Contribution
43 GHz light curve of the nucleus of Centaurus A
Presenter: Zulema Abraham (University of São Paulo)
Abstract: The spectral energy distribution of the nucleus of Centaurus A, extending from radio to γ-rays, is similar to that of blazars, although the position of the low energy maximum is not well defined because of the uncertainty in the optical absorption. The recent detection of TeV emission from this object strengthens this supposition, which requires the synchrotron origin of both radio and X-rays. In this work we report the 43 GHz light curve of the core of Centaurus A during the last six years, with timescales of days, and months. The observations were made with the Itapetinga radiotelescope that has a resolution of about 2 arcmin at this frequency. The observing technique consisted of scans with 24 arcmin amplitude, centered at the core and passing through the two inner lobes, which were used for instantaneous calibration. The core of Centaurus A seems to have entered a phase of high activity during the last two years, with fast and high amplitude variability, well correlated with the 2-10 keV patterns observed by the ASM of the RXTE observatory. The delay between the two light curves favor the interpretation of a common synchrotron origin of both emissions, with the delay at radio frequencies due to variation of the optical depth, probably produced in an expanding source.