Discovery of a Magnetic White Dwarf in the Symbiotic Binary Z Andromedae
نویسنده
چکیده
We report the first result from our survey of rapid variability in symbiotic binaries: the discovery of a persistent oscillation at P = 1682.6±0.6 s in the optical emission from the prototype symbiotic, Z Andromedae. The oscillation was detected on all 8 occasions on which the source was observed over a timespan of nearly a year, making it the first such persistent periodic pulse found in a symbiotic binary. The amplitude was typically 2 − 5 mmag, and it was correlated with the optical brightness during a relatively small outburst of the system. The most natural explanation is that the oscillation arises from the rotation of an accreting magnetic (BS ∼> 10 G) white dwarf. This discovery constrains the outburst mechanisms, since the oscillation emission region near the surface of the white dwarf was visible during the outburst. Subject headings: accretion — binaries: symbiotic — stars: magnetic fields — stars: oscillations — stars: rotation — white dwarfs
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