I am a PhD student in the extrasolar planets group at QUB. During this time, I have developed and led the QUB secondary eclipse campaign. Its main aim has been to observe the secondary eclipses of exoplanets using both photometry and spectroscopy at wavelengths not routinely covered by Hubble and Spitzer observations and to show the continuing relevance of relatively small, ground-based facilities in the age of JWST. Our observations of KELT-9b, the hottest known exoplanet, constitute the first published ground-based observation of the secondary eclipse of any exoplanet in the UV (see below). Our i-band eclipse measurements of WASP-12b disagree significantly, leaving the tantalising possibility that this is due to variability in its atmosphere. Our results for other targets including HAT-P-1b, KELT-16b and WASP-103b will be published in the near future.
I am also involved in the Next Generation Transit Survey (NGTS), which aims to discover Neptunes and super-Earths around stars with Vmag < 13.
KELT-9b is a recently discovered exoplanet with a 1.49 day orbit around a B9.5/A0-type star. The unparalleled levels of ultraviolet irradiation that it receives from its host star put KELT-9b in its own unique class of ultra-hot Jupiters, with an equilibrium temperature > 4000 K. The high quantities of dissociated hydrogen and atomic metals present in the dayside atmosphere of KELT-9b bear more resemblance to a K-type star than a gas giant. We present a single observation of KELT-9b during its secondary eclipse, taken with the Wide Field Camera on the Isaac Newton Telescope (INT). This observation was taken in the U-band, a window particularly sensitive to Rayleigh scattering. We do not detect a secondary eclipse signal, but our 3σ upper limit of 181 ppm on the depth allows us to constrain the dayside temperature of KELT-9b at pressures of ∼30 mbar to 4995 K (3σ). Although we can place an observational constraint of Ag < 0.14, our models suggest that the actual value is considerably lower than this due to H- opacity. This places KELT-9b squarely in the albedo regime populated by its cooler cousins, almost all of which reflect very small components of the light incident on their daysides. This work demonstrates the ability of ground-based 2 m class telescopes like the INT to perform secondary eclipse studies in the near-ultraviolet, which have previously only been conducted from space-based facilities.
Storms or Systematics? The Changing Secondary Eclipse Depth of WASP-12b - MNRAS (submitted)
WASP-12b is one of the most well-studied transiting exoplanets, as its highly-inflated radius and its 1.1 day orbit around a G0-type star make it an excellent target for atmospheric categorisation through observation during its secondary eclipse. We present two new secondary eclipse observations of WASP-12b, acquired with the Wide Field Camera on the Isaac Newton Telescope (INT) and the IO:O instrument on the Liverpool Telescope (LT). These observations were conducted in the i-band, a window expected to be dominated by TiO features if present in appreciable quantities in the upper atmosphere. We measured eclipse depths that disagree by ~3σ (1.02 ± 0.15 mmag on the INT and 0.44 ± 0.21 mmag on the LT), a result that is mirrored in previous z'-band secondary eclipse measurements for WASP-12b. We explore explanations for these disagreements, including systematic errors and variable thermal emission in the dayside atmosphere of WASP-12b caused by temperature changes of a few hundred Kelvin: a possibility we cannot rule out from our analysis. Full-phase curves observed with TESS and CHEOPS have the potential to detect similar atmospheric variability for WASP-12b and other optimal targets, and a strategic, multi-telescope approach to future ground-based secondary eclipse observations is required to discriminate between explanations involving storms and systematics.
NGTS-2b: An inflated hot-Jupiter transiting a bright F-dwarf - MNRAS, 481, 4960
We report the discovery of NGTS-2b, an inflated hot-Jupiter transiting a bright F5V star (2MASS J14202949-3112074; Teff= 6478+94−89 K), discovered as part of the Next Generation Transit Survey (NGTS). The planet is in a P=4.51 day orbit with mass 0.74+0.13−0.12 MJ, radius 1.595+0.047−0.045 RJ and density 0.226+0.040−0.038 g cm−3; therefore one of the lowest density exoplanets currently known. With a relatively deep 1.0% transit around a bright V=10.96 host star, NGTS-2b is a prime target for probing giant planet composition via atmospheric transmission spectroscopy. The rapid rotation (v sin i=15.2 ± 0.8 km s,−1) also makes this system an excellent candidate for Rossiter-McLaughlin follow-up observations, to measure the sky-projected stellar obliquity. NGTS-2b was confirmed without the need for follow-up photometry, due to the high precision of the NGTS photometry.