The Swift UVOT Stars Survey: I. Methods and Test Clusters

TL;DR

This paper introduces a UV survey of nearby stellar populations using Swift's UVOT, demonstrating its effectiveness in studying hot stars and stellar evolution features through color-magnitude diagrams of various clusters.

Contribution

It presents the methods and initial results of a large UVOT survey, showcasing its capability to analyze diverse stellar populations and resolve specific stellar features.

Findings

UVOT can distinguish different stellar populations in clusters.

Color-magnitude diagrams match previous studies.

UVOT identifies specific stellar evolutionary stages.

Abstract

We describe the motivations and background of a large survey of nearby stel- lar populations using the Ultraviolet Optical Telescope (UVOT) aboard the Swift Gamma-Ray Burst Mission. UVOT, with its wide field, NUV sensitivity, and 2.3 spatial resolution, is uniquely suited to studying nearby stellar populations and providing insight into the NUV properties of hot stars and the contribution of those stars to the integrated light of more distant stellar populations. We review the state of UV stellar photometry, outline the survey, and address problems spe- cific to wide- and crowded-field UVOT photometry. We present color-magnitude diagrams of the nearby open clusters M 67, NGC 188, and NGC 2539, and the globular cluster M 79. We demonstrate that UVOT can easily discern the young- and intermediate-age main sequences, blue stragglers, and hot white dwarfs, pro- ducing results consistent with previous studies. We also find that it characterizes the blue horizontal branch of M 79 and easily identifies a known post-asymptotic giant branch star.