1. Two years of blazar monitoring with the OVRO 40m telescope at 15GHz in support of the Fermi GST Vasiliki Pavlidou (Caltech) on behalf of the OVRO 40m team

2. The team:

3. The plan: Science Observational Program Preliminary Results

4. Science Blazars (~aligned AGN) beamed & boosted fast variability high apparent luminosity superluminal motions high-energy emission Jets: how are they launched, accelerated, collimated, confined? What is the jet composition? How are particles accelerated to relativistic energies? What are the details of the emission mechanism, and where in the jet is the observed emission coming from?

5. McKinney 2006 Blandford & Znajek 1977 Marscher et al. 2008 Blandford & Payne 1982 Dermer, Schlickeiser & Mastichiadis 1991 Lind et al. 1989 Blandford & Levinson 1995 Sikora, Begelman & Rees 1994 Science: theory

6. Science: phenomenology Blazars (~aligned AGN) beamed & boosted fast variability high apparent luminosity superluminal motions high-energy emission What is the correlation between variability, luminosity, beaming? How is emission at different wavelengths correlated? Timelags between flares at different frequencies? Dependence of variability on spectral properties? Cosmic evolution of blazar properties?

7. Phenomenology: strategy Sensitive dependence of observed properties on  Physical processes: everything goes? (different for different blazars or even for different flares of single blazar?) Most impressive behavior need not be typical behavior Need: Large sample Statistically well-defined sample Regular monitoring multiwavelength GeV: Fermi Radio (15 GHz): OVRO 40m

8. The OVRO 40m program: sample and strategy Sample: all CGRaBS sources at  >20 0 (additional sources monitored, not used in population studies, e.g.:non-CGRaBS LAT AGN within accessible sky VERITAS monitoring…) Strategy: twice-a-week flux observations at 15GHz selected based on radio spectral index, radio flux, and X-ray flux

9. The OVRO 40m program: data filters and calibration

10. Data: available to Fermi collaboration released to public at ~ time of Fermi public data release regularly updated thereafter http://www.astro.caltech.edu/GLAST/ The OVRO 40m program: data policy

12. OVRO 40m program: First Results Richards et al. (2009): description of program, lightcurves, statistics of variability for individual objects Max-Moerbeck et al. (2009): population studies of radio variability (also: Fuhrmann et al. 2009: F-GAMMA program description)

13. Results: Lightcurves

15. Results: Variability Amplitude One blazar: quantify using intrinsic modulation index flux rms in units of mean m=  / Obtain through likelihood analysis accounting for: –uncertainties in individual observations –number of observations

18. bimodality!

19. Results: Variability Amplitude Population Studies

20. Population studies –Is the distribution of modulation indices the same at high and low redshifts? Results: Variability Amplitude High z (>1.1) Low z (<1.1)

21. Results: Time Domain

22. Results: Correlation with gamma-ray emission Need longer lightcurves! Fermi LAT data OVRO data

23. Summary Regular multiwavelength monitoring of large and uniform samples critical for blazar science OVRO 40m telescope is monitoring ~1200 CGRaBS blazars @15 GHz ~twice a week Fermi is continuously monitoring the GeV sky First results tantalizing, coming soon at a preprint server near you The future is bright, tune (and/or join) in!

25. Variability Amplitude - population studies High z / Low z (FSRQs only) FSRQs vs BLLs 2 random equally-sized subsamples