Fermi Gamma-ray Space Telescope

An Optical 10-Year Blazar Data Archive for Fermi and the Masses

Paul Smith


Since the launch of the Fermi Gamma-ray Space Telescope, Steward Observatory has made public optical observations of gamma-ray-bright blazars obtained with the SPOL spectropolarimeter. During the first decade of the Fermi mission, an archive of nearly 13,000 spectropolarimetric observations and over 10,000 flux measurements has been amassed for several dozen blazars that can often be detected by the Large Area Telescope (LAT) aboard Fermi within a few days or less. The optical program complements the all-sky, nearly continuous high energy measurements of the LAT as well as other large-scale, ground-based programs to observe blazars at TeV energies and in the radio using both single-dish and VLBI facilities. The Steward Observatory data provide polarization, flux, and spectral information of this important sample of blazars, allowing for studies of blazar variability from daily to yearly time scales in relation to the behavior observed at other wavelengths. Emphasis has been placed on accurate spectropolarimetry. As a result, these data provide invaluable information on polarization variability, the magnetic field structure within the beamed emission regions, relationships between the optical and radio polarization as jet structures resolved by VLBI observations evolve, and test possible connections between the synchrotron continuum and the gamma rays that Fermi observes. This research is supported by Fermi Guest Investigator Program grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G.