Colloquium on 7 August 2014
New insights from inside-out Doppler tomography


Title: New insights from inside-out Doppler tomography
Speaker: Enrico Kotze
Date: Thursday, 7 August 2014
Time: 11:20 - 11:40
Venue: SAAO Auditorium


Doppler tomography is a technique that revolutionised the interpretation of orbitally phase-resolved spectroscopic observations of interacting binary stars. We present results of our investigation of using an inside-out Doppler coordinate framework with the intention of reversing the inside-out appearance of binary systems in the standard Doppler framework. The inside-out tomogram is constructed independently from the standard tomogram by directly projecting velocity resolved spectral line profiles onto an inside-out velocity coordinate frame. Effectively, compared to the standard framework, the zero velocity origin is transposed to the the outer circumference and the maximum velocities to the central origin.

In a comparison between standard and inside-out Doppler tomograms of various cataclysmic variables, we show that the inside-out velocity space has the potential to produce new insights into the accretion dynamics in these systems. We show that there is a redistribution of the relative brightness of emission components throughout the tomograms, i.e., where the standard framework tends to concentrate and enhance lower-velocity features towards the smaller area around the origin, the inside-out velocity framework tends to concentrate and enhance higher-velocity features towards the origin. Conversely, the standard framework disperses and smears the higher velocities further away from the origin whereas the inside-out framework disperses and smears the lower velocities. We conclude that inside-out Doppler tomography complements the already powerful tomographic techniques in the analysis of spectroscopic emissions from interacting binary stars.

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