Identification of RR Lyrae Variables in SDSS from Single-Epoch Photometric and Spectroscopic Observations

TL;DR

This paper presents a novel method for identifying RR Lyrae stars using single-epoch photometric and spectroscopic data from SDSS, achieving high efficiency and enabling distance and structure analysis of stellar streams.

Contribution

The authors introduce a new variability detection technique based on phase disparities in SDSS data and develop a method to estimate RR Lyrae distances with ~14% precision.

Findings

Detection efficiency of ~85% for RR Lyrae stars.

Identification of stellar streams consistent with previous studies.

Distance estimates with ~14% accuracy for RR Lyrae stars.

Abstract

We describe a new RR Lyrae identification technique based on out-of-phase single-epoch photometric and spectroscopic observations contained in SDSS Data Release 6 (DR-6). This technique detects variability by exploiting the large disparity between the g-r color and the strength of the hydrogen Balmer lines when the two observations are made at random phases. Comparison with a large sample of known variables in the SDSS equatorial stripe (Stripe 82) shows that the discovery efficiency for our technique is ~85%. Analysis of stars with multiple spectroscopic observations suggests a similar efficiency throughout the entire DR-6 sample. We also develop a technique to estimate the average g apparent magnitude (over the pulsation cycle) for individual RR Lyrae stars, using the <g-r> for the entire sample and measured colors for each star. The resulting distances are found to have precisions of ~14%. Finally, we explore the properties of our DR-6 sample of N = 1087 variables, and recover portions of the Sagittarius Northern and Southern Stream. Analysis of the distance and velocity for the Southern Stream are consistent with previously published data for blue horizontal-branch stars. In a sample near the North Galactic Polar Cap, we find evidence for the descending leading Northern arm, and a possible detection of the trailing arm.