Studies of luminous stars in nearby galaxies. VII - The brightest blue stars in the spiral galaxies M101 and NGC 2403

The first spectra of individual stars outside our own Local Group of galaxies have been obtained for suspected supergiants in the fields of Ml0l and NGC 2403. Four stars in NGC 2403 and three in Ml0l are confirmed to be members. The visually brightest stars in both galaxies are A-type supergiants, and their spectral characteristics are consistent with the luminosities derived from their membership in M 101 and NGC 2403. The visual luminosities of the A-type supergiants are - 9.4 mag for the one in NGC 2403 and -10.3 mag and -10.1 mag for the two in Ml0l. These two supergiants in M 101 are the visually brightest normal stars yet known in any galaxy.