Abstract
We characterized the broad-band X-ray spectra of Swift J1745-26 during the decay of the 2013 outburst using INTEGRAL ISGRI, JEM-X and Swift XRT. The X-ray evolution is compared to the evolution in optical and radio. We fit the X-ray spectra with phenomenological and Comptonization models.We discuss possible scenarios for the physical origin of an ~50 d flare observed both in optical and X-rays ~170 d after the peak of the outburst.We conclude that it is a result of enhanced mass accretion in response to an earlier heating event.We characterized the evolution in the hard-X-ray band and showed that for the joint ISGRI-XRT fits, the e-folding energy decreased from 350 to 130 keV, while the energy where the exponential cut-off starts increased from 75 to 112 keV as the decay progressed. We investigated the claim that highenergy cut-offs disappear with the compact jet turning on during outburst decays, and showed that spectra taken with HEXTE on RXTE provide insufficient quality to characterize cut-offs during the decay for typical hard-X-ray fluxes. Long INTEGRAL monitoring observations are required to understand the relation between the compact jet formation and hard-X-ray behaviour. We found that for the entire decay (including the flare), the X-ray spectra are consistent with thermal Comptonization, but a jet synchrotron origin cannot be ruled out.
Original language | English (US) |
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Pages (from-to) | 1288-1298 |
Number of pages | 11 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 445 |
Issue number | 2 |
DOIs | |
State | Published - Dec 1 2014 |
Keywords
- Stars: black holes
- Stars: individual: Swift J174510.8-2624
- X-rays: binaries
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science