Thick dipolar shock structures onto low mass AM-Her objects

Abstract EN

Thermal instabilities cause the post shock region oscillation on time scales governed by the shock cooling time.

The lowest frequency mode is referred to as the fundamental (F), and the higher frequency modes as the first overtone (10), and second overtone (20) modes respectively.

The F, 10, and 20 modes have been investigated.

For high accretion rates, shocks have heights that are small compared to radius of the star, and only their 10 mode is excited for stellar masses Mt < 0.4 Ms ; where Ms is solar mass.

Mildly low accretion rate shocks are compressively heated before they can cool significantly.

As such, they have shock heights comparable to the radius of the star.

The calculations show undamped first and second overtone modes of oscillation.

Mildly Low accretion rate shock instabilities might be responsible for some of the quasi-periodic oscillations observed on time scales of the order of tens of seconds.