Image Details
GWTC-4.0: An Introduction to Version 4.0 of the Gravitational-Wave Transient Catalog
A. G. Abac et al 2025 The Astrophysical Journal Letters 995 .
Caption: Figure 4.
Relationship between the sky location in equatorial coordinates, the polarization angle, and the GW coordinate frame. The direction from the source to Earth is N, and the vector X defines a reference direction on the transverse plane called the wave plane. The location of the source on the sky in the equatorial coordinate system is given by its R.A. α and decl. δ. The polarization angle ψ is the angle counterclockwise about N between the equatorial plane and X. Also shown is the Greenwich sidereal time (GST), the angle between the first point of Aries ﹩\unicode{9800}﹩ and the prime meridian, and the Greenwich hour angle (GHA) of the source, GHA = GST − α. NCP is the north celestial pole.
© 2025. The Author(s). Published by the American Astronomical Society.