Ionisation loss and shock excitation of 4420Са I and 4420Са II atoms in cold remnants of type II supernovae

Анотація

The light emission (“glow”) of cold dusty plasma of the remnant of SN 1987A was confirmed by the Hubble Space Telescope observations on 7th January,  1995. In  particular, Ca I and Ca II lines  were recorded and identified in the spectrum of the supernova’s envelope. The period of complete hydrogen recombination in the remnant is 800 days. Thus, it is only radioactive decay that could be a primary source of the plasma light emission at the moment of observation. This paper describes the conditions of shock excitation and recombination  of  ⁴⁴₂₀Ca resulted  from  the  decay  of  radioactive ⁴⁴₂₂Ti  travelling  in  the  remnant’s  cold  dust.  The  overionisation in  the  remnant  resulted from  the  motion  of the  ⁴⁴₂₀Ca recoil  nucleus,  as  well  as  its  impact  on  the spectrum  formation,  was  studied.  It  has  been  shown that the calcium lines are formed by the   ⁴⁴₂₀Ca II ion in the  inner  layers  of  the  remnant.  We  have  reached  the conclusion that the Ca I/Ca II line strength ratio corresponds to the isotopic abundance ratio [⁴⁴₂₀Ca] /[⁴⁴₂₀Ca] in Type II supernova remnants.