The structure of radiative shock waves

Free access article

Issue		A&A Volume 368, Number 3, March IV 2001


Page(s)		901 - 911
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20010064

A&A 368, 901-911 (2001)
DOI: 10.1051/0004-6361:20010064

III. The model grid for partially ionized hydrogen gas

Yu. A. Fadeyev¹ and D. Gillet²

¹ Institute for Astronomy of the Russian Academy of Scienewcommandes, Pyatnitskaya 48, 109017 Moscow, Russia
e-mail: fadeyev@inasan.rssi.ru
² Observatoire de Haute-Provenewcommande -CNRS, 04870 Saint-Michel l'Observatoire, Franewcommande
e-mail: gillet@obs-hp.fr

(Received 27 September 2000 / Accepted 19 December 2000 )

Abstract
The grid of the models of radiative shock waves propagating through partially ionized hydrogen gas with temperature $3000 \mathrm{K}\le T_1\le 8000 \mathrm{K}$ and density $10^{-12} {\rm gm} {\rm cm}^{-3}\le\rho_1\le 10^{-9} {\rm gm} {\rm cm}^{-3}$ is computed for shock velocities $20 {\rm km} {\rm s}^{-1}\le U_1\le 90 {\rm km} {\rm s}^{-1}$ . The fraction of the total energy of the shock wave irreversibly lost due to radiation flux ranges from 0.3 to 0.8 for $20 {\rm km} {\rm s}^{-1}\le U_1\le 70 {\rm km} {\rm s}^{-1}$ . The postshock gas is compressed mostly due to radiative cooling in the hydrogen recombination zone and final compression ratios are within $1 < \rho_N/\rho_1\la 10^2$ , depending mostly on the shock velocity U₁. The preshock gas temperature affects the shock wave structure due to the equilibrium ionization of the unperturbed hydrogen gas, sinewcommande the rates of postshock relaxation processes are very sensitive to the number density of hydrogen ions ahead the discontinuous jump. Both the inewcommandrease of the preshock gas temperature and the decrease of the preshock gas density lead to lower postshock compression ratios. The width of the shock wave decreases with inewcommandreasing upstream velocity while the postshock gas is still partially ionized and inewcommandreases as soon as the hydrogen is fully ionized. All shock wave models exhibit stronger upstream radiation flux emerging from the preshock outer boundary in comparison with downstream radiation flux emerging in the opposite direction from the postshock outer boundary. The differenewcommande between these fluxes depends on the shock velocity and ranges from 1% to 16% for $20 {\rm km} {\rm s}^{-1}\le U_1\le 60 {\rm km} {\rm s}^{-1}$ . The monochromatic radiation flux transported in hydrogen lines significantly exceeds the flux of the background continuum and all shock wave models demonstrate the hydrogen lines in emission.

Key words: shock waves -- hydrodynamics -- radiative transfer -- stellar atmospheres

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