Sources¶

The morphologies of GW signals can be divided roughly into three categories :cite:`sathyaschutz`, which correspond approximately to the classifications of the astrophysical sources which produce them.

Continuous

signals are expected to be produced by sources over long periods of time. The primary source of continuous sources for ligo are expected to be GW pulsars, but in detectors which are sensitive at lower frequencies, such as the proposed gls:lisa mission, the radiation from inspiralling binary systems should also be detectable.

Stochastic

signals are expected to constitute a background of abpl:gw, produced by the black holes at the centres of galaxies :cite:`1980Natur.287..307B,2001astro.ph..8028P,2003ApJ...583..616J,2008MNRAS.390..192S`, and from the Universe’s inflationary period :cite:`1988PhRvD..37.2078A`.

Transient

Transient signals are strong bursts of GW over a period of seconds or less. The sources of transient signals are normally further sub-divided.

Unmodelled sources, where there are insufficient theoretical models to use matched filtering techniques to search for signals in detector data.

Modelled sources, which currently encompass abbr:cbc sources are sufficiently well understood, in contrast, to allow the use of matched filter searches. These are sources which are primarily expected in the advanced LIGO passband, with compact binary coalescences and supernovae being major targets for burst searches in the advanced observing runs, however there are prospects for burst sources in the gls:lisa regime, for example from hyperbolic encounters between compact objects and stars or other compact objects cite:2012PhRvD..86l4012B,2012PhRvD..86d4017D,2008MPLA…23…99C,2008APh….30..105C,2010MmSAI..81…87D,2005PhRvD..72h4009G,2010PhRvD..82j7501B,2011ApJ…729L..23G.