Data Reduction Techniques for High Contrast Imaging Polarimetry. Applications to ExPo
Abstract
Imaging polarimetry is a powerful tool for detecting and characterizing exoplanets and circumstellar environments. Polarimetry allows a separation of the light coming from an unpolarized source such as a star and the polarized source such as a planet or a protoplanetary disk. Future facilities like SPHERE at the VLT or EPICS at the E-ELT will incorporate imaging polarimetry to detect exoplanets. The Extreme Polarimeter (ExPo) is a dual-beam imaging polarimeter that currently can reach contrast ratios of 10^5, enough to characterize circumstellar environments. We present the data reduction steps for a dual-beam imaging polarimeter that can reach contrast ratios of 10^5. The data obtained with ExPo at the William Herschel Telescope (WHT) are analyzed. Instrumental artifacts and noise sources are discussed for an unpolarized star and for a protoplanetary disk (AB Aurigae). The combination of fast modulation and dual-beam techniques allow us to minimize instrumental artifacts. A proper data processing and alignment of the images is fundamental when dealing with large contrasts. Imaging polarimetry proves to be a powerful method to resolve circumstellar environments even without a coronagraph mask or an Adaptive Optics system.
Cite
@article{arxiv.1105.2961,
title = {Data Reduction Techniques for High Contrast Imaging Polarimetry. Applications to ExPo},
author = {H. Canovas and M. Rodenhuis and S. V. Jeffers and M. Min and C. U. Keller},
journal= {arXiv preprint arXiv:1105.2961},
year = {2015}
}
Comments
9 pages, 12 Figures, Accepted for publication in A&A