black holes and weird pixel effects

In group meeting, Huppenkothen argued out the projects we discussed on Monday related to machine classification of black-hole accretion states of GRS 1915. We talked about all three levels of project: Using supervised methods to transfer classifications for a couple of years of data onto all the other years of data, using unsupervised methods to find out how many classes there plausibly are for the state, and building some kind of generative model either for state transitions or for literally the time-domain photon data. We discussed feature selection for the first and second projects.

Also at group meeting, Foreman-Mackey showed a new Earth-like exoplanet he has discovered in the Kepler data! Time to open our new Twitter (tm) account. He also showed that a lot of his false positives relate to un-discovered discontinuities in the Kepler photometry of stars. After lunch, we spent time investigating these and building (hacky, heuristic) code to find them.

Here are the symptoms of these events (which are sometimes called "sudden pixel sensitivity drops"): They are very fast (within one half-hour data point) changes to the brightness of the star. Although the star brightness drops, in detail if you look at the pixel level, some pixels brighten and some get fainter at the same time. These events appear to have signs and amplitudes that are consistent with a sudden change in telescope pointing. However, they are not shared by all stars on the focal plane, or even on the CCD. Insane! It is like just a few stars jump all at once, and nothing else does. I am confused.

Anyway, we now have code to find these and (in our usual style) split the data at their locations.

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