English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We present a novel method for measuring the lags of (weak) variabilitycomponents in neutron-star and black-hole low-mass X-ray binaries (LMXBs). Forthis we assume that the power and cross spectra of these sources consists of anumber of components that are coherent in different energy bands, but areincoherent with one another. The technique is based on fitting simultaneouslythe power spectrum (PS) and the Real and Imaginary parts of the cross spectrum(CS) with a combination of Lorentzian functions. We show that, because the PSof LMXBs is insensitive to signals with a large Imaginary part and a small Realpart in the CS, this approach allows us to uncover new variability componentsthat are only detected in the CS. We also demonstrate that, contrary to earlierclaims, the frequency of the type-C quasi-periodic oscillation (QPO) in theblack-hole binary GRS 1915+105 does not depend on energy. Rather, the apparentenergy dependence of the QPO frequency can be explained by the presence of aseparate QPO component with a slightly higher frequency than that of the QPO,whose rms amplitude increases faster with energy than the rms amplitude of theQPO. From all the above we conclude that, as in the case of the PS, the CS ofblack-hole and neutron-star binaries can be fitted by a combination ofLorentzian components. Our findings provide evidence that thefrequency-dependent part of the transfer function of these systems can bedescribed by a combination of responses, each of them acting over relativelywell-defined time scales. This conclusion challenges models that assume thatthe main contribution to the lags comes from a global, broadband, transferfunction of the accreting system.

Unveiling hidden variability components in accreting X-ray binaries using both the Fourier power and cross spectra