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Properties of accretion shocks in young stars: comparison between high energy observations and MHD models (S. Bonito - INAF/Palermo, IT)

We compare multi-band (X-rays and UV) observations with MHD models of accretion shocks, formed where the disk material accretes onto a young star and impacts its surface.
In our models we take into account the main physical effects: radiative cooling, thermal conduction, gravity, and a description of the stellar atmosphere.
We synthesize the spectral properties of the impact regions considering different inclinations of the system with respect to the line-of-sight, the local absorption due to the surrounding material, and the Doppler shift due to plasma motion along the line-of-sight.
The comparison between the synthetic spectra and the observations of star-disk systems (e.g. TWHya) allows us to investigate the luminosity and the profiles of several lines in the X-ray and UV bands, and also the Doppler shift and its observability.
The study of the high energy radiation emerging from the accretion shocks is fundamental to constrain heating and ionization of circumstellar material and disk lifetime.
The future X-ray mission Athena will allow for analysis of a consistent statistical sample of young accreting stars, thus an exploration of the influence of different environments and conditions on the physics of accreting plasma in star-disk systems will be possible.


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