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

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.

12 pages, accepted to AJ

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• Probing the Outer Galactic halo with RR Lyrae from the Catalina Surveys
• The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
• The Galactic Thick Disc density profile traced with RR Lyrae stars
• A Search for RR Lyrae Stars in Segue 2 and Segue 3
• Variable stars in the Globular Cluster NGC 2808
• The QUEST RR Lyrae Survey: III. The Low Galactic Latitude Catalogue
• The RR Lyrae Delay-Time Distribution: A Novel Perspective on Models of Old Stellar Populations
• The Identification of RR Lyrae and Delta Scuti Stars from Variable GALEX Ultraviolet Sources
• Microlensing of radially pulsating stars
• A review of pulsating stars from the ASAS data
• An Information Theory Approach on Deciding Spectroscopic Follow Ups
• The BHB stars in the Survey Fields of Rodgers et al. (1993): New Observations and Comparisons with other Recent Surveys
• First direct detection of an RR Lyrae star conclusively associated with an intermediate-age cluster