CANGAROO-III Observations of the 2006 Outburst of PKS2155-304

TL;DR

This paper reports CANGAROO-III telescope observations of PKS 2155-304 during a 2006 outburst, detecting significant TeV gamma-ray emission and variability on short timescales, contributing to understanding high-energy blazar activity.

Contribution

First detection of rapid TeV gamma-ray variability from PKS 2155-304 during its 2006 outburst using CANGAROO-III telescopes.

Findings

Detected a 4.8 sigma gamma-ray signal during outburst

Observed flux variability on timescales of hours

Measured flux was about 45% of Crab nebula flux

Abstract

We have used the CANGAROO-III imaging atmospheric Cherenkov telescopes to observe the high-frequency-peaked BL Lacertae (HBL) object PKS 2155-304 between 2006 July 28 (MJD 53944) and August 2, triggered by the H.E.S.S. report that the source was in a high state of TeV gamma-ray emission. A signal was detected at the 4.8 sigma level in an effective live time of 25.1 hours during the outburst period. The flux of Very High Energy gammarays from the CANGAROO-III observations shows the variability on the time scale of less than a few hours. The averaged integral flux above 660 GeV is (1.6 +/- 0.3_stat +/- 0.5_syst) x 10^-11 cm^-2 sec^-1 which corresponds to ~45% of the flux observed from the Crab nebula. Follow-up observations between August 17 (MJD 53964) and 25 indicate the source activity had decreased.