Cepheid Variables in M33 and the Extragalactic Distance Scale

Abstract

The DIRECT project aims to improve the extragalactic distance ladder by discovering Cepheids and eclipsing binaries in M31 and M33. We present the detection of Cepheids and other variables in M33 based on data obtained by the project over three observing seasons (Fall 1996 through Fall 1998).

We analyzed the data obtained by the project for fields "C" and "Y3", which were centered on the same coordinates and imaged with two cameras at Whipple Observatory. Since this region of the galaxy was imaged over three continuous seasons, we were able to search for long-period variables in addition to Cepheids. Data analysis was performed using both PSF-based photometry and difference image analysis, then compared to previous variable searches in this region of M33.

We present a preliminary Period-Luminosity relation for the Cepheids and light curves of some of the interesting long-period variables.