Detector Characterization in LIGO's Fourth Observing Run

The Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors are currently taking data for LIGO's fourth observing run (O4). The detectors are operating better than ever before in O4, with around a hundred significant detection candidates of coalescing compact binaries released so far. Meanwhile, searches probe LIGO data in the hopes of uncovering novel signal types: bursts of gravitational waves from supernova core collapses, continuous waves from spinning neutron stars, evidence of the stochastic gravitational wave background, and more.

At the junction between detector science and astrophysical searches lies detector characterization. The LIGO detector characterizaton group enables current and future LIGO science by working to understand detector noise and to mitigate its impacts on searches. In this talk I will provide an overview of LIGO detector characterization in O4, with a focus on how the wide variety of gravitational-wave search types motivate an equally wide variety of noise investigations.