* Astronomy

Title: New Evidence of Magnetic Interactions between Stars from 3D Doppler Tomography of Algol Binaries: Beta Per and RS Vul
Authors: Mercedes T. Richards, Michail I. Agafonov, Olga I. Sharova

Time-resolved H-alpha spectra of magnetically-active interacting binaries have been used to create 3D Doppler tomograms by means of the Radioastronomical Approach. This is the first 3D reconstruction of Beta Per, with RS Vul for comparison. These 3D tomograms have revealed evidence of the mass transfer process (gas stream, circumprimary emission, localised region, absorption zone), as well as loop prominences and coronal mass ejections (CMEs) in Beta Per and RS Vul that could not be discovered from 2D tomograms alone. The gas stream in both binaries may have been deflected beyond the central plane by the mass loser's magnetic field. The stream was more elongated along the predicted trajectory in RS Vul than in Beta Per, but not as pronounced as in U CrB (stream-state). The loop prominence reached maximum Vz velocities of ± 155 km/s compared to ± 120 km/s in Beta Per, while the CME reached a maximum Vz velocity of +150 km/s in RS Vul and +100 km/s in Beta Per. The 3D tomograms show that the gas flows are not symmetric relative to the central plane and are not confined to that plane; a result confirmed by recent 15GHz VLBI radio images of Beta Per. Both the 3D H-alpha tomography and the VLBI radio images support an earlier prediction of the superhump phenomenon in Beta Per: that the gas between the stars is threaded with a magnetic field even though the hot B8V mass gaining star is not known to have a magnetic field.

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