Long-term Monitoring of Supergiant Fast X-ray Transients with Swift: From Hours to Years
Abstract
Supergiant Fast X-ray Transients (SFXTs) are HMXBs with OB supergiant companions and are known for hour-long X-ray outbursts characterized by 3-5 orders of magnitude luminosity increases. Our Swift Supergiant Fast X-ray Transients Project has investigated in the last few years both these bright flares and the emission outside the bright outbursts, where the high sensitivity of the X-Ray Telescope (XRT) can be best exploited. In particular, by taking advantage of Swift's flexible scheduling, we have been performing regular monitoring with the XRT of several SFXTs and candidates, with 2-3 observations per week (1-2 ks) for at least one year per source. This has allowed us to determine their long-term properties, and to obtain an assessment of the fraction of the time these sources spend in each luminosity phase (outbursts, intermediate level, and quiescence) and their duty cycle of inactivity by means of very sensitive and non-serendipitous observations. We present the most recent results from the 2011-2013 monitoring campaigns.
- Publication:
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AAS/High Energy Astrophysics Division #13
- Pub Date:
- April 2013
- Bibcode:
- 2013HEAD...1340202R