UsingXMM–Newtonto study the energy-dependent variability of H 1743-322 during its 2014 outburst

Abstract

Black hole transients during bright outbursts show distinct changes of their spectral and variability properties as they evolve during an outburst, that are interpreted as evidence for changes in the accretion flow and X-ray emitting regions. We obtained an anticipated XMMNewton ToO observation of H 1743-322 during its outburst in September 2014. Based on data of eight outbursts observed in the last 10 years we expected to catch the start of the hardto-soft state transition. The fact that neither the general shape of the observed power density spectrum nor the characteristic frequency show an energy dependence implies that the source still stays in the low-hard state at the time of our observation near outburst peak. The spectral properties agree with the source being in the low-hard state and a Swift/XRT monitoring of the outburst reveals that H 1743-322 stays in the low-hard state during the entire outburst (a. k. a. 'failed outburst'). We derive the averaged QPO waveform and obtain phase-resolved spectra. Comparing the phase-resolved spectra to the phase averaged energy spectrum reveals spectral pivoting. We compare variability on long and short time scales using covariance spectra and find that the covariance ratio does not show an increase towards lower energies as has been found in other black hole X-ray binaries. There are two possible explanations: either the absence of additional disc variability on longer time scales is related to the rather high inclination of H 1743-322 compared to other black hole X-ray binaries or it is the reason why we observe H 1743-322 during a failed outburst. More data on failed outbursts and on high-inclination sources will be needed to investigate these two possibilities further.

The Reverberation Lag in the Low-Mass X-Ray Binary H1743-322

“…The best-fit galactic column density is N H ∼ 2 × 10 22 cm −2 , consistent with values reported in the literature (e.g. Stiele & Yu 2016;Shidatsu et al 2014), though slightly higher than derived from galactic HI surveys (N H ∼ 7 × 10 21 cm −2 , e.g. Dickey & Lockman 1990), thus suggesting local absorption.…”

“…The PSD shows band limited broad band noise and type C quasi periodic oscillations (QPO, the main harmonic being detected at ν ∼ 0.2 Hz) during all the observations. These are all features typical of the hard state and were reported also by Stiele & Yu (2016) for O4. The characteristic frequencies appear constant among all the observations (including O1), besides a slight increase (a factor ∼1.15) of the frequencies of the QPO and of the high frequency break during O3 and O4.…”

“…In the hardness-intensity diagram of the source (e.g. Dunn et al 2010) these values are typical of the hard state, as also shown by Stiele & Yu (2016) for O4. In Table 2 we also report the total 3-10 keV flux (F 3−10 keV ) of the source.…”

“…XMM-Newton has recently re-observed it three times, during the 2014 outburst. Both the 2008 and 2014 are "failed outbursts" (Capitanio et al 2009;Stiele & Yu 2016), meaning that the source did not reach the transition to the soft state and remained in the hard state for the entire outburst. In this paper we report on the study of all the available XMM-Newton observations of H1743-322 during outburst.…”

Phase-resolved spectral analysis of the 11 mHz quasi-periodic oscillation in the black hole candidate H1743–322

“…Because the PCA instrument is not sensitive below 3 keV, the hydrogen column density could not be well constrained using our data. Different values of NH have been previously reported for this source: NH = 1.35×10 22 cm −2 , NH = 2.01×10 22 cm −2 (Stiele & Yu 2016) and NH = 2.2 × 10 22 cm −2 (McClintock et al 2009). Prat et al (2009) used 1.8 ×10 22 cm −2 , which they determined from Swift and XMM-Newton observations.…”