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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Variation of mass supply rate from the companion can be smeared out byviscous processes inside an accretion disk. By the time the flow reaches theinner edge, the variation in X-rays needs not reflect the true variation of therate at the outer edge. However, if the viscosity fluctuates around a meanvalue, one would expect the viscous time scale also to spread around a meanvalue. In HMXBs, the size of the viscous Keplerian disk is smaller & thus sucha spread could be lower as compared to the LMXBs. If there is an increasing ordecreasing trend in viscosity, the interval between enhanced emission would bemodified systematically. In the absence of a full knowledge about the variationof mass supply rates at the outer edge, we study ideal circumstances wheremodulation must take place exactly in orbital time scales when there is anellipticity in the orbit. We study a few compact binaries using long termRXTE/ASM(1.5-12 keV) & Swift/BAT(15-50keV) data to look for such effects & toinfer what these results can tell us about the viscous processes inside therespective disks. We employ three different methods to seek imprints ofperiodicity on the X-ray variation & found that in all the cases, the locationof the peak in the power density spectra is consistent with the orbitalfrequencies. Interestingly, in HMXBs the peaks are sharp with high rms values,consistent with a small Keplerian disk in a wind fed system. However, in LMXBswith larger Keplerian disk, the peaks are spread out with much lower rmsvalues. X-ray reflections, or superhump phenomena which may also cause suchX-ray modulations would not be affected by the size of the Keplerian disk. Ourresult confirms different sizes of Keplerian disks in 2 classes of binaries. Ifthe orbital period of a binary system is not known, it may be obtained withreasonable accuracy for HMXBs & with lesser accuracy for LMXBs by our method.

Smearing of mass accretion rate variation by viscous processes in accretion disks in compact binary systems