New Complexities in the Low-State line profiles of AM Herculis

TL;DR

This study provides new high-resolution, time-resolved spectra of AM Her in low state, revealing complex line profile components and their likely origins in magnetic activity and gas flows near the secondary star.

Contribution

It offers detailed spectral analysis of low-state line profiles in AM Her, identifying multiple components and their association with magnetic activity and gas dynamics.

Findings

Central H-alpha feature consists of two components with different radial velocity behaviors.

Satellite components are offset by about ±250 km/sec and linked to magnetic loops near the secondary.

Doppler maps show satellite features at velocities matching L4 and L5 points.

Abstract

When accretion temporarily ceases in the polar AM Her, the emission line profiles are known to develop several distinct components, whose origin remains poorly understood. The new low-state spectra reported here have a more favorable combination of spectral resolution (R~4500), time resolution (~3-min exposures), and S/N than earlier work, revealing additional details of the orbital dependence of the line profiles. The central strong feature of H-alpha is found to be composed of two components of similar strength, one having K~100 km/sec and phased with the motion of the secondary star, the other having little or no detectable radial velocity variations. We attribute the central line component to gas near the coupling region, perhaps with a contribution from irradiation of the secondary star. The two satellite components have RV offsets of ~+/-250 km/sec on either side of the central strong H-alpha peak. These satellites most likely arise in large loops of magnetically confined gas near the secondary star due to magnetic activity on the donor star and/or interactions of the magnetic fields of the two stars. Doppler maps show that these two satellite features have concentrations at velocities that match the velocity locations of L4 and L5 in the system.