Variables in NGC 3109 dwarf irregular galaxy

The periods range from about 430d to almost 1500d. Because of our relatively bright limiting magnitude, only 45 of the more than 400 known carbon stars were measured, but none was found to be a large amplitude variable.

One of the Miras may be an unrecognized C star. Five of the O-Miras are probably hot-bottom burning stars considering that they are brighter than expected from the period-luminosity relation of Miras and that, by comparison with theoretical evolutionary tracks, they appear to have masses >~4M_{sun}_. A census of very long period (P>1000d) Miras in the Galaxy and Magellanic Clouds is presented and discussed together with the newly discovered long-period, but relatively blue, variables in NGC3109.