Introduction
GLAST/LAT and the IACTs will be unprecedently close in energy coverage, thanks to the increased efficiency at high energies of the LAT compared to EGRET, and the lower thresholds of recent IACTs. This makes the concept of a cross-calibration between the two techniques possible. How, when and by how much can the absolute energy scale/flux scale be improved for IACTS?
- Currently ACT systematic calibration uncertainties (energy and sensitivity) are ~ 30%
- The ACT energy resolution can be as good as 5% but the absolute energy scale isdominated by uncertainties on Monte Carlo simulations and atmospheric models.
- Using LAT observations at high energies to reduce those systematic errors of ground-based observatories has been mentioned elsewhere (refs).
- A good source would be bright, with a known spectrum that could possibly contain a spectral feature.
- Given such a source, it would probably not be visible by all ACTs..
Documentation
LAT/VHE cross calibration
- Using the photons from the Crab Nebula seen by GLAST to calibrate MAGIC and the Imaging Air Cherenkov Telescopes, Bastieri et al, Astropart.Phys. 23 (2005) 572-576
Other space based cross calibrations