Speaker
Apply to be<br> considered for a student <br> award (Yes / No)?
Yes
Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)?
Yes
Main supervisor (name and email)<br>and his / her institution
Russ Taylor, russ@ast.uct.ac.za, University of Cape Town
Abstract content <br> (Max 300 words)<br><a href="http://events.saip.org.za/getFile.py/access?resId=0&materialId=0&confId=34" target="_blank">Formatting &<br>Special chars</a>
We report the possible detection of a quasi-periodic oscillation (QPO) in the polarized flux of the gamma-ray emitting blazar PKS 2155-304. The source was recorded with the HIgh-Speed Photo-POlarimeter (HIPPO), which was mounted on the 1.9 m Radcliffe telescope, operated by the South African Astronomical Observatory (SAAO). The microvariability of the polarization was observed from 25 to 27 July 2009 using a temporal resolution of 5 minutes. During this time, the mean daily polarization degree increased from roughly 3% to 10%. Simultaneous very high-energy (VHE, photons exceeding GeV energies) gamma-ray measurements with the High Energy Stereoscopic System (H.E.S.S.) showed that this increase in the polarization degree coincided with an increase in the gamma-ray flux of the source. Inspection of the intranight variability of the polarization showed that, on 24 July 2009, the polarized flux appeared to be modulated by a periodic component. This polarized QPO occurred at the onset of the increase in gamma-ray activity in PKS 2155-304, which was itself preceded by a gamma-ray flare that reached its peak flux on 23 July 2009, one day before the QPO developed. A periodogram of the polarized flux revealed the presence of a significant peak at a frequency corresponding to period of ~30 minutes. PKS 2155-304 is one of a small number of active galactic nuclei (AGN) for which convincing evidence of QPOs have been found. The most recent claim is a ~4.6 hour periodicity that was detected on 1 May 2006 with the XMM-Newton telescope at X-ray energies (0.3-10 keV). This is the first detection of QPO activity from blazars in the optical and polarized light, opening up a new method of studying the AGN phenomenon.
Level for award<br> (Hons, MSc, <br> PhD, N/A)?
PhD
Please indicate whether<br>this abstract may be<br>published online<br>(Yes / No)
Yes
