The 2009 Fermi Symposium

Submillimeter Variability and the Gamma-ray Connection in Fermi Blazars

Allison L. Strom

Abstract:

We present multi-epoch observations from the Submillimeter Array (SMA) of a sample of 171 blazars, 43 of which were detected by Fermi during the first three months of observations. We explore the correlation between their gamma-ray properties and submillimeter observations of their parsec-scale jets, with a special emphasis on spectral index in both bands and the variability of the synchrotron component. Subclass is determined using a combination of Fermi designation and the Candidate Gamma-Ray Blazar Survey (CGRaBS), resulting in 35 BL Lac objects and 136 flat-spectrum radio quasars (FSRQs) in our total sample. We calculate submillimeter energy spectral indices using contemporaneous observations in the 1 mm and 850 micron bands during the months August- October 2008. The submillimeter light curves are modeled as continuous first-order autoregressive processes using a routine from Kelly et al. (2009, ApJS, 180, 330), from which we derive characteristic timescales. Our blazar sample exhibits no differences in submillimeter variability amplitude or characteristic timescale as a function of subclass or luminosity. The submillimeter and gamma-ray energy spectral indices place constraints on the peak frequencies of the two spectral components and the population of scatterers but do not necessarily support the spectral sequence interpretation of blazar SEDs (Fossa. et al. 1998, MNRAS, 299, 433). All of the the light curves are consistent with being produced by a single process that accounts for both low and high states, and there is additional evidence that objects may be transitioning between BL Lac- and FSRQ-like states during flaring epochs.