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

AK~Sco stands out among pre-main sequence binaries because of its prominentultraviolet excess, the high eccentricity of its orbit and the strong tidesdriven by it. AK Sco consists of two F5 type stars that get as close as 11R$_*$at periastron passage. The presence of a dense  ($n_e \sim 10^{11}$~cm$^{-3}$) extended envelope has been unveiled recently.In this article, we report the results from a XMM-Newton based monitoring ofthe system. We show that at periastron, X-ray and UV fluxes are enhanced  by a factor of $\sim 3$ with respect to the apastron values. The X-rayradiation is produced in an optically thin plasma with T$\sim 6.4\times 10^{6}$K and it is found that the N$_H$ column density rises from 0.35$\times10^{21}$~cm$^{-2}$ at periastron to 1.11$\times 10^{21}$~cm$^{-2}$ at apastron,in good agreement with previous polarimetric observations. The UV emissiondetected in the Optical Monitor band seems to be caused by the reprocessing ofthe high energy magnetospheric radiation on the circumstellar material.  Further evidence of the strong magnetospheric disturbances is provided by thedetection of line broadening of 278.7~km~s$^{-1}$ in the N~V line withHST/STIS.  Numerical simulations of the mass flow from the circumbinary disk to thecomponents have been carried out. They provide a consistent scenario with whichto interpret AK~Sco observations. We show that the eccentric orbit acts like agravitational piston. At apastron, matter is dragged efficiently from the innerdisk border, filling the inner gap and producing accretion streams that end asring-like structures around each component of the system. At periastron, thering-like structures come into contact, leading to angular momentum loss, andthus producing an accretion outburst.

XMM-Newton monitoring of the close pre-main-sequence binary AK Sco. Evidence of tide driven filling of the inner gap in the circumbinary disk