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

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 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 is found to be composed of two components of similar strength, one having K $ 100 km s À1 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 $AE250 km s À1 on either side of the central strong H 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.

Dynamical masses of a nova-like variable on the edge of the period gap

“…In this respect, entanglement of the magnetic fields of both stars has been proposed to explain the line emission patterns observed in polars during low states (e.g. Kafka et al 2008;Mason et al 2008).…”

GALEXAND OPTICAL LIGHT CURVES OF WX LMi, SDSSJ103100.5+202832.2, AND SDSSJ121209.31+013627.7

“…During high states of accretion, the stream flow is usually visible as a narrow component in the Balmer emission lines which is mapped to the stream. In normal polars during their low states, high-velocity components in the lines have been interpreted as structures similar to prominences close to the secondary star (Kafka et al 2007(Kafka et al , 2008. However, the Balmer emission in LARPS is weak to non-existent due to the low accretion rates so it would be difficult to construct the map.…”

Orbital periods of cataclysmic variables identified by the SDSS

“…The existence of such a phenomenon was suggested from the observations of stationary central components in the spectra of IP Peg and SS Cyg in outburst (Steeghs et al 1996). Some evidence for these prominences has also been presented for the long-period CV BV Cen (Watson et al 2007) and the magnetic system AM Her (Gänsicke et al 1998;Kafka et al 2008).…”