THE K-BAND PERIOD LUMINOSITY RELATION FOR SEMIREGULAR PULSATING RED SUPERGIANTS IN THE MILKY-WAY AND IN M-33

A double-mode infrared-period-luminosity relation has been discovered for pulsating red supergiants (SRC type variables) in the Milky Way: M K(1)=-10.10-3.44 (log P-2.7) and M(K(2)) =-9.56-3.44(log P-2.7). Estim ates of the distance moduli have been derived for the Large Magellanic Cloud (DM(LMC)=18.28+/-0.09) and for the galaxy M 33 (DM(M33)=24.24+/ -0.09), based on the distance modulus adopted for the Per OBI stellar association (DM(Per OB1)=11.4). The ratio of the period of pulsation i n the first overtone to the period of the fundamental has been estimat ed for pulsating red supergiants; the same value (P1/P0)=0.704-0.04, h as been obtained for the Milky Way and M 33.