The Unique Frequency Spectrum of the Blazhko RRc Star LS Her

TL;DR

This study provides detailed photometric analysis of the RRc star LS Her, revealing a unique frequency spectrum and variable Blazhko effect, offering new insights into the complex behavior of RR Lyrae stars.

Contribution

It presents the first detailed frequency analysis of LS Her, showing a unique spectral pattern and cyclic variation of the Blazhko effect, challenging existing theories.

Findings

LS Her has a Blazhko period of approximately 12.75 days.

An unusual equidistant frequency group was observed around the main pulsation frequency.

The Blazhko effect varies cyclically with a period of about 109 days.

Abstract

The Blazhko effect in RR Lyrae stars is still poorly understood theoretically. Stars with multiple Blazhko periods or in which the Blazhko effect itself varies are particularly challenging. This study investigates the Blazhko effect in the RRc star LS Her. Detailed VRI CCD photometry has been performed on 63 nights during six months. LS Her is confirmed to have a Blazhko period of 12.75+/-0.02 days. However, where normally the side frequencies of the Blazhko triplet are expected, an equidistant group of three frequencies is found on both sides of the main pulsation frequency. As a consequence the period and amplitude of the Blazhko effect itself vary in a cycle of 109+/-4 days. LS Her is a unique object turning out to be very important in the verification of the theories for the Blazhko effect.