| Abstract | Infrared photometry of long-period variables in M 33 shows that the majority of those identified up to now are supergiants. The tip of the asymptotic giant branch may also be visible, but the present data are not adequate to decide the matter. Calibration photometry presented here confirms that the distance of M 33 is 890 kpc with an uncertainty of approximately 15 percent. The Cepheid and supergiant period-luminosity relations are in satisfactory agreement on this point. |
