GWsky is a tool designed to assist astronomers in planning the electromagnetic (EM) follow-up of gravitational-wave (GW) events. Developed in the context of multi-messenger astronomy, GWsky provides a flexible and efficient way to visualize GW sky-localization regions and to generate telescope observation plans that maximize scientific return from limited observing resources. It plays a crucial role in the rapid response to GW triggers, helping ground- and space-based observatories prioritize and schedule observations of the sky regions most likely to contain the astrophysical source.
Core Functionalities
The core functionalities of GWsky include:
- Visualization of GW sky-localization maps using Multi-Order Coverage (MOC) format, which allows for efficient encoding and fast manipulation of irregular probability regions.
- Calculation of visibility windows for given telescope locations, based on constraints such as observatory latitude, local time, airmass limits, moon distance, and twilight.
- Footprint definition and tiling optimization, which helps divide the localization region into telescope-specific fields of view, ordered by probability density.
- Time-domain scheduling, allowing users to produce ranked target lists over time, adjusted for source evolution, visibility gaps, and priority science targets.
GWsky has been used by follow-up teams during real observing runs to coordinate observations between multiple telescopes. GWsky supports both graphical and programmatic interfaces. It can be run as a standalone tool or integrated into automated pipelines triggered by gravitational-wave alerts. It also enables querying of external catalogs (e.g., galaxy catalogs or transient databases), which can be used to weight the localization regions by the expected EM emission or likelihood of host galaxies. This makes it particularly useful for optical, radio, or X-ray follow-up teams aiming to optimize limited telescope time.
Key Features:
GWsky is based on graphical interfaces written using the Tkinter library in Python, which are connected to the Aladin Desktop software through the SAMP protocol (the Simple Application Messaging Protocol). This technical combination offers easy customization of functionalities by users, allowing them to adapt the tool to their specific scientific needs or workflow requirements.
A corresponding web application with the main functionalities is currently available and under active development.