Freeze-Out Effects in Hydrogen and Helium Lines of SN 1987A at the Early Photospheric Epoch

Abstract.

We have developed a time-dependent model of ionization, excitation and energy balance of the atmosphere of SN 1987A at the photospheric epoch to study early behavior of hydrogen and helium lines. The ionization freeze-out effects play a key role in producing both the strong H$\alpha$ during nearly the first month and the He I 5876 Å scattering line on day 1.76. Using an extended reaction network between hydrogen molecules and their ions demonstrates that ion-molecular processes are likely responsible for the blue peak in the H${\alpha}$ profile at the Bochum event epoch.