History of UHECR production in Centaurus A

TL;DR

This paper investigates whether past activity episodes of Centaurus A can explain the observed excess of ultra-high-energy cosmic rays from its direction, linking recent activity to cosmic ray production.

Contribution

It links historical activity episodes of Centaurus A to the observed UHECR excess, suggesting recent activity within the last 30 million years as a potential source.

Findings

Recent activity in Cen A is necessary to explain UHECR excess.

The activity period aligns with energization of transition regions and Giant Lobes.

Analysis of energy and composition supports the link between Cen A activity and UHECRs.

Abstract

The origin of the UHECR continues to puzzle, however, an excess of detection in the direction of the radio galaxy Centaurus A (Cen A) raises the possibility of this object being the first UHECR source identifiable. Cen A is known to be currently active, and also exhibits known past episodes of high activity. In this work, we investigate whether the known activity episodes in Cen A may be related to the excess events in the \textit{Centaurus region}. Analysing the energy of the events and the overall mass composition of UHECR, we report that an activity in the last $\sim30$ Myr is necessary to explain the excess of events. This period perfectly fits with the timescale where the transition regions and the Giant Lobes must be energized, as revealed by radio and $\gamma$ ray observations.