飯糰鬼的鬼地方

The Variable Stars on Globular Cluster M5

Yu-Lun Wu

The Department of Earth Sciences, NTNU

Introduction

　　M5 is a global cluster in Serpens, which is 24500 ly far away from earth. According to the past record of studies, there were more then 147 variables in it. Most of them were on the surface of the cluster, and because of their short period, they were easily to observe.

　　RR Lyre variables are almost founded in global clusters, their period are generally for a few hours. They are less mass and less metal stars, which means they are very old, might be as old as when our galaxy formed.

　　We are using M5 images to find variables in it. Trying to find what stars in M5 might be RR Lyre variables, and trying to describe these star’s period of light transform, or its light curve.

Observation

　　We use NTNUI FRO RCOS 16” telescope to observe M5, which focal ratio is F8.4, collocate with ST-10XME CCD camera to take pictures on May 10. We use B and V band filters to take pictures, exposure time is 180sec for each. Between two V band images, we insert one B band image, so that between two same band images, there was about 7 minutes gap,

　　We stop taking images for several minutes when the object is at transit time. After this time, the observe quality is notably better then before. The reason might be the cloud has become less then.

Data Reduction



Results and Discussion