Spectropolarimetry of Dwarf Novae in Outburst: First Results of a Survey

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Session 21 -- Cataclysmic Variables, Dwarf Novae
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[21.15] Spectropolarimetry of Dwarf Novae in Outburst: First Results of a Survey

J.J.Johnson, N.E.B.Zellner, L.Griscom, J.Hanson, P.Mader, S.Pozdell, B.Ager, R.Banetzke, B.Chandra, G.Niesl (UW-Madison, Space Astronomy Laboratory)

We have recently begun a campaign of observing dwarf novae in outburst using the spectropolarimeter at the University of Wisconsin's Pine Bluff Observatory (PBO). Theoretically, the optical light from dwarf novae should show some intrinsic polarization. Cheng et al. (1988, Ap.J. 328, 223) have presented calculations demonstrating that electron scattering can cause linear polarization of the thermal radiation from the accretion disks of dwarf novae in eruption. Another source of polarized light could be electron scattering in the gas ejected during the dwarf nova eruption if this mass were ejected aspherically. The first polarigenic mechanism will result in a polarized continuum with depolarization through the emission lines. In the second case, however, the emission lines should be polarized but the continuum should be unpolarized, as has been observed in some WR stars and SN 1987a. Both mechanisms may occur in the same object, however. We present spectropolarimetric observations of SS Cyg and other dwarf novae in outburst. The observations of SS Cyg show little evidence of polarization changes through its optical spectrum. Its continuum polarization, however, is higher than predicted by the calculations of Cheng et al. (1988).

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