The Color-Magnitude Diagram of the Globular Cluster M14

TL;DR

This study presents a detailed color-magnitude diagram of the globular cluster M14, highlighting differential reddening effects and the median magnitude of RR Lyrae stars using new observational data.

Contribution

First detailed CMD of M14 using recent R and V images, identifying RR Lyrae positions and analyzing reddening effects.

Findings

Identified 64 of 112 RR Lyrae stars on the CMD

Detected significant differential reddening across the cluster

Measured median RR Lyrae magnitude as V=17.2

Abstract

Using the SARA 0.9 meter telescope at Kitt Peak National Observatory (KPNO) we obtained R images during the summer of 2010 and V images during the summer of 2012 of the globular cluster M14. These images were analyzed using the DAOPHOT/ALLFRAME package of Stetson (1987,1994) to create a preliminary color-magnitude diagram (CMD) of M14. We have positively identified the positions of 64 of the 112 known RR Lyrae stars on the CMD. We find considerable spread in both the magnitudes and color of the RR Lyrae stars indicating a significant amount of differential reddening on relatively small scales. This is also seen in the giant branch which shows up to ~0.15 magnitude spread in V-R color. We also found the median magnitude of the RR Lyrae stars and hence the horizontal branch to be V=17.2.