst factory

14 Dec 2015, 16:15
25m
Level 0, Room 3 (International Conference Centre Geneva)

Talk

### Speaker

Patrizia Romano (INAF)

### Description

We present the results of the Swift Supergiant Fast X-ray Transients project, which has been exploiting *Swift*'s capabilities in a systematic study of SFXTs and classical supergiant X-ray binaries (SGXBs) since 2007. The unique combination of sensitivity and scheduling flexibility of *Swift*/XRT allowed us to perform an efficient long-term monitoring of 16 including both SFXTs and classical SGXBs. We followed source activity across more than 4 orders of magnitude in X-ray luminosity and sampled the light curves on timescales spanning from hours to years. Our measurements of dynamic ranges, duty cycles as a function of luminosity, and of luminosity distributions show systematic differences that help discriminate between different models of SFXTs/SGXBs, while our outburst follow-ups provide a steady advancement in the comprehension of the SFXT phenomenon. In particular, the observations of the SFXT prototype IGR J17544-2619 on 2014 October 10, when the source reached a peak luminosity of $3\times10^{38}$ erg s$^{-1}$, challenged, for the first time, the maximum theoretical luminosity achievable by a wind-fed neutron star high mass X-ray binary. We propose that this giant outburst was due to the formation of a transient accretion disc around the compact object.

### Co-authors

David Burrows (The Pennsylvania State University) Enrico Bozzo (ISDC) Hans Krimm (NASA Goddard Space Flight Center) Jamie A. Kennea (The Pennsylvania State University) Lorenzo Ducci (University of Tuebingen) Neil Gehrels (NASA Goddard Space Flight Center) Paolo Esposito (National Institute for Astrophysics - INAF) Phil Evans (University of Leicester) Scott Barthelmy (NASA Goddard Space Flight Center) Stefano Vercellone (INAF)

### Presentation Materials

 Homepage: The Swift SFXT Project romanop_sfxts_texas15_pub.pdf