Radiative cooling of a shocked gas is evaluated for the case of a cold atmosphere of o Cet variable star type. Theoretical fluxes in Balmer and Paschen series of hydrogen and in HeI lines HeIλ4471 and HeIλ10830 are calculated. The difference between atom-ion and electron temperatures behind the shock front is taken into account. The most important elementary processes are included into consideration, such as non-stationary occupation of discrete and continuous hydrogen and helium levels by electron impact and radiative processes in blackbody field of the stellar radiation. The line scattering is calculated in the Biberman-Holstein-Sobolev model. The theoretical Balmer decrement is sensitive to undisturbed gas density. The HeI lines is more than one order of magnitude lower than that of Paschen series and Hγ at low initial shock velocity (50 km/s) and gas concentration of 10^{12} ÷ 10^{13} cm−3. At higher values of shock wave velocity (70 km/s) HeIλ10830 becomes comparable with ones of Paschen lines.
95.30.Ky Atomic and molecular data, spectra, and spectral parameters
$^1$Physics Department, M.V. Lomonosov Moscow State University, chair of Astrophysics and Stellar Astronomy.\
$^2$Physics Department, M.V. Lomonosov Moscow State University, chair of Experimental Astronomy.\
$^3$MSU, Sternberg astronomical institute
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