S. L. Casewell
A5039035248- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Space Exploration and Technology
- Scientific Research and Discoveries
- Calibration and Measurement Techniques
- High-pressure geophysics and materials
- Space Science and Extraterrestrial Life
- Photocathodes and Microchannel Plates
- Astrophysics and Cosmic Phenomena
- Spacecraft Design and Technology
- Geomagnetism and Paleomagnetism Studies
- Transportation Planning and Optimization
- Geological and Geochemical Analysis
University of Leicester
2016-2025
NASA Exoplanet Science Institute
2023
Centre National de la Recherche Scientifique
2023
Centre National d'Études Spatiales
2023
Laboratoire d’Astrophysique de Marseille
2023
Aix-Marseille Université
2023
California Institute of Technology
2023
Ames Research Center
2023
University of California, Santa Cruz
2023
Université Grenoble Alpes
2023
We describe the Next Generation Transit Survey (NGTS), which is a ground-based project searching for transiting exoplanets orbiting bright stars. NGTS builds on legacy of previous surveys, most notably WASP, and designed to achieve higher photometric precision hence find smaller planets than have previously been detected from ground. It also operates in red light, maximizing sensitivity late K early M dwarf The survey specifications call 0.1 per cent light over an instantaneous field view...
Transmission spectroscopy1-3 of exoplanets has revealed signatures water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres4,5. However, these previous inferences with the Hubble Spitzer Space Telescopes were hindered by observations' relatively narrow wavelength range spectral resolving power, which precluded unambiguous identification other chemical species-in particular primary carbon-bearing molecules6,7. Here we report broad-wavelength 0.5-5.5 µm atmospheric...
Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking formation evolution exoplanetary systems. Access to an exoplanet's chemical inventory requires high-precision observations, often inferred from individual molecular detections with low-resolution space-based high-resolution ground-based facilities. Here we report medium-resolution (R$\sim$600) transmission spectrum atmosphere between 3-5 $\mu$m covering multiple absorption...
Transmission spectroscopy provides insight into the atmospheric properties and consequently formation history, physics, chemistry of transiting exoplanets. However, obtaining precise inferences from transmission spectra requires simultaneously measuring strength shape multiple spectral absorption features a wide range chemical species. This has been challenging given precision wavelength coverage previous observatories. Here, we present spectrum Saturn-mass exoplanet WASP-39b obtained using...
Abstract Close-in giant exoplanets with temperatures greater than 2,000 K (‘ultra-hot Jupiters’) have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from Hubble Space Telescope (HST) and Spitzer 1–3 . However, previous studies yielded inconsistent results because small sizes spectral features limited information content data resulted in high sensitivity varying assumptions made treatment instrument systematics retrieval...
Abstract Study Analysis Group 21 (SAG21) of NASA’s Exoplanet Exploration Program was organized to study the effect stellar contamination on space-based transmission spectroscopy, a method for studying exoplanetary atmospheres by measuring wavelength-dependent radius planet as it transits its star. Transmission spectroscopy relies precise understanding spectrum star being occulted. However, stars are not homogeneous, constant light sources but have temporally evolving photospheres and...
Abstract A complete accounting of nearby objects—from the highest-mass white dwarf progenitors down to low-mass brown dwarfs—is now possible, thanks an almost set trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census objects within Sun-centered sphere 20 pc radius check published literature decompose each binary or higher-order system into its separate components. The result is volume-limited ∼3600 individual star formation products...
The recent inference of sulfur dioxide (SO2) in the atmosphere hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations1-3 suggests that photochemistry is a key process high-temperature atmospheres4. This because low (<1 ppb) abundance SO2 under thermochemical equilibrium compared with produced H2O and H2S (1-10 ppm)4-9. However, was made single, small molecular feature transmission spectrum at 4.05 μm and, therefore, detection other absorption bands...
Abstract Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on nightside molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum hot Jupiter WASP-43b measured from 5 μm to 12 JWST’s Mid-Infrared Instrument. The spectra reveal large day–night temperature contrast (with...
The James Webb Space Telescope (JWST) presents the opportunity to transform our understanding of planets and origins life by revealing atmospheric compositions, structures, dynamics transiting exoplanets in unprecedented detail. However, high-precision, timeseries observations required for such investigations have unique technical challenges, prior experience with Hubble, Spitzer, other facilities indicates that there will be a steep learning curve when JWST becomes operational. In this...
We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host ($T_{eff}=3916^{+71}_{-63}~K$) in P=2.674d orbit discovered as part Next Generation Transit Survey (NGTS). The planet has mass $0.812^{+0.066}_{-0.075}~M_{J}$, making it most massive ever M-dwarf. radius is $1.33^{+0.61}_{-0.33}~R_{J}$. Since transit grazing, we determine this by modelling data and placing prior on density from population known gas giant planets. NGTS-1b third found around M-dwarf,...
We present the discovery and characterisation of two transiting planets observed by \textit{TESS} in light curves young bright (V=9.67) star HD73583 (TOI-560). perform an intensive spectroscopic photometric space- ground-based follow-up order to confirm characterise system. found that is a ($\sim 500$~Myr) active with rotational period $12.08 \pm 0.11 $\,d, mass radius $ 0.73 0.02 M_\odot$ $0.65 R_\odot$, respectively. b ($P_b=6.3980420 _{ - 0.0000062 }^{+0.0000067}$ d) has $10.2...
We report the discovery of NGTS-4b, a sub-Neptune-sized planet transiting 13th magnitude K-dwarf in 1.34d orbit. NGTS-4b has mass M=$20.6\pm3.0$M_E and radius R=$3.18\pm0.26$R_E, which places it well within so-called "Neptunian Desert". The mean density ($3.45\pm0.95$g/cm^3) is consistent with composition 100% H$_2$O or rocky core volatile envelope. likely to suffer significant loss due relatively strong EUV/X-ray irradiation. Its survival Neptunian desert may be an unusually high mass, have...
We present a series of systematic abundance measurements for 89 hydrogen atmosphere (DAtype) white dwarfs with temperatures spanning 16000-77000K drawn from the FUSE spectral archive.This is largest study to date where radiative forces are significant, exceeding our earlier work, based mainly on IUE and HST data, by factor three.Using heavy element blanketed non-LTE stellar calculations, we have addressed patterns making completely objective values their error ranges using χ 2 fitting...
The James Webb Space Telescope (JWST) is expected to revolutionize the field of exoplanets. broad wavelength coverage and high sensitivity its instruments will allow characterization exoplanetary atmospheres with unprecedented precision. Following Call for Cycle 1 Early Release Science Program, Transiting Exoplanet Community was awarded time observe several targets, including WASP-43b. atmosphere this hot Jupiter has been intensively observed but still harbors some mysteries, especially...
ABSTRACT NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds ), coronagraphic space mission to detect rocky planets habitable zones and establish their habitability. Surface liquid water central the definition of planetary Photometric polarimetric phase curves starlight reflected by an exoplanet can reveal ocean glint, rainbows, other phenomena caused scattering clouds or atmospheric gas. Direct imaging missions are optimized near quadrature, but HabWorlds ’ coronagraph...
Abstract Carbon monoxide was recently reported in the atmosphere of hot Jupiter WASP-39b using NIRSpec PRISM transit observation this planet, collected as part JWST Transiting Exoplanet Community Early Release Science Program. This detection, however, could not be confidently confirmed initial analysis higher-resolution observations with G395H disperser. Here we confirm detection CO data and cross-correlation techniques. We do by searching for signal unbinned transmission spectrum planet...
We present the discovery of fifteen new T2.5-T7.5 dwarfs (with estimated distances between ~24-93pc, identified in first three main data releases UKIRT Infrared Deep Sky Survey. This brings total number T discovered Large Area Survey (to date) to 28. These discoveries are confirmed by near infrared spectroscopy, from which we derive spectral types on unified scheme Burgasser et al. (2006). Seven have T2.5-T4.5, five T5-T5.5, one is a T6.5p, and two T7-7.5. assess morphology colours identify...
We present eight new T4.5-T7.5 dwarfs identified in the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area (LAS) Data Release 1 (DR1). In addition we have recovered T4.5 dwarf SDSS J020742.91+000056.2 and T8.5 ULAS J003402.77-005206.7. Photometric candidates were picked up two-colour diagrams over 190 square degrees (DR1) selected at least two filters. All exhibit near-infrared spectra with strong methane water absorption bands characteristic of T derived spectral types follow unified scheme...
A number of ultra-cool dwarfs emit circularly polarised radio waves generated by the electron cyclotron maser instability. In solar system such is emitted from regions strong auroral magnetic field-aligned currents. We thus apply ideas developed for Jupiter's magnetosphere, being a well-studied rotationally-dominated analogue in our system, to case fast-rotating UCDs. explain properties emission UCDs showing that it would arise electric currents resulting an angular velocity shear field and...
WD0137−349 is a white dwarf–brown dwarf binary system in 116 min orbit. We present radial velocity observations and multiwaveband photometry from V, R I the optical, to J, H Ks near-IR [3.6], [4.5], [5.8] [8.0] μm mid-IR. The light curves show variability all wavebands, with amplitude peaking at [4.5] μm, where also brightest. Fluxes brightness temperatures were computed for heated unheated atmosphere of brown (WD0137−349B) using synthetic spectra model simulations. that flux dayside...
Using data from the extended Kepler mission in K2 Campaign 10 we identify two eclipsing binaries containing white dwarfs with cool companions that have extremely short orbital periods of only 71.2 min (SDSS J1205-0242, a.k.a. EPIC 201283111) and 72.5 J1231+0041, 248368963). Despite their periods, both systems are detached small, low-mass companions, one case a brown dwarf, other either dwarf or star. We present follow-up photometry spectroscopy binaries, as well phase-resolved brighter...