2022AstBu..77..301K

We present the results of observations within the program for the search for new highly magnetized white dwarfs among evolutionary old stars of this class. The program was carried out for two years at the 1-m telescope of the SAO RAS. As a result, new white dwarf candidates of different ages with super-strong (several megagauss, tens, hundreds of megagauss) magnetic fields were discovered. These observations, along with the observations of other authors made it possible to make a new estimate of the frequency of occurrence of magnetic white dwarfs among old stars. Our results confirm our earlier assumptions that the frequency of occurrence of far-evolved magnetic white dwarfs with magnetic fields of several megagauss or higher and with the temperatures of less than 10 000 K is at the level of 15% or higher, while the frequency of occurrence of such stars among young white dwarfs does not exceed 4-6%. This fact means that the thermal evolution of the physical properties of magnetic white dwarfs differs from the thermal evolution of their weakly magnetic counterparts.