We present the results of a new search for variable stars in the Local Group ( LG ) isolated dwarf galaxy IC 1613 , based on 24 orbits of F475W and F814W photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope .
We detected 259 candidate variables in this field , of which only 13 ( all of them bright Cepheids ) were previously known .
Out of the confirmed variables , we found 90 RR Lyrae stars , 49 classical Cepheids ( including 36 new discoveries ) , and 38 eclipsing binary stars for which we could determine a period .
The RR Lyrae include 61 fundamental ( RR ab ) and 24 first-overtone ( RR c ) pulsators , and 5 pulsating in both modes simultaneously ( RR d ) .
As for the majority of LG dwarfs , the mean periods of the RR ab and RR c ( 0.611 and 0.334 day , respectively ) as well as the fraction of overtone pulsators ( f _ { c } =0.28 ) place this galaxy in the intermediate regime between the Oosterhoff types .
From their position on the period-luminosity diagram and light-curve morphology , we can unambiguously classify 25 and 14 Cepheids as fundamental and first-overtone mode pulsators , respectively .
Another two are clearly second-overtone Cepheids , the first ones to be discovered beyond the Magellanic Clouds .
Among the remaining candidate variables , five were classified as \delta -Scuti and five as long-period variables .
Most of the others are located on the main-sequence , the majority of them likely eclipsing binary systems , although some present variations similar to pulsating stars .
We estimate the distance to IC 1613 using various methods based on the photometric and pulsational properties of the Cepheids and RR Lyrae stars .
The values we find are in very good agreement with each other and with previous estimates based on independent methods .
When corrected to a common reddening of E ( B - V ) =0.025 and true LMC distance modulus of ( m - M ) _ { LMC, 0 } =18.515 \pm 0.085 , we find that all the distance determinations from the literature converge to a common value of ( m - M ) _ { 0 } =24.400 \pm 0.014 ( statistical ) , or 760 kpc .
The parallel WFPC2 field , which lies within three core radii , was also searched for variable stars .
We discovered nine RR Lyrae stars ( 4 RR ab , 4 RR c and 1 RR d ) and two Cepheids , even though the lower signal-to-noise ratio of the observations did not allow us to measure their periods as accurately as for the variables in the ACS field-of-view .
We provide their coordinates and approximate properties for completeness .