2009 Fermi Symposium, Washington, D.C., Nov. 2-5 1 arXiv:1001.0806v1 [astro-ph.HE] 6 Jan 2010 Submillimeter Variability and the Gamma-ray Connection in Fermi Blazars A. Strom Univ. of Arizona, AZ 85721, USA A. Siemiginowska, M. Gurwell, B. Kelly CfA, MA 02138, USA We present multi-epoch observations from the Submillimeter Array ( SMA ) for a sample of 171 bright 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 de- termined 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 first-order continuous autoregressive processes, from which we derive characteristic timescales. Our blazar sample exhibits no differ- ences in submillimeter variability amplitude or characteristic timescale as a function of subclass or luminosity. 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 blazar class during flaring epochs. The timescales on which high-amplitude flaring events occur in blazars indicate that much of the en- ergy is being produced deep within the jet on small, sub-parsec scales [1, 2]. Understanding if/how emis- sion differs between blazar subclasses (i.e., BL Lacs objects and flat-spectrum radio quasars (FSRQs)) may offer important insight into the similarity be- tween blazars and, furthermore, can provide con- straints on the formation and acceleration of the jets themselves. For the synchrotron component of blazar spectra, the low-frequency spectral break due to synchrotron self-absorption moves to higher frequencies as one measures closer to the base of the jet [2]. This of- ten places the peak of the spectrum in the millime- ter and submillimeter bands, where the emission is optically-thin and originates on parsec and sub-parsec scales [3], allowing direct observation of the most com- pact regions near the central engine. The high en- ergy γ -ray emission originates as a Compton process, typically a combination of synchrotron-self-Compton (SSC) and external-radiation-Compton (ERC). De- pending on the source properties, the synchrotron photons or external photons are upscattered by the same population of electrons that emit the millimeter and submillimeter spectra. Therefore the submillime- ter and γ -ray emission are closely linked and give the full information about the source emission. A systematic study of the submillimeter properties of the entire sample of Fermi blazars has yet to be con- ducted and is one of the primary goals of our work. We present here preliminary analysis of the submillimeter properties of Fermi blazars detected by the Submil- To select our sample, we identified objects in the calibrator list that were also classified as BL Lacs or FSRQs by the Candidate Gamma-Ray Blazar Sur- vey [6, CGRaBS]. Of the 243 total objects in the calibrator list, 171 (35 BL Lacs and 136 FSRQs) have positive blazar class identifications, although there are three sources (J0238+166, J0428-379, and The Submillimeter Array [4] consists of eight 6 m antennas located near the summit of Mauna Kea. The SMA is used in a variety of baseline configurations and typically operates in the 1mm and 850 µ m win- dows, achieving spatial resolution as fine as 0.25” at 850 µ m. The sources used as phase calibrators for the array are compiled in a database known as the SMA Calibrator List 2 [5]. Essentially a collection of bright objects (stronger than 750 mJy at 230 GHz and 1 Jy at 345 GHz), these sources are monitored regularly, both during science observations and dedicated ob- serving tracks. limeter Array 1 ( SMA ) at 1mm and 850 µ m, including an investigation of variable behavior and the deter- mination of submillimeter energy spectral indices. In addition, we consider the connection to the observed γ -ray indices and luminosities. 1. INTRODUCTION 2. SMA BLAZARS $^{1}$The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. $^{2}$http://sma1.sma.hawaii.edu/callist/callist.html eConf C091122