摘要
Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation.In particular,we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars[G.Revet et al.,Sci.Adv.3,e1700982(2017)].The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments.We demonstrate that we can infer the formation of a plasma shell,surrounding the accretion column at the location of impact with the stellar surface,and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object.In our experiments,the accretion column ismodeled by having a collimated narrow(1 mm diameter)plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle,mimicking the high-density region of the stellar chromosphere.A combined approach using steady-state and quasi-stationarymodels was successfully applied tomeasure the parameters of the plasma all along its propagation,at the impact site,and in the structure surrounding the impact region.The formation of a hot plasma shell,surrounding the denser and colder core,formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy.
基金
X-ray data measurement,modeling and analysis were made by the JIHT RAS team with financial support from the Russian Science Foundation(Project No.17-72-20272)
The authors thank the entire staff of the ELFIE laser facility at LULI for their support during the experimental preparation and execution.This work was supported by ANR Blanc Grant No.12-BS09-025-01 SILAMPA and has received funding from the European Union’s Horizon 2020 research and innovation program through the European Research Council(ERC,Grant Agreement No.787539)
Some work was done within the LABEX Plas@Par project,which is supported by Grant No.11-IDEX-0004-02 from Agence Nationale de la Recherche.The research leading to these results is supported by Extreme Light Infrastructure Nuclear Physics(ELI-NP)Phase I,a project co-financed by the Romanian Government and European Union through the European Regional Development Fund.This work was performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under Contract No.DE-AC52-07NA27344.
