Laboratory analogue of a supersonic accretion column in a binary star system

Abstract

Astrophysical flows exhibit rich behaviour resulting from the interplay of different forms of energy—gravitational, thermal, magnetic and radiative. For magnetic cataclysmic variable stars, material from a late, main sequence star is pulled onto a highly magnetized (B>10 MG) white dwarf. The magnetic field is sufficiently large to direct the flow as an accretion column onto the poles of the white dwarf, a star subclass known as AM Herculis. A stationary radiative shock is expected to form 100–1,000 km above the surface of the white dwarf, far too small to be resolved with current telescopes. Here we report the results of a laboratory experiment showing the evolution of a reverse shock when both ionization and radiative losses are important. We find that the stand-off position of the shock agrees with radiation hydrodynamic simulations and is consistent, when scaled to AM Herculis star systems, with theoretical predictions.

Laboratory unraveling of matter accretion in young stars

“…1A ). This setup differs in several notable ways from previous experiments focused on investigating radiative accretion shocks, where magnetic fields are totally absent (while the presence of the magnetic field is crucial in reproducing CTTSs observations in a realistic way), and in which the use of “shock tubes” ( 38 , 39 ) affects the dynamics of the constrained plasma.…”

Counter-propagating radiative shock experiments on the Orion laser and the formation of radiative precursors

“…By restricting the transverse width of the gas cell, the shocks act as quasi-one dimensional shocks and can interact with 'wall shocks' [15,18]. Many of these experiments focused on studying the radiative precursor [19,20,21,22,23,24,25] while modifications to this experimental configuration have allowed for the study of more complex phenomena, such as the formation of reverse radiative shocks [26] [27] [28] or collisions with obstacles [29,30].…”

Laser experiment for the study of accretion dynamics of Young Stellar Objects: Design and scaling

“…accretion flow generates a reverse shock in the incoming flow. Contrary to the shock-tube setup [5], the entire dynamics is here embedded in an external magnetic field, and the edge-free propagation of the flow allows specific plasma motion to freely develop at the border of the reverse shock, as demonstrated in Ref. [1].…”

“…Up to now, in the context of accretion shocks, experiments were used to model the impact of a plasma flow onto an obstacle using the so-called shock-tube setup as detailed for example by Cross et al [5]. This consists in creating a plasma expansion at the rear surface of a target irradiated on its front surface by a high power laser (I Laser ∼ 10 14 W cm −2 ).…”