Applying Transit Lightcurve Techniques to Direct Imaging Planet Detection
We developed a new method of extracting astrophysical signals from angular differential imaging (ADI) data, that is closely related to methods applied in transit spectroscopy. Analogous to a planet transiting in front of a star causing a characteristic dip in the light curve, in ADI the planet signal moves over stationary pixels causing a characteristic time-dependent rise in the time series of the pixels that can be modeled. A data-driven model of the temporal behavior of the systematics can be created using reference pixels (Schölkopf et al. 2016, Wang et al. 2016) under the condition that there is a causal connection within the data set, i.e. an underlying cause affecting the systematics of the detector pixels measuring the signal of the planet and all other pixels. We can therefore simultaneously fit the model of the "transit" signal over the detector and reference light curves describing the temporal behavior of the speckle pattern during the transit to find the best fitting model describing the signal.