Poster Presentation

Template Light Curves of Cepheid Variables Based on PS1 PAndromeda Data

I-Ling, Lin (NCU), Chow-Choong, Ngeow (NCU)

Cepheid Variables are standard candles that can be used to obtain distances to nearby galaxies using their well-calibrated period-luminosity relations. In opposite to BVI photometric system, characteristics of Cepheids are not well studied in grizy filters. Hence we initiated a project to study Cepheids in Pan-STARRS 1 (PS1) grizy photometric system. However, light curves data for Cepheids are sparsely populated in PS1. Therefore, we developed a template light curves approach to derive mean magnitudes of Cepheids in PS1 data.

The development of templates is as follow. We started to query r and i observed data for 1440 known FM Cepheids in M31 from PAndromeda catalog (Kodric et al., 2012 [AJ 145:106]) and reproduce the phased light curves using the Fourier decomposition technique. Then we subtracted the mean magnitude from catalog for each light curve and divided their amplitudes to obtain the normalized light curves. We also shifted the folded light curves such that phase zero corresponding to maximum brightness. Criterion based on correlation coefficient was applied to compare, or distinguish, the shapes of two light curves. These light curves with similar shape were stacked together to generate template light curves. Here we present our template light curves in r and i band for M31 FM Cepheids .