Multiwavelength observations of the black hole transient Swift J1745−26 during the outburst decay
Year: 2014
Type: article
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 high-energy 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.
Institutions: Sabancı Üniversitesi, Middle East Technical University, Istanbul University, New York University Abu Dhabi, Instituto de Astrofísica de Canarias, Space Sciences Laboratory, University of California, Berkeley, Friedrich-Alexander-Universität Erlangen-Nürnberg, Max Planck Institute for Extraterrestrial Physics, European X-Ray Free-Electron Laser, European Space Astronomy Centre, International Space Science Institute, University of Southampton, Brera Astronomical Observatory, University of Cape Town, University of South Wales, Liverpool John Moores University, University of Oxford
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2108769171