7-9 December 2016
Cochem (Mosel), Germany
Europe/Berlin timezone
Registration Nov 14th | Early bird payment Nov 30th

Multi-frequency blazar variability from decades to minutes

8 Dec 2016, 10:10
20m
Pater Martin Hall (Kapuzinerkloster)

Pater Martin Hall

Kapuzinerkloster

Oral HAP Workshop Variability Methods

Speaker

Dr. Arti Goyal (Astronomical observatory of the Jagiellonian University)

Description

The typical shape of blazar lightcurves' power spectra is a power-law, $P(f) = A f^{-\beta}$, where A is the normalization and $\beta$ is the slope, indicating that the variability is generated by the underlying $\it stochastic$ processes which is of colored noise type (i.e., $\beta \simeq 1-3$). Here we present the results of power spectral analysis of 5 blazars utilizing the $\it Fermi$-LAT survey at high energy $\gamma-$rays, $\it Swift$-XRT and $\it RXTE$-PCA data at X-rays, several ground based observatories and Kepler data at optical and single-dish radio telescopes operating at GHz frequencies (UMRAO and OVRO programmes). The novelty of our approach is that at optical regime, by combining long-term (historical optical light curves) and densely sampled intra-night lightcurves, the PSD characterisitics are investigated for temporal frequencies ranging over 7 orders of magnitude. Our analysis reveals that : (1) nature of processes generating flux variability at optical/radio frequencies is different from those at GeV freqeuncies ($\beta \sim $ 2 and 1, respectively); this could imply, that $\gamma-$ray variability, unlike the Synchrotron (radio-to-optical) one, is generated by superposition of two stochastic processes with different relaxation timescales, (2) the main driver behind the optical variability is same on years, months, days, and hours timescales ($\beta \sim 2$), which argues against the scenario where different drivers behind the long-term flux changes and intra-night flux changes are considered, such as internal shocks due to the jet bulk velocity fluctuation (long-term flux changes) versus small-scale magnetic reconnection events taking place at the jet base (intra-night flux changes). Implications of these results are discussed in the context of blazar emission models.

Primary author

Dr. Arti Goyal (Astronomical observatory of the Jagiellonian University)

Presentation Materials

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