Probing the Disk-Jet Connection in Fermi Gamma-Ray Bright Blazars
Abstract
Relativistic jets in blazars produce radio through gamma-ray emission, via synchrotron radiation at long wavelengths and inverse Compton scattering at gamma-ray energies. Variability across these wavelengths allows us to estimate the densities and energies of the radiating particles. Yet, the physics of blazar jets is still uncertain; e.g., it is not clear whether the gamma-rays come from sub- or kilo-parsec scales. The unprecedented temporal and spectral sensitivity of the Fermi Space Telescope has ushered in a new era of discovery and over the past 5 years I have obtained queue-scheduled, nightly optical-infrared (OIR) photometry and bi-weekly optical spectroscopy using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m+Andicam and 1.5m+RCSpec, in Cerro Tololo, Chile; totaling ~70 gamma-ray bright blazars that are detected nightly with Fermi. In my dissertation, I analyze 5 years of bi-monthly spectroscopy of 6 blazars. I find that the broad lines - which are presumably photoionized by the accretion disk - vary substantially less than the OIR continuum, which is dominated by the Doppler-beamed jet. However, during the largest gamma-ray flares in 3C 454.3 and PKS 1510-089, I see significant broad emission line variations, with lags on the order days and infer that the jet, in its brightest state, contributes significantly to photoionizing the broad-line clouds, meaning the gamma-emitting region is within the broad line region at sub-parsec scales. These variations are not seen at lower gamma-ray fluxes or in any other blazars we observed. I also describe inferences about the jet physics obtained from the SMARTS OIR photometry, which is well correlated with the gamma-ray flux for 11 blazars, with lags of less than one day, strongly supporting the inverse Compton model for gamma-ray production. In addition, color changes in the OIR constrain the ratio of thermal disk to non-thermal jet emission. The color evolution differs by source and also in a given source over timescales of years. In summary, the results of this dissertation provide strong constraints on the location of the gamma-emitting region and the spectral evolution of flaring blazars on short and long timescales.
- Publication:
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American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22321003I