Cepheids in M31 - The PAndromeda Cepheid sample

TL;DR

This paper presents the largest and most homogeneous sample of Cepheids in M31 from the Pan-STARRS1 survey, improving period-luminosity relations and confirming a broken slope previously observed with HST data.

Contribution

It introduces an unbiased, homogeneous method for identifying Cepheids in M31 using Fourier parameters and color cuts, expanding the known sample significantly.

Findings

2686 Cepheids identified, including various types.

Period-Luminosity relations with smaller dispersions.

Confirmation of a broken slope in the PL relation.

Abstract

We present the largest Cepheid sample in M31 based on the complete Pan-STARRS1 survey of Andromeda (PAndromeda) in the $r_{\mathrm{P1}}$ , $i_{\mathrm{P1}}$ and $g_{\mathrm{P1}}$ bands. We find 2686 Cepheids with 1662 fundamental mode Cepheids, 307 first-overtone Cepheids, 278 type II Cepheids and 439 Cepheids with undetermined Cepheid type. Using the method developed by Kodric et al. (2013) we identify Cepheids by using a three dimensional parameter space of Fourier parameters of the Cepheid light curves combined with a color cut and other selection criteria. This is an unbiased approach to identify Cepheids and results in a homogeneous Cepheid sample. The Period-Luminosity relations obtained for our sample have smaller dispersions than in our previous work. We find a broken slope that we previously observed with HST data in Kodric et al. (2015), albeit with a lower significance.