K-Stacker, a new way of detecting and characterizing exoplanets with high contrast imaging instruments

TL;DR

K-Stacker is a novel method that enhances exoplanet detection in high contrast imaging by combining long-term observations and orbital modeling, significantly improving detection limits and providing orbital parameters.

Contribution

It introduces the Keplerian-Stacker technique, which improves detection limits by up to tenfold and enables orbital characterization using existing high contrast imaging data.

Findings

Detection limit improved by up to a factor of 10

Method can be combined with ADI techniques

Provides orbital parameters of detected planets

Abstract

This year, a second generation of coronagraphs dedicated to high-contrast direct imaging of exoplanets is starting operations. Among them, SPHERE, installed at the focus of the UT3 Very Large Telescope, reaches unprecedented contrast ratios up to $10^{-6}$ -$ 10^{-7}$, using eXtreme Adaptive Optics and the Angular Differential Imaging (ADI) techniques. In this paper, we present a new method called Keplerian-Stacker that improves the detection limit of high contrast instruments like SPHERE, by up to a factor of 10. It consists of observing a star on a long enough period to let a hypothetical planet around that star move along its orbit. Even if in each individual observation taken during one night, we do not detect anything, we show that it is possible, using an optimization algorithm, to re-center the images according to keplerian motions (ex: 10-100 images taken over a long period of typically 1-10 years) and detect planets otherwise unreachable. This method can be used in combination with the ADI technics (or possibly any other high contrast data reduction method) to improve the Signal to Noise Ratio in each individual image, and to further improve the global detection limit. It also directly provides orbital parameters of the detected planets, as a by-product of the optimization algorithm.