Kammerer, JensIreland, Michael J.Martinache, FrantzGirard, Julien H.2025-03-172025-03-17researchoutputwizard:u3102795xPUB4861Scopus:85072296449WOS:WOS:000474894100050https://dspace-test.anu.edu.au/handle/1885/733720527Directly imaging exoplanets is challenging because quasi-static phase aberrations in the pupil plane (speckles) can mimic the signal of a companion at small angular separations. Kernel phase, which is a generalization of closure phase (known from sparse aperture masking), is independent of pupil plane phase noise to second order and allows for a robust calibration of full pupil, extreme adaptive optics observations. We applied kernel phase combined with a principal component based calibration process to a suitable but not optimal, high cadence, pupil stabilized L'-band ($3.8\, {\mu \rm m}$) data set from the ESO archive. We detect eight low-mass companions, five of which were previously unknown, and two have angular separations of ∼0.8-1.2 λ/D (i.e. ∼80-$110\, \text{mas}$), demonstrating that kernel phase achieves a resolution below the classical diffraction limit of a telescope. While we reach a 5σ contrast limit of ∼1/100 at such angular separations, we demonstrate that an optimized observing strategy with more diversity of PSF references (e.g. star-hopping sequences) would have led to a better calibration and even better performance. As such, kernel phase is a promising technique for achieving the best possible resolution with future space-based telescopes (e.g. James Webb Space Telescope), which are limited by the mirror size rather than atmospheric turbulence, and with a dedicated calibration process also for extreme adaptive optics facilities from the ground.MJI was supported by the Australian Research Council Future Fellowship (FT130100235). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement CoG #683029). JHG gratefully acknowledges support from the Director’s Research Funds at the Space Telescope Science Institute. The manuscript was also substantially improved following helpful comments from an anonymous referee.16EnglishPublisher Copyright: © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.binaries: closeplanets and satellites: detectionplanets and satellites: formationtechniques: high angular resolutiontechniques: image processingtechniques: interferometric2019-06-1110.1093/mnras/stz882http://www.scopus.com/inward/record.url?scp=85072296449&partnerID=8YFLogxK