EUVE and VLA Observations of the Eclipsing Pre-Cataclysmic Variable V471 Tauri

S.L. Cully, J. Dupuis, T. Rodriguez-Bell, G. Basri, O.H.W. Siegmund, J. Lim, S.M. White

Proceedings of IAU Colloquium 152: Astrophysics in the Extreme Ultraviolet, 1996

Abstract

We present observations of the eclipsing binary V471 Tauri by the Extreme Ultraviolet Explorer (EUVE) and the Very Large Array (VLA). The EUV spectrum is dominated by the continuum of the hot white dwarf and the time-averaged spectrum is fitted by a (33.1 +/- 0.5)E3 K pure hydrogen white dwarf atmosphere assuming log g = 8.5. An ISM hydrogen column density of (1.5 +/- 0.4)E18 cm^(-2) is required to explain the attenuation of the white dwarf spectrum thus setting the H I column in the line of sight of the Hyades cluster. The He II lambda 304 A line is in emission and varies over the orbital period of V471 Tauri following a sinusoidal modulation with the maximum reached when the K star is at inferior conjunction. Transient dips are detected at orbital phase -0.12 in the SW and MW spectrometers integrated lightcurves but are notably absent in the LW lightcurve indicating the occulting material is ionized. The VLA observation suggest the presence of a K star coronal magnetic loop between the two stars reconnecting with the white dwarf magnetic field. Such a structure could be the occulting source needed to explain the dips seen in the lightcurves of V471 Tauri in the EUV.

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