Free–free absorption parameters of Cassiopeia A from low-frequency interferometric observations

Context. Cassiopeia A is one of the most extensively studied supernova remnants (SNRs) in our Galaxy. The analysis its continuum spectrum through low-frequency observations plays an important role for understanding evolution radio source and propagation synchrotron emission to observers SNR environment ionized interstellar medium. Aims. In this paper we present measurements integrated Cas characterize properties free–free absorption toward SNR. We also add new track slowly evolving decreasing flux density. Methods. used Giant Ukrainian Radio Telescope (GURT) measure within frequency range 16–72 MHz. density relative reference galaxy Cygnus was measured May–October 2019 with two subarrays GURT, as a two-element correlation interferometer. Results. determine magnitudes measure, electron temperature, average number charges ions both internal external absorbing gas A. Generally, their values are comparable, albeit slight differences, recently presented values. absence clumping, find that unshocked ejecta M = 2.61 ⊙ at 15.3 cm −3 has temperature T ≈ 100 K. If clumping factor 0.67, then 0.96 18.7 . Conclusions. obtained GURT interferometric consistent theoretical model measurement errors reasonably other recent results literature.