High-contrast observations of brown dwarf companion HR 2562 B with the vector Apodizing Phase Plate coronagraph

InstrumentationStars and planetary system

Vector-apodizing phase plate coronagraph: design, current performance, and future development [Invited]

Instrumentatio

Bringing exoplanets into sharper view: Storm chasing on distant worlds

The planets of the Solar System possess cloud structures and weather systems with a great diversity of shapes, sizes, lifetimes, and brightnesses. As a planet rotates on its axis, these features rotate in and out of view and thereby induce changes in the total brightness of the planet as seen from afar. In this thesis, I develop new, bespoke techniques to look for similar brightness variability in the light curves of exoplanets and brown dwarfs, which can provide an insight into their weather, atmospheric structure, and visual appearance. Coronagraph-equipped ground-based observatories have the resolution and photon collecting power needed to monitor these faint, close-separation, companions, but lack access to the photometric references needed to correct for non-astrophysical variability introduced by turbulence in Earth's atmosphere. Uniquely, the vector Apodizing Phase Plate (vAPP) coronagraph enables observations of faint companions while maintaining an image of the host star for use as a photometric reference to remove contaminant variability. Using observations obtained with vAPP coronagraphs, I characterise the atmospheres of substellar companions and search for variability in their light curves. By combining the vAPP with an integral field spectrograph to enable differential spectrophotometry, I adapt concepts from the field of exoplanet transmission spectroscopy. I show that with the new techniques that I have developed we can reach 4% precision levels, repeatable on separate nights, and I highlight that improvements in wavefront sensing and systematics detrending could provide even greater precision, which will ultimately bring the features of distant worlds into sharper view

Bringing exoplanets into sharper view: Storm chasing on distant worlds

The planets of the Solar System possess cloud structures and weather systems with a great diversity of shapes, sizes, lifetimes, and brightnesses. As a planet rotates on its axis, these features rotate in and out of view and thereby induce changes in the total brightness of the planet as seen from afar. In this thesis, I develop new, bespoke techniques to look for similar brightness variability in the light curves of exoplanets and brown dwarfs, which can provide an insight into their weather, atmospheric structure, and visual appearance. Coronagraph-equipped ground-based observatories have the resolution and photon collecting power needed to monitor these faint, close-separation, companions, but lack access to the photometric references needed to correct for non-astrophysical variability introduced by turbulence in Earth's atmosphere. Uniquely, the vector Apodizing Phase Plate (vAPP) coronagraph enables observations of faint companions while maintaining an image of the host star for use as a photometric reference to remove contaminant variability. Using observations obtained with vAPP coronagraphs, I characterise the atmospheres of substellar companions and search for variability in their light curves. By combining the vAPP with an integral field spectrograph to enable differential spectrophotometry, I adapt concepts from the field of exoplanet transmission spectroscopy. I show that with the new techniques that I have developed we can reach 4% precision levels, repeatable on separate nights, and I highlight that improvements in wavefront sensing and systematics detrending could provide even greater precision, which will ultimately bring the features of distant worlds into sharper view

Applying a temporal systematics model to vector Apodizing Phase Plate coronagraphic data:TRAP4vAPP

Context. The vector Apodizing Phase Plate (vAPP) is a pupil plane coronagraph that suppresses starlight by forming a dark hole in its point spread function (PSF). The unconventional and non-axisymmetrical PSF arising from the phase modification applied by this coronagraph presents a special challenge to post-processing techniques. Aims. We aim to implement a recently developed post-processing algorithm, temporal reference analysis of planets (TRAP) on vAPP coronagraphic data. The property of TRAP that uses non-local training pixels, combined with the unconventional PSF of vAPP, allows for more flexibility than previous spatial algorithms in selecting reference pixels to model systematic noise. Methods. Datasets from two types of vAPPs are analysed: a double grating-vAPP (dgvAPP360) that produces a single symmetric PSF and a grating-vAPP (gvAPP180) that produces two D-shaped PSFs. We explore how to choose reference pixels to build temporal systematic noise models in TRAP for them. We then compare the performance of TRAP with previously implemented algorithms that produced the best signal-to-noise ratio (S/N) in companion detections in these datasets. Results. We find that the systematic noise between the two D-shaped PSFs is not as temporally associated as expected. Conversely, there is still a significant number of systematic noise sources that are shared by the dark hole and the bright side in the same PSF. We should choose reference pixels from the same PSF when reducing the dgvAPP360 dataset or the gvAPP180 dataset with TRAP. In these datasets, TRAP achieves results consistent with previous best detections, with an improved S/N for the gvAPP180 dataset