Accretion shock stability on a dynamically heated YSO atmosphere with radiative transfer

¹ Laboratoire AIM, CEA/DSM - CNRS - Université Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
² LERMA, Observatoire de Paris, Université Pierre et Marie Curie, ENS, Université de Cergy Pontoise and CNRS, 5 Place J. Janssen, 92195 Meudon, France
³ CEA, IRAMIS, Service Photons, Atomes et Molécules, 91191 Gif-sur-Yvette, France
⁴ Laboratoire Lagrange, Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 06304 Nice cedex 4, France
⁵ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721

^a e-mail: lionel.de-sa@cea.fr
^b e-mail: jean-pierre.chieze@cea.fr
^c e-mail: chantal.stehle@obspm.fr
^d e-mail: titos.matsakos@cea.fr
^e e-mail: laurent.ibgui@obspm.fr
^f e-mail: thierry.lanz@oca.eu
^g e-mail: hubeny@as.arizona.edu

Published online: 8 January 2014

Abstract

Theory and simulations predict Quasi-Periodic Oscillations of shocks which develop in magnetically driven accretion funnels connecting the stellar disc to the photosphere of Young Stellar Objects (YSO). X-ray observations however do not show evidence of the expected periodicity.

We examine here, in a first attempt, the influence of radiative transfer on the evolution of material impinging on a dynamically heated stellar atmosphere, using the 1D ALE-RHD code ASTROLABE. The mechanical shock heating mechanism of the chromosphere only slightly perturbs the flow. We also show that, since the impacting flow, and especially the part which penetrates into the chromosphere, is not treated as a purely radiating transparent medium, a sufficiently efficient coupling between gas and radiation may affect or even suppress the oscillations of the shocked column.

This study shows the importance of the description of the radiation effects in the hydrodynamics and of the accuracy of the opacities for an adequate modeling.