Fourier‐resolved Spectroscopy of 4U 1543−47 during the 2002 Outburst

Abstract

We have obtained Fourier-resolved spectra of the black hole binary 4U 1543-47 in the canonical states (high/soft, very high, intermediate, and low/hard) observed in this source during the decay of an outburst that took place in 2002. Our objective is to investigate the variability of the spectral components generally used to describe the energy spectra of black hole systems, namely a disk component, a power-law component attributed to Comptonization by a hot corona, and the contribution of the iron line due to reprocessing of the high-energy (E k 7 keV ) radiation. We find that (1) the disk component is not variable on timescales shorter than $100 s, (2) the reprocessing emission as manifest by the variability of the Fe K line responds to the primary radiation variations down to timescales of $70 ms in the high and very high states, but longer than 2 s in the low state, (3) the low-frequency QPOs are associated with variations of the X-ray power-law spectral component and not to the disk component, and (4) the spectra corresponding to the highest Fourier frequency are the hardest (show the flatter spectra) at a given spectral state. These results question models that explain the observed power spectra as due to modulations of the accretion rate alone, as such models do not provide any apparent reason for a Fourier frequency dependence of the power-law spectral indices.

Fourier‐Resolved Spectroscopy of 4U 1728‐34: New Insights into Spectral and Temporal Properties of Low‐Mass X‐Ray Binaries

“…This result agrees with those found in other neutron star ( Revnivtsev & Gilfanov 2006) and black hole (Reig et al 2006) binaries.…”

“…Therefore, through FRS we can investigate whether different spectral components in the overall spectrum of the source (e.g., blackbody, Comptonization, iron line) are variable and at which frequency. In general, the interpretation of the FRS is not unique (see Papadakis et al 2005;Reig et al 2006 for some insights). For spectral features that result from the reprocessing of higher energy (E !…”

“…It has been pointed out that this method is particularly suited for the study of spectral features that result from X-ray reprocessing, where the light crossing time provides a natural frequency filter; in this case FRS can provide straightforward insights about the geometry of the reprocessing medium. So far, this technique has been applied successfully to Galactic black hole candidates ( Revnivtsev et al 1999;Gilfanov et al 2003;Sobolewska & Zycki 2006;Reig et al 2006), to neutron star LMXBs (Gilfanov & Revnivtsev 2005), and also to active galactic nuclei (AGNs; Papadakis et al 2005Papadakis et al , 2006, yielding insights into variability of different spectral components and infer their spatial arrangements.…”

Fourier‐Resolved Spectroscopy of Active Galactic Nuclei UsingXMM‐NewtonData. I. The 3–10 keV Band Results

“…Recently, Arevalo et al (2006) suggested that Ark 564 operates like GBHs in their ''very high state.'' Since the relation between EW FRS and f norm is not known for systems in this state (the results of Reig et al 2006 suggest that EW FRS in VHS systems is smaller than in HS systems), we cannot make any conclusive statements at the moment.…”

“…Using the same approach, the X-ray continuum spectral variability of the Galactic black hole binaries (GBHs) GX 339-4 and 4U 1543À47, during its 2002 outburst, as well as Cyg X-1 in its soft state, have also been studied by Revnivtsev et al (2001), Reig et al (2006), and Gilfanov et al (2000), respectively. Fourierresolved spectroscopy ( FRS) has also been used to study the nature of the quasi-periodic oscillations in neutron stars (Gilfanov et al 2003;Gilfanov & Revnivtsev 2005;Sobolewska &Życki 2006).…”