RR Lyrae variable

The prototype star RR Lyrae was discovered prior to 1899 by Williamina Fleming, and reported by Pickering in 1900 as "indistinguishable from cluster-type variables".

[1]) Using the Canada-France-Hawaii Telescope in the 1980s, Pritchet & van den Bergh found RR Lyraes in Andromeda's galactic halo[2] and, more recently, in its globular clusters.

Some RRab stars, including RR Lyrae itself, exhibit the Blazhko effect in which there is a conspicuous phase and amplitude modulation.

The effect of blending can impact RR Lyrae variables sampled near the cores of globular clusters, which are so dense that in low-resolution observations multiple (unresolved) stars may appear as a single target.

[14] The Kepler space telescope provided accurate photometric coverage of a single field at regular intervals over an extended period.

In Sesar et al. (2017), these stars were used to develop a novel template-fitting technique, achieving highly accurate period estimates with precision better than 2 seconds in over 80% of cases.

[18] Feng et al. (2024) used the Next Generation Virgo Cluster Survey to identify 180 faint RR Lyrae candidates (~21 mag) at galactocentric distances of ~20–300 kpc, with ~100 not previously cataloged in PanSTARRS1 (PS1).

The study applied empirical pulsation fitting techniques, originally developed for the Sloan Digital Sky Survey (SDSS), to analyze these candidates.

Keck II's ESI spectrograph was also used to analyze spectra of distant Milky Way halo RR Lyrae candidates to identify background quasar contaminants in previously mentioned surveys.