Evidence for a QPO structure in the TeV and X-ray light curve during the 1997 high state Gamma emission of Mkn 501

TL;DR

This study presents evidence of a 23-day quasi-periodic oscillation in the TeV and X-ray light curves of Mkn 501 during its 1997 high activity state, indicating a possible common underlying process.

Contribution

First detection of a consistent 23-day QPO in both TeV and X-ray data of Mkn 501 during a high state, using combined observational analysis.

Findings

Evidence for a 23-day periodicity in TeV light curve

Evidence for the same periodicity in X-ray light curve

Combined probability of the periodicity is 2.8 x 10^-4

Abstract

The BL Lac Object Mkn 501 was in a state of high activity in the TeV range in 1997. During this time Mkn 501 was observed by all Cherenkov-Telescopes of the HEGRA-Collaboration. Part of the data were also taken during moonshine thus providing a nearly continuous coverage for this object in the TeV-range. We have carried out a QPO analysis and found evidence for a 23 day periodicity. We applied the same analysis on the 'data by dwell' x-ray lightcurve from the RXTE/ASM database and found also evidence for the 23 day periodicity. The combined probability was P = 2.8 *10^-4.