A5028503567- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Spacecraft and Cryogenic Technologies
- Spacecraft Design and Technology
- Innovative Teaching Methods
- Atmospheric Ozone and Climate
- Planetary Science and Exploration
- Calibration and Measurement Techniques
- Science Education and Pedagogy
- Diet, Metabolism, and Disease
- Biochemical effects in animals
- Experimental Learning in Engineering
- Space Exploration and Technology
- Space Satellite Systems and Control
Lowell Observatory
2015-2024
University of St Andrews
2011-2016
The Sun is the only star whose surface can be directly resolved at high resolution, and therefore constitutes an excellent test case to explore physical origin of stellar radial-velocity (RV) variability. We present HARPS observations sunlight scattered off bright asteroid 4/Vesta, from which we deduced Sun's activity-driven RV variations. In parallel, Helioseismic Magnetic Imager instrument on board Solar Dynamics Observatory provided us with simultaneous spatial resolution magnetograms,...
We present the results of a blind exercise to test recoverability stellar rotation and differential in Kepler light curves. The simulated curves lasted 1000 days included activity cycles, Sun-like butterfly patterns, spot evolution. range periods, levels lifetime were chosen be representative data solar like stars. Of curves, 770 injected into actual quiescent simulate noise. also five 1000-day segments Sun's total irradiance variations at different points cycle. Five teams took part...
By analogy with the solar system, it is believed that stellar winds will form bow shocks around exoplanets. For hot Jupiters shock not directly between planet and star, causing an asymmetric distribution of mass exoplanet hence transit. As orbits thorough varying wind conditions, strength geometry its change, thus producing transits shape. We model this process using magnetic maps HD 189733 taken one year apart, coupled a 3D model, to determine local conditions throughout orbital path...
Near ultraviolet observations of WASP-12b have revealed an early ingress compared to the optical transit lightcurve. This has been interpreted as due presence a magnetospheric bow shock which forms when relative velocity planetary and stellar material is supersonic. We aim reproduce this observed by modelling wind (or coronal plasma) in order derive speed density at orbital radius. From we determine orientation compressed plasma behind it. With model for structure surrounding planet perform...
HD189733 is an active K dwarf that is, with its transiting hot Jupiter, among the most studied exoplanetary systems. In this first paper of Multiwavelength Observations eVaporating Exoplanet and Star (MOVES) program, we present a 2-year monitoring large-scale magnetic field HD189733. The maps are reconstructed for five epochs observations, namely June-July 2013, August September 2014, July 2015, using Zeeman-Doppler Imaging. We show evolves along epochs, mean values total 36, 41, 42, 32 37...
We describe a collection of interactive animations and visualizations for teaching quantum mechanics. The can be used at all levels the undergraduate curriculum. Each animation includes step-by-step exploration that explains key points. instructor resources are freely available. By using diagnostic survey, we report substantial learning gains students who have worked with animations.
We present the discovery and characterisation of exoplanets WASP-113b WASP-114b by WASP survey, {\it SOPHIE} CORALIE}. The planetary nature systems was established performing follow-up photometric spectroscopic observations. data were combined with WASP-photometry analysed an MCMC code to obtain system parameters. host stars WASP-113 WASP-114 are very similar. They both early G-type effective temperature $\sim 5900\,$K, [Fe/H]$\sim 0.12$ $T_{\rm eff}$ 4.1$dex. However, is older than...
Abstract Bow shocks can be formed around planets due to their interaction with the coronal medium of host stars. The net velocity particles impacting on planet determines orientation shock. At Earth's orbit, (mainly radial) solar wind is primarily responsible for formation a shock facing towards Sun. However, close‐in that possess high Keplerian velocities and are frequently located at regions where star's still accelerating, may develop ahead planet. If compressed material able absorb...
In this third paper of the MOVES (Multiwavelength Observations an eVaporating Exoplanet and its Star) programme, we combine Hubble Space Telescope far-ultraviolet observations with XMM-Newton/Swift X-ray to measure emission HD 189733 in various FUV lines, soft spectrum. Based on these measurements characterise interstellar medium toward derive semi-synthetic XUV spectra star, which are used study evolution high-energy at five different epochs. Two flares from observed, but propose that...
We present stellar wind modelling of the hot Jupiter host HD189733, and predict radio emission from planet, latter arising interaction with planetary magnetosphere. Our models incorporate surface magnetic field maps at epochs Jun/Jul 2013, Sep 2014, Jul 2015 as boundary conditions. find that mass-loss rate, angular momentum-loss open flux HD189733 vary by 9%, 40%, 19% over these three epochs. Solving equations radiative transfer, we 10 MHz-100 GHz emits fluxes in range $10^{-3}$-$5$ $\mu$Jy,...
Transits of hot Jupiters in X-rays and the ultraviolet have been shown to be both deeper more variable than corresponding optical transits. This variability has attributed having extended atmospheres at these wavelengths. Using resolved images Sun from NASA's Solar Dynamics Observatory spanning 3.5 years Cycle 24 we simulate transit light curves a Jupiter investigate impact like activity on our ability reliably recover properties planet's atmosphere soft (94 {\AA}), UV (131-1700 (4500...
High-energy observations of the Sun provide an opportunity to test limits our ability accurately measure properties transiting exoplanets in presence stellar activity. Here we insert transits a hot Jupiter into continuous disk integrated data Lyman-alpha (Ly$\alpha$) from NASA's SDO/EVE instrument assess impact activity on measured planet-to-star radius ratio $(\textrm{R}_\textrm{p}/\textrm{R}_\star)$. In 75% simulated light curves correct ratio; however, incorrect values can be if there is...
Magnetic interactions between stars and close-in planets may lead to a detectable signal on the stellar disk. HD 189733 is one of key exosystems thought harbor magnetic interactions, which have been detected in August 2013. We present set twelve wind models at that period, covering possible coronal states topologies time. assess power available for interaction predict its temporal modulation. By comparing predicted with observed signal, we find some could be compatible an interpretation...
Abstract Planetary transits provide a unique opportunity to investigate the surface distributions of star spots. Our aim is determine if, with continuous observation (such as data that will be provided by Kepler mission), we can in addition measure rate drift spot belts. We begin simulating magnetic cycles suitable for Sun and more active stars, incorporating both flux emergence transport. This provides radial field distribution on stellar function time. then model transit planet whose...
A combination band due to a mechanism whereby photon excites two or more vibrational modes ({\it e.g.} bend and stretch) of an individual molecule is commonly seen in laboratory astronomical spectroscopy. Here, we present evidence much less $-$ one where simultaneously adjacent molecules ice. In particular, near-infrared spectra CO/N$_2$ ice samples identify at 4467.5 cm$^{-1}$ (2.239 $\mu$m) that results from single photons exciting pairs CO N$_2$ molecules. We also spectrum Neptune's...
ABSTRACT We report on the discovery and validation of a two-planet system around bright (V = 8.85 mag) early G dwarf (1.43 R⊙, 1.15 M⊙, TOI 2319) using data from NASA’s Transiting Exoplanet Survey Satellite (TESS). Three transit events two planets were detected by citizen scientists in month-long TESS light curve (sector 25), as part Planet Hunters project. Modelling transits yields an orbital period $11.6264 _{ - 0.0025 } ^ { + 0.0022 }$ d radius $3.41 0.12 0.14 R⊕ for inner planet, range...
The most extended, closed magnetic loops inferred on T Tauri stars confine hot, X-ray-emitting plasma at distances from the stellar surface beyond X-ray-bright corona and large-scale field, comparable to corotation radius. Mechanical equilibrium models have shown that dense condensations, or ‘slingshot prominences’, can rise great heights due their density temperatures cooler than environs. On stars, however, we detect hotter ambient coronal temperature. By previous model results, these...
ABSTRACT We present radial velocity measurements of the very bright (V ∼ 5.7) nearby F star, DMPP-4 (HD 184960). The anomalously low Ca ii H&K emission suggests mass-loss from planets orbiting a activity host star. Periodic variability with ∼10 m s−1 amplitude is found to persist over >4 yr time-scale. Although non-simultaneous photometric in four TESS sectors supports view an inactive we identify periodic signals and also find spectroscopic evidence for stellar activity. used...
The {\it Transiting Exoplanet Survey Satellite} (TESS) searches for planets transiting bright and nearby stars using high-cadence, large-scale photometric observations. Full Frame Images provided by the TESS mission include large number of serendipitously observed main-belt asteroids. Due to cadence published we are sensitive periods as long order tens days, a region phase space that is generally not accessible through traditional observing. This work represents much less biased measurement...
Coronal mass ejections (CMEs) are a prominent contributor to solar system space weather and might have impacted the Sun's early angular momentum evolution. A signal diagnostic of CMEs on Sun is coronal dimming: drop in emission, tied CME, that direct result removing emitting plasma from corona. We present results dimming analysis Fe XII 1349 XXI 1354 emission $ε$ Eridani ($ε$ Eri), young K2 dwarf, with archival far-ultraviolet observations by Hubble Space Telescope's Cosmic Origins...
Seventy-five billion low-mass stars in our galaxy host at least one small planet their habitable zone (HZ). The stellar ultraviolet (UV) radiation received by the planets is strong and highly variable, has consequences for atmospheric loss, composition, habitability. SPARCS a NASA-funded mission to characterize quiescent flare UV emission from stars, observing 10 20 over timescales of days, simultaneously two bands: 153-171 nm 260-300 nm. Sun-synchronous terminator orbit allows long periods...