1305.5846 (J. C. A. Miller-Jones et al.)

An accurate geometric distance to the compact binary SS Cygni vindicates accretion disc theory    [PDF]

J. C. A. Miller-Jones, G. R. Sivakoff, C. Knigge, E. G. Körding, M. Templeton, E. O. Waagen

Dwarf novae are white dwarfs accreting matter from a nearby red dwarf companion. Their regular outbursts are explained by a thermal-viscous instability in the accretion disc, described by the disc instability model that has since been successfully extended to other accreting systems. However, the prototypical dwarf nova, SS Cygni, presents a major challenge to our understanding of accretion disc theory. At the distance of 159 +/- 12 pc measured by the Hubble Space Telescope, it is too luminous to be undergoing the observed regular outbursts. Using very long baseline interferometric radio observations, we report an accurate, model-independent distance to SS Cygni that places the source significantly closer at 114 +/- 2 pc. This reconciles the source behavior with our understanding of accretion disc theory in accreting compact objects.

View original: http://arxiv.org/abs/1305.5846