Speaker
Claire Michaut
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.4009.pdf
Shock propagation through cepheid envelopes
O. Saincir1,2 , C. Michaut2 , L. Di Menza1,2 , S. Bouquet3,2 , M. Mancini2
1 Laboratoire de Mathématiques, Université de Reims, Moulin de la Housse, 51687 Reims,
France
2 LUTH, Observatoire de Paris, PSL Research University, CNRS, Université Paris Diderot,
Sorbonne Paris Cité, 92190 Meudon, France
3 CEA, DAM, DIF, 91297 Arpajon, France
A cepheid is a supergiant variable star which is positioned in the instability band of the HR
diagram. Spectroscopic and interferometric observations [1] show that long-period cepheids
exhibit asymmetries in the P Cygni-type profiles around the Hα line [2]: an absorption compo-
nent with an emission component redshifted or blueshifted depending on the pulsation phase.
Astronomers assume that these asymmetries are caused by the presence of strong shocks [3]
propagating in the envelope due to the pulsation of the photosphere [4].
The HADES code [5] is a numerical tool which is developed since several years to perform
numerical simulations of radiative hydrodynamics models for the study of hypersonic flows in
stellar physics (jets of young stars, accretion shocks, supernova remnants, etc.). The interest of
our work is to use HADES to carry out simulations of shock in the envelope of cepheids accord-
ing to the scenarios proposed by astronomers. In order to compare our numerical results with
observations, an observable around the Hα line is reconstructed from hydrodynamic quantities
resulting from numerical simulations (density, velocity and temperature of the fluid).
References
[1] P. Kervella, A. Mérand, A. Gallenne, Astron. & Astrophys. 498, 425 (2009)
[2] N. Nardetto, J.H. Groh, S. Kraus, et al., Astron. & Astrophys. 489, 1263 (2008)
[3] D. Gillet, A. B. Fokin, Astron. & Astrophys. 68, A72 (2014)
[4] A. Mérand, P. Kervella, V. Coudé du Foresto et al., Astron. & Astrophys. 453, 155 (2006)
[5] C. Michaut, L. Di Menza, H.C. Nguyen et al., High Energy Density Physics 22, 77 (2017)
