New Complexities in the Low-State Line Profiles of AM Herculis

• Published in: The Astrophysical journal Vol. 688; no. 2; pp. 1302 - 1314
• Main Authors: Kafka, S, Ribeiro, T, Baptista, R, Honeycutt, R. K, Robertson, J. W
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.12.2008; IOP
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; stars: individual (AM Herculis); Line shape; stars: magnetic fields; Novae; Magnetic stars; Cataclysmic variable stars; Stellar activity; Magnetic fields; stars: activity; Complexity; novae, cataclysmic variables
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/592186

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, time resolution ([image]3 minute 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 [image] km s super(-1) 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 radial velocity offsets of [image]+/-250 km s super(-1) 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.