The cepheid period-luminosity relation (the Leavitt law) at mid-infrared wavelengths. IV. Cepheids in IC 1613

We present mid-infrared period-luminosity relations forCepheids in the Local Group galaxy IC 1613. Using archival Infrared Array Camera (IRAC) imaging data from Spitzer we were able to measure single-epoch magnitudes for five, 7-50 days, Cepheids at 3.6 and 4.5 μm. When fit to the calibrating relations,measured for the LargeMagellanic Cloud Cepheids, the data give apparent distance moduli of 24.29 ± 0.07 and 24.28 ± 0.07 at 3.6 and 4.5 μm, respectively. A multiwavelength fit to previously published BVRIJHK apparent moduli and the two IRAC moduli gives a true distance modulus of 24.27 ± 0.02 mag with E(B-V ) = 0.08 mag, and a corresponding metric distance of 715 kpc. Given that these results are based on single-phase observations derived from exposures having total integration times of only 1000 s pixel^-1, we suggest that Cepheids out to about 2 Mpc are accessible to Spitzer with modest integration times during its warm mission. We identify the main limiting factor to this method to be crowding/contamination induced by the ubiquitous population of infrared-bright asymptotic giant branch stars.