tilepy: rapid tiling strategies in mid/small FoV observatories

TL;DR

The paper introduces 'tilepy', a Python package that rapidly generates optimized observation schedules for small/mid-FoV telescopes to efficiently follow up poorly localized multi-messenger events, enhancing detection chances.

Contribution

The paper presents novel, flexible tiling algorithms integrated into 'tilepy' for rapid, multi-observatory follow-up of large uncertainty events, extending previous GW-focused strategies.

Findings

Proven success in GW follow-up with H.E.S.S. during O2 and O3.

Effective scheduling for GW170817 BNS merger.

Generalization to GRB alerts from Fermi-GBM.

Abstract

The challenges inherent to time-domain multi-messenger astronomy require strategic actions so that adapted, optimized follow-up observations are performed efficiently. In particular, poorly localized events require dedicated tiling and/or targeted, follow-up campaigns so that the region in which the source really is can be efficiently covered, increasing the chances to detect the multi-wavelength counterpart. We have developed the python package "tilepy" to rapidly derive the observation scheduling of large uncertainty localization events by small/mid-FoV instruments. We will describe several mature follow-up scheduling strategies. These range from an option to use of low-resolution grids, to the full integration of sky regions and targeted observations using galaxy catalogs. The algorithms consider the visibility constraints of customisable observatories and allow to schedule observations in both astronomical darkness and in moonlight conditions. Developed initially to provide a rapid response to gravitational wave (GW) alerts by Imaging Atmospheric Cherenkov Telescopes (IACTs), they have been proven successful, as shown by the GW follow-up during O2 and O3 with the H.E.S.S. telescopes, and particularly in the follow-up of GW170817, the first binary neutron star (BNS) merger ever detected. Here we will present a generalisation of these rapid strategies to other alerts showing large uncertainties in the localization, like Gamma-Ray Burst (GRB) alerts from Fermi-GBM. We will also demonstrate the flexibility of {\it tilepy} in scheduling observations for a large variety of observatories. We will conclude by describing the latest developments of these algorithms that are able to derive optimised follow-up schedules across multiple observatories and networks of telescopes.