Cataclysmic (Explosive and Novalike) Variables

Abstract

There are almost 800 cataclysmic variables (CVs) identified within the General Catalog of Variable Stars. The group with the most members within this class are the dwarf novae (U Geminorum type) that include the subtypes: UGSS, UGSU and UGZ. The dwarf novae (DN) are the longest-known and best-studied cataclysmic variables. They are observed extensively by amateur astronomers because of their recurring fast rise to brightness. To some extent, professionals rely upon amateurs to notify them when one of these stars goes into “outburst,” the sudden brightening for which these variables are known. Professional astronomers are not able to constantly check the large number of dwarf novae for outbursts that can appear at largely, unpredictable times.

These are variable stars showing outbursts caused by thermonuclear burst processes in their surface layers (novae) or deep in their interiors (supernovae). We use the term “novalike” for variables that show novalike outbursts caused by rapid energy in the surrounding space volume (UG type stars) and also for objects not displaying outbursts but resembling explosive variables at minimum light by their spectral (or other) characteristics. The majority of explosive and novalike variables are close binary systems, their components having strong mutual influence on the evolution of each star. It is often observed that the hot dwarf component of the system is surrounded by an accretion disk formed by matter lost by the other, cooler, and more extended component.

GCVS