XMM-Newton view of a hard X-ray transient IGR J17497-2821

TL;DR

This paper analyzes XMM-Newton observations of the transient IGR J17497-2821, revealing its spectral and timing properties indicative of a hard state with a truncated accretion disk and energy-dependent variability.

Contribution

It provides detailed spectral and timing analysis of IGR J17497-2821 during its outburst, highlighting its hard state characteristics and energy-dependent variability.

Findings

Spectral fit with hard powerlaw and weak disk blackbody

Detection of broad iron K-alpha line from truncated disk

Energy-dependent rms variability increasing with energy

Abstract

We present spectral and energy dependent timing characteristics of the hard X-ray transient IGR J17497-2821 based on XMM-Newton observations performed five and nine days after its outburst on 2006 September 17. We find that the source spectra can be well described by a hard (Gamma ~ 1.50) powerlaw and a weak multicolour disk blackbody with inner disk temperature kT_{in} ~ 0.2 KeV. A broad iron K - alpha line with FWHM ~ 27000 Km/s, consistent with that arising from an accretion disk truncated at large radius, was also detected. The power density spectra of IGR J17497 - 2821, derived from the high resolution (30 micro second) timing mode XMM-Newton observations, are characterised by broadband noise components that are well modelled by three Lorentzians. The shallow power law slope, low disk luminosity and the shape of the broadband power density spectrum indicate that the source was in the hard state. The rms variability in the softer energy bands (0.3-2 KeV) found to be ~ 1.3 times that in 2-5 and 5-10 KeV energy bands. We also present the energy dependent timing analysis of the RXTE/PCA data, where we find that at higher energies, the rms variability increases with energy.