photon pile-up

At Blanton–Hogg group meeting, Daniela Huppenkothen brought up photon pile-up in x-ray and gamma-ray detectors. The issue is that if two photons arrive at the same time, or in the same electronics-restricted time window, they will appear as one photon, but of higher energy. It is an issue for Chandra and for Fermi, among other assets. This pile-up leads to a distortion of the spectrum (and point-spread function, and so on) of very bright sources. We discussed how one might model this, given that it is easy to simulate but hard to describe with a likelihood function. We also came up with a ridiculously simple idea for testing cosmic-ray detection in time-series imaging, which really, really needs to e done.

In the afternoon, I did text writing and problem (exercise) writing in my MCMC tutorial. Stay on target. #AcWriYear

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