Low-Amplitude Variables: Distinguishing RR Lyrae stars from Eclipsing Binaries

TL;DR

This study uses photometry and spectroscopy to accurately classify low-amplitude variable stars, distinguishing RR Lyrae stars from eclipsing binaries, and clarifies their population types in a specific sky region.

Contribution

It provides a new classification approach combining photometry and spectroscopy to differentiate RR Lyrae stars from eclipsing binaries in low-amplitude variables.

Findings

Most RR1 classifications are eclipsing binaries.

Supports Oosterhoff Type I population in the studied field.

Spectroscopic data confirms classifications and population types.

Abstract

It is not easy to identify and classify low-amplitude variables, but it is important that the classification is done correctly. We use photometry and spectroscopy to classify low-amplitude variables in a 246 deg^2 part of the Akerlof et al. (2002) field. Akerlof and collaborators found that 38% of the RR Lyrae stars in their 2000 deg^2 test field were RR1 (type c). This suggests that these RR Lyrae stars belong to an Oosterhoff Type II population while their period distribution is primarily Oosterhoff Type I. Our observations support their RR0 (type ab) classifications, however 6 of the 7 stars that they classified as RR1 (type c) are eclipsing binaries. Our classifications are supported by spectroscopic metallicities, line-broadening and Galactic rotation measurements. Our 246 deg^2 field contains 16 RR Lyrae stars that are brighter than m_R = 14.5; only four of these are RR1 (type c). This corresponds to an Oosterhoff Type I population in agreement with the period distribution.