Coordinated Fermi/Optical Monitoring of Blazars and the Great 2009 September Gamma-ray Flare of 3C 454.3
msra(2009)
摘要
We describe the optical spectropolarimetric monitoring program at Steward
Observatory centered around gamma-ray-bright blazars and the LAT Monitored
Source List planned for Fermi Cycles 2-4. The large number of measurements made
during Cycle 1 of the Fermi mission are available to the research community and
the data products are summarized (see
http://james.as.arizona.edu/~psmith/Fermi). The optical data include
spectropolarimetry at a resolution of ~20 A, broad-band polarization and flux
measurements, and flux-calibrated spectra spanning 4000-7600 A. These data
provide a comprehensive view of the optical variability of an important sample
of objects during the Fermi Era. In addition to broad-band flux and linear
polarization monitoring, the spectra allow for the tracking of changes to the
spectral index of the synchrotron continuum, importance of non-synchrotron
emission features, and how and when the polarization varies with wavelength, an
important clue as to the structure of the emission region or the identification
of multiple nonthermal components. As an illustration, we present observations
of 3C 454.3 obtained in 2009 September during an exceptionally bright gamma-ray
flare. The blazar was optically bright during the flare, but except for a few
short periods, it showed surprisingly low polarization (P < 5%). Opportunities
exist within the Fermi research community to coordinate with our long-term
optical monitoring program toward the goal of maximum scientific value to both
the Fermi and associated radio VLBI monitoring of blazars.
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关键词
high energy astrophysics,gamma ray,importance sampling
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