Cataclysmic Variable Star - Classification

Classification

Cataclysmic variables are subdivided into several smaller groups, often named after a bright prototype star characteristic of the class. In some cases the magnetic field of the white dwarf is strong enough to disrupt the inner accretion disk or even prevent disk formation altogether. Magnetic systems often show strong and variable polarization in their optical light, and are therefore sometimes called polars; these often exhibit small-amplitude brightness fluctuations at what's presumed to be the period of rotation of the white dwarf

(Classical) novae

These cataclysmic variables have very large outbursts, of 6 to 19 magnitudes, caused by thermonuclear fusion of material accreted onto the white dwarf.

Recurrent novae

These have outbursts of about 4 to 9 magnitudes, repeating every 10 to 80 years. Examples include T Pyxidis and RS Ophiuchi.

Dwarf novae

Dwarf novae, or U Geminorum stars, are cataclysmic variables which are observed to brighten repeatedly, though by a smaller amount than classical novae.

Z Camelopardalis stars	Temporarily "halt" at a particular brightness below their peak
SU Ursae Majoris stars	Have "superoutbursts" which are brighter than the average
SS Cygni stars	Have outbursts of two distinct lengths

Polars

AM Herculis	These are stars where the magnetic field of the white dwarf has locked the binary into synchronous rotation, and matter streams down fairly constantly onto the white dwarf rather than forming a disc.
DQ Herculis	Also called 'intermediate polars', these have a slightly weaker magnetic field than AM Herculis stars; there is an accretion disc, but substructure in it is created by the field.

VY Sculptoris

These are stars which occasionally drop in brightness by more than one magnitude, with very occasional dwarf-nova-type outbursts during the dim state. They may be a subclass of polars.

AM Canum Venaticorum

These are cataclysmic variables both of whose components are white dwarfs; the accretion disc is composed primarily of helium, and they are of interest as sources of gravitational waves.

SW Sextantis

These are like dwarf novae but have the accretion disc in a steady state, so don't show outbursts; the disc emits non-uniformly. They are usually also eclipsing variables, though this appears to be a selection artefact.

There are over 1600 known CV systems. The catalog was frozen as of 1 February 2006 though more are discovered each year.

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