Replicated Echelle Diagrams in Asteroseismology: A Tool for Studying Mixed Modes and Avoided Crossings

Abstract

In oscillating stars, mixed modes have p-mode character in the envelope and g-mode character in the core. They are observed in subgiants and red giants, in which the large density gradient outside the core effectively divides the star into two coupled cavities. This leads to the phenomenon of mode bumping, in which mode frequencies are shifted from their regular spacing as they undergo avoided crossings. This short contribution introduces a new diagram that involves extending the traditional echelle diagram by replication. This new diagram should prove a useful way of displaying mixed modes and helping to identify missing modes that may lie below the detection threshold.