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

There have been many efforts to explain the dynamical mechanisms behind thephenomenology of quasi-periodic oscillations (QPOs) seen in the X-ray lightcurves of low-mass X-ray binaries. Up to now, none of the models cansuccessfully explain all the frequencies observed in the power density spectrumof the light curve. Here we perform several hydrodynamic simulations ofnon-self-gravitating relativistic axisymmetric thick tori applied to theneutron star in the low-mass X-ray binary 4U 1636-53 and show how the observedoscillation modes triggered by different velocity perturbations give rise to aset of variability features similar to what we see in the observational X-raydata. When we match pairs of frequencies from the simulations of constantangular momentum ($l$) tori with the observed kilo Hertz QPOs, we find thatcertain combinations of frequencies lie on top of the observed relation,provided we assume a smaller mass for the neutron star than is generallyassumed. However, constant-$l$ tori cannot match the entire range offrequencies observed for 4U 1636-53 due to physical constraints set by thetorus size. We show that our model is consistent with the observed shift in QPOfrequency that accompany state transitions of the accretion disk.

The kilo Hertz quasi-periodic oscillations in neutron star low-mass X-ray binaries as tori oscillation modes. I