Spectral and Timing Properties of IGR J17091-3624 in the Rising Hard State During Its 2016 Outburst
Abstract
We present a spectral and timing study of the NuSTAR and Swift observations of IGR J17091-3624 in the hard state during its outburst in 2016. IGR J17091-3624 is a galactic black hole binary candidate that has been previously observed to display variability patterns similar to GRS 1915+105, despite the apparent faintness compared to its counterpart. Disk reflection features are clearly revealed in the NuSTAR data taken in three epochs. Fitting with relativistic reflection models reveals the accretion disk is truncated during all epochs and the modeling favors a low disk inclination. The source flux increased by ~50% during the observations, the steepening of the spectral continuum is accompanied by a declination in the high energy cut-off. A type-C QPO increasing in frequency is detected in the NuSTAR data. In addition, we find a secondary peak centered at about 2.3 times the fundamental QPO frequency in the power spectra. This unconventional frequency questions the harmonic origin of the feature. We investigate the evolution of the timing and spectral properties on the rising phase of the outburst and discuss its physical implications.
- Publication:
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AAS/High Energy Astrophysics Division #16
- Pub Date:
- August 2017
- Bibcode:
- 2017HEAD...1610916X