An outer-disk SX Phe variable star in Rubin Data Preview 1

TL;DR

This paper reports the discovery of an SX Phoenicis variable star in Rubin Data Preview 1, demonstrating the potential for large-scale variable star detection in upcoming Rubin Observatory data, and associating it with the Monoceros Ring.

Contribution

First identification of an SX Phe star in Rubin Data Preview 1, illustrating the survey's capability to detect numerous variable stars and their potential Galactic structure associations.

Findings

Star is an SX Phe pulsator with a 0.0767-day period.

Distance to star is estimated at 16.6 kpc.

Likely part of the Monoceros Ring structure.

Abstract

We report the discovery of an SX Phoenicis-type pulsating variable star via 217 epochs of time-series photometry from the Vera C. Rubin Observatory's Data Preview 1. The star, designated LSST-DP1-O- 614435753623041404 (or LSST-C25_var1 for short), has mean magnitudes of $(\langle g\rangle, \langle r\rangle) = (18.65, 18.63)$, with pulsation amplitudes of (0.60, 0.38)~mag in these bands. Its period is 0.0767 days (1.841 hours), typical of SX Phe pulsators. We derive a distance to the star of 16.6 kpc based on an SX Phe period-luminosity relation. Its position $\sim5$ kpc from the Galactic plane, in the outer Milky Way disk at a Galactocentric distance of $\sim22$ kpc, and its proper motion suggest that LSST-C25_var1 is part of the Monoceros Ring structure. This star is presented as a small taste of the many thousands of variable stars expected in Rubin/LSST data.