Further evidence of shocks in the first-overtone RR Lyrae pulsators: first detection of shock-triggered magnesium emissions

TL;DR

This study provides the first spectroscopic evidence of shock-triggered magnesium emissions in a non-fundamental mode RR Lyrae pulsator, revealing shock wave behavior and emission duration longer than previously observed.

Contribution

It reports the first detection of shock-triggered magnesium emissions in a non-Blazhko RRc pulsator, advancing understanding of shock phenomena in these stars.

Findings

Detection of blueshifted Mg triplet emission in RRc pulsator

Confirmation of shock waves through emission evolution

Shock-triggered emission lasts over 15% of pulsation cycle

Abstract

The behavior of the shock wave in the atmosphere of the non-fundamental mode RR Lyrae pulsator remains a mystery. In this work, we firstly report a blueshifted Mg triplet emission in continuous spectroscopic observations for a non-Blazhko RRc pulsator (Catalina-1104058050978) with LAMOST medium resolution spectra. We analyse the photometric observations from Catalina Sky Survey of this RRc pulsator with pre-whitening sequence method and provide the ephemeris and phases. An additional frequency signal with $P_1/P_x = 0.69841$ is detected and discussed. The redshift and radial velocity of the spectra are provided by fitting process with $S\acute{e}rsic$ functions and cross-correlation method. Moreover, we plot the variation of H$\alpha$ and Mg lines in a system comoving with the pulsation. Clear evolution of comoving blueshifted hydrogen and Mg emission is observed, which further confirms the existence of shock waves in RRc pulsators. The shock-triggered emission lasts over $15\%$ of the pulsation cycle, which is much longer than the previous observations.