Speakers
Description
Sagittarius A (Sgr A), the supermassive black hole at the center of the Milky Way, provides a unique laboratory for investigating high-energy emission processes and the dynamics of matter in strong gravitational fields. Detecting periodic or quasi-periodic variability in its gamma-ray emission can provide important constraints on particle acceleration mechanisms, accretion processes, and relativistic dynamics in the vicinity of the event horizon.
Using publicly available gamma-ray observations from the Fermi Large Area Telescope (Fermi-LAT) and the Fermitools software package, we constructed 867-day light curves of Sagittarius A* covering the period from 2008 to 2024. In total, 1,463,040 minutes of observations were analyzed in a systematic search for periodic and quasi-periodic signals. To assess the temporal behavior of the source, we employed a combination of statistical and computational inference techniques, including Lomb–Scargle periodograms, window-function analysis, noise-colour characterization, phase-folding methods, unsupervised machine learning through K-Means clustering, Markov Chain Monte Carlo (MCMC) inference, and likelihood fitting using Jacobi elliptic functions.
Our analysis reveals a statistically significant quasi-periodic oscillation characterized by an enhanced gamma-ray emission phase lasting approximately 78 minutes, followed by a quiescent interval of about 18 minutes, resulting in a total oscillation timescale of approximately 96 minutes. The signal is consistently recovered by multiple independent methods and remains robust against observational sampling effects and colored-noise contamination.
We discuss possible interpretations of these timescales in terms of orbital motion near the innermost regions of the accretion flow, magnetohydrodynamic instabilities, hot-spot models, and other relativistic processes operating around the Galactic Center black hole. If confirmed through future multiwavelength observations, these oscillations may provide new constraints on the physical conditions and dynamical structure of the plasma surrounding Sagittarius A*.