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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. The team:. The plan:. Science Observational Program Preliminary Results. Science.

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two years of blazar monitoring with the ovro 40m telescope at 15ghz in support of the fermi gst

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

the plan
The plan:
  • Science
  • Observational Program
  • Preliminary Results
science
Science

Jets: how are they launched, accelerated, collimated, confined?

Blazars (~aligned AGN)

What is the jet composition?

beamed & boosted

How are particles accelerated to relativistic energies?

fast variability

superluminal motions

high apparent luminosity

What are the details of the emission mechanism, and where in the jet is the observed emission coming from?

high-energy emission

science theory

Blandford & Levinson 1995

Marscher et al. 2008

Dermer, Schlickeiser & Mastichiadis 1991

Lind et al. 1989

Sikora, Begelman & Rees 1994

McKinney 2006

Blandford & Znajek 1977

Blandford & Payne 1982

Science: theory
science phenomenology
Science: phenomenology

What is the correlation between variability, luminosity, beaming?

Blazars (~aligned AGN)

How is emission at different wavelengths correlated?

beamed & boosted

fast variability

Timelags between flares at different frequencies?

superluminal motions

high apparent luminosity

Dependence of variability on spectral properties?

high-energy emission

Cosmic evolution of blazar properties?

phenomenology strategy
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
the ovro 40m program sample and strategy
The OVRO 40m program: sample and strategy
  • Sample: all CGRaBS sources at >200

(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

slide10

The OVRO 40m program: data policy

  • Data: available to Fermi collaboration
  • released to public at ~ time of Fermi public data release
  • regularly updated thereafter

http://www.astro.caltech.edu/GLAST/

ovro 40m program first results
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)
results variability amplitude
Results: Variability Amplitude
  • One blazar: quantify using intrinsic modulation indexflux rms in units of meanm=/<S>
  • Obtain through likelihood analysisaccounting for:
    • uncertainties in individual observations
    • number of observations
slide18

Preliminary

bimodality!

results variability amplitude1
Results: Variability Amplitude

Preliminary

  • Population Studies
slide20

Results: Variability Amplitude

Preliminary

  • Population studies
    • Is the distribution of modulation indices the same at high and low redshifts?

Low z (<1.1)

High z (>1.1)

results correlation with gamma ray emission
Results: Correlation with gamma-ray emission

Preliminary

  • Need longer lightcurves!

Fermi LAT data

OVRO data

summary
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!
variability amplitude population studies
Variability Amplitude - population studies

High z / Low z

(FSRQs only)

2 random equally-sized subsamples

Preliminary

FSRQs vs BLLs