arXiv subjects

Ténéman Keita

Publications and source records attributed to Ténéman Keita.

3 recordsLinked to original sources

arXiv2026

Intergalactic Magnetic Field constraints from detected very high-energy Gamma-Ray Bursts using the Cherenkov Telescope Array Observatory

Defined as the magnetic field permeating cosmic voids, the Intergalactic Magnetic Field (IGMF) is thought to be a relic of the Big Bang, tracing a primordial magnetic seed at the origin of all astrophysical fields. Yet, it has thus far escaped detection. Lower limits on the IGMF strength can be established by observing very high-energy (VHE) photons from extragalactic sources. Specifically, this can be achieved by characterising the time-delayed secondary emission induced by highly energetic transient sources, such as gamma-ray bursts (GRBs). Most studies exclude values of the IGMF below $10^{-17}\;\mathrm{G}$ by comparing the expected effect to the sensitivity curves of various instruments in the $\mathrm{GeV}$ range or above. In this work, we simulate CTAO observation data under realistic observation conditions and perform spectral-temporal fits to estimate the constraints CTAO will bring on the IGMF once fully deployed. We apply the methodology to simulated sources with properties comparable to the few GRBs detected at VHE. In particular, we show that CTAO will probe strengths up to $\sim 10^{-15}\;\mathrm{G}$ when detecting sources similar to GRBs 221009A and 190114C. We also show that existing observations of GRB 221009A by the first CTAO Large Sized Telescope LST-1 favour a strength of $3\times 10^{-17}\;\mathrm{G}$.

astro-ph.HE↗

arXiv2026

Impact of Observational and Modelling Assumptions on Intergalactic Magnetic Field Constraints from TeV Gamma-Ray Bursts with the Cherenkov Telescope Array Observatory

The Intergalactic Magnetic Field (IGMF), permeating cosmic voids, is thought to be a relic of primordial magnetic fields generated in the early Universe and that gave rise to all astrophysical magnetic fields. While it has escaped direct detection, lower limits on its intensity can be derived by characterising the time-delayed secondary emission initiated when primary very high-energy (VHE) photons from gamma-ray bursts (GRBs) produce lepton pairs that are deflected by the IGMF before generating a secondary gamma-ray flux. Most current studies exclude IGMF values below $10^{-18}\;\mathrm{G}$, however, they are typically performed under idealised conditions. Focusing on the impact of modelling and observational choices, we simulate CTAO observations of GRBs 190114C and 221009A under varying conditions. For GRB 190114C-like sources, we establish a stable lower limit of $2\times10^{-16}\;\mathrm{G}$, robust against most variations in source properties and detection strategies. For more extreme GRB 221009A-like events, we demonstrate that CTAO could probe fields up to at least $10^{-16}\;\mathrm{G}$ under harsh conditions, improving significantly the current IGMF constraints.

astro-ph.HE↗

arXiv2025

Expected Constraints on the Intergalactic Magnetic Field using Gamma-Ray Bursts with the Cherenkov Telescope Array Observatory

The InterGalactic Magnetic Field (IGMF), which could permeate the cosmic voids but was never detected so far, is considered a relic of the early Universe. Constraints on its strength $B$ can be derived from its influence on time-delayed very-high-energy photons from Gamma-Ray Bursts (GRBs) in the electromagnetic cascades along their path to the Earth. The present lower limit achieved on its intensity is $10^{-18}\;\mathrm{G}$. In this work, we simulate data from the Cherenkov Telescope Array Observatory (CTAO), accounting for realistic observational constraints, and we apply a joint spectral and temporal fit to characterise the IGMF. GRBs 190114C and 221009A are used as test cases to assess the sensitivity of CTAO. They demonstrate that a broad range of IGMF strengths can be probed with a lower bound as high as $10^{-15}\;\mathrm{G}$. Notably, we show that observations by the CTAO first large telescope, LST-1, already allow us to exclude field strengths up to $3\times 10^{-17}\;\mathrm{G}$.

astro-ph.HE↗