A5045566915- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- High-pressure geophysics and materials
- Geophysics and Gravity Measurements
- Space Science and Extraterrestrial Life
- Planetary Science and Exploration
- Particle Accelerators and Free-Electron Lasers
- Advanced X-ray and CT Imaging
- Crystallography and Radiation Phenomena
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Pulsed Power Technology Applications
- Geophysics and Sensor Technology
- Space Satellite Systems and Control
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
University of Sheffield
2015-2025
Physical Sciences (United States)
2025
The mergers of binary compact objects such as neutron stars and black holes are central interest to several areas astrophysics, including the progenitors gamma-ray bursts (GRBs), sources high-frequency gravitational waves likely production sites for heavy element nucleosynthesis via rapid capture (the r-process). These elements include some great geophysical, biological cultural importance, thorium, iodine gold. Here we present observations exceptionally bright burst GRB 230307A. We show...
M dwarfs are prime targets in the hunt for habitable worlds around other stars. This is due to their abundance as well small radii and low masses temperatures, which facilitate detection of temperate, rocky planets orbit them. However, fundamental properties difficult constrain, often limiting our ability characterise they host. Here we test several theoretical relationships by measuring 23 high precision, model-independent binaries with white dwarfs. We find a large scatter these low-mass...
We present high precision, model independent, mass and radius measurements for 16 white dwarfs in detached eclipsing binaries combine these with previously published data to test the theoretical dwarf mass-radius relationship. reach a mean precision of 2.4 per cent 2.7 radius, our best reaching 0.3 0.5 radius. find excellent agreement between measured predicted radii across wide range masses temperatures. also all less than 0.48M$_\odot$ be fully consistent helium core models, but they are...
We present a search for optical bursts from the repeating fast radio burst FRB 121102 using simultaneous observations with high-speed camera ULTRASPEC on 2.4-m Thai National Telescope and 100-m Effelsberg Radio Telescope. A total of 13 were detected, but we found no evidence corresponding in our 70.7-ms frames. The 5-sigma upper limit to flux density during is 0.33 mJy at 767nm. This gives an fluence 0.046 Jy ms, which constrains broadband spectral index emission alpha < -0.2. Two pulses are...
We obtained high-speed photometry of the disintegrating planetesimals orbiting white dwarf WD1145+017, spanning a period four weeks. The light curves show dramatic evolution system since first observations about seven months ago. Multiple transit events are detected in every curve, which have varying durations(~3-12min) and depths (~10-60%). time-averaged extinction is ~11%, much higher than at time Kepler observations. shortest-duration transits require that occulting cloud debris has few...
We present measurements of the component masses in 15 Cataclysmic Variables (CVs) – 6 new estimates and 9 improved estimates. provide calibrations relationship between superhump period excess mass ratio, use this relation to estimate donor star for 225 superhumping CVs. With an increased sample we revisit implications CV evolution. confirm high white dwarfs CVs, but find no trend dwarf with orbital period. argue a revision location minimum CVs 79.6 ± 0.2 min, significantly shorter than...
HiPERCAM is a portable, quintuple-beam optical imager that saw first light on the 10.4-m Gran Telescopio Canarias (GTC) in 2018. The instrument uses re-imaging optics and 4 dichroic beamsplitters to record $u_s g_s r_s i_s z_s$ ($320-1060$ nm) images simultaneously its five CCD cameras, each of 3.1 arcmin (diagonal) field view. detectors are frame-transfer devices cooled thermo-electrically 183 K, thereby allowing both long-exposure, deep imaging faint targets, as well high-speed (over 1000...
We present a long-term programme for timing the eclipses of white dwarfs in close binaries to measure apparent and/or real variations their orbital periods. Our includes 67 binaries, both detached and semi-detached with M-dwarfs, K-dwarfs, brown or secondaries. In total, we have observed more than 650 dwarf eclipses. use this sample search period aim identify underlying cause these variations. find that probability observing increases significantly observational baseline. particular, all...
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...
We present optical photometry of the cataclysmic variable LAMOST J024048.51+195226.9 taken with high-speed, five-band CCD camera HiPERCAM on 10.4 m Gran Telescopio Canarias (GTC). detect pulsations originating from spin its white dwarf, finding a period 24.9328(38)s. The pulse amplitude is order 0.2% in g-band, below detection limits previous searches. This establishes as only second dwarf magnetic propeller system, twin long-known predecessor, AE Aquarii. At 24.93s, has shortest known any...
Wide-field time-domain photometric sky surveys are now finding hundreds of eclipsing white dwarf plus M binaries, a population encompassing wealth information and potential insight into close binary astrophysics. Precise follow-up observations essential in order to fully constrain these systems capitalise on the power this sample. We present first results from our program high-speed, multi-band follow-up. develop method measure temperatures, (model-dependent) masses, radii for both...
White dwarfs are often found in close binaries with stellar or even substellar companions. It is generally thought that these compact form via common envelope evolution, triggered by the progenitor of white dwarf expanding after it evolved off main-sequence and engulfing its companion. To date, a handful companions have been found, typically masses greater than around 50 M$_\mathrm{Jup}$. Here we report discovery two eclipsing plus brown containing very low mass dwarfs. ZTF J1828+2308...
Abstract White dwarfs are often found in close binaries with stellar or even substellar companions. It is generally thought that these compact form via common envelope evolution, triggered by the progenitor of white dwarf expanding after it evolved off main-sequence and engulfing its companion. To date, a handful companions have been found, typically masses greater than around 50 MJup. Here we report discovery two eclipsing plus brown containing very low mass dwarfs. ZTF J1828+2308 consists...
AM CVn-type systems are ultra-compact, hydrogen-deficient accreting binaries with degenerate or semi-degenerate donors. The evolutionary history of these can be explored by constraining the properties their donor stars. We present high-speed photometry Gaia14aae, an CVn a binary period 49.7 minutes and first in which central white dwarf is fully eclipsed star. Modelling lightcurves this system allows for most precise measurement to date mass CVn, relies only on geometric well-tested physical...
ABSTRACT The shortest-period binary star system known to date, RX J0806.3+1527 (HM Cancri), has now been observed in the optical for more than two decades. Although it is thought be a double degenerate undergoing mass transfer, an early surprise was that its orbital frequency, f0, currently increasing as result of gravitational wave radiation. This unusual since expected donor and would expand on loss, leading decreasing f0. We exploit decades high-speed photometry precisely quantify...
Ultracompact accreting binary systems each consist of a stellar remnant helium-enriched material from compact donor star. Such binaries include two related sub-classes, AM CVn-type and helium cataclysmic variables, in both which the central star is white dwarf. We present spectroscopic photometric study six with orbital periods range 40--70 min, including phase-resolved VLT spectroscopy high-speed ULTRACAM photometry. Four these are CVn variables. For four we able to identify (of three...
We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using H α images taken with 4.2-m William Herschel Telescope (WHT) and 2.5-m Isaac Newton Photometric Survey Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. concentrated our WHT nova-like variables, whilst IPHAS covered all CVs in footprint. found one shell out 24 we examined. The newly discovered is V1315 Aql has radius ∼2.5 arcmin, indicative eruption approximately 120 yr...
The majority of cataclysmic variable (CV) stars contain a stochastic noise component in their light curves, commonly referred to as flickering. This can significantly affect the morphology CV eclipses and increases difficulty obtaining accurate system parameters with reliable errors through eclipse modelling. Here we introduce new approach modelling, which models flickering help Gaussian processes (GPs). A parameterised model - an additional GP is simultaneously fit 8 dwarf nova ASASSN-14ag...
We present the discovery of SDSS J135154.46-064309.0, a short-period variable observed using 30-minute cadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed support classification as new member rare class ultracompact accreting binaries known AM CVn stars. The spectroscopic orbital period $15.65 \pm 0.12$\,minutes makes this system fourth-shortest known, second type to be discovered by Kepler spacecraft. data show photometric periods at $15.7306 0.0003$\,minutes,...
We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period 76.3 min, lies just below minimum ∼82 min for cataclysmic variable stars (CVs). Averaging four eclipses reveals resolved white and bright spot. determined system parameters by fitting a parametrized eclipse model to averaged light curve. obtain mass ratio q = 0.087 ± 0.006 inclination i 85|$_{.}^{\circ}$|2 0|$_{.}^{\circ}$|9. The primary donor masses were found be Mw 0.73 0.03...
AR Scorpii (AR Sco) is the only radio-pulsing white dwarf known to date. It shows a broad-band spectrum extending from radio X-rays whose luminosity cannot be explained by thermal emission system components alone, and instead through synchrotron powered spin-down of dwarf. We analysed NTT/ULTRACAM, TNT/ULTRASPEC, GTC/HiPERCAM high-speed photometric data for Sco spanning almost seven years obtained precise estimate spin frequency derivative, now confirmed with 50-sigma significance. Using...
We present the discovery of eclipsing double white dwarf (WD) binary WDJ 022558.21-692025.38 that has an orbital period 47.19 min. Following identification with Transiting Exoplanet Survey Satellite, we obtained time-series ground based spectroscopy and high-speed multi-band ULTRACAM photometry which indicate a primary DA WD mass 0.40 +- 0.04 Msol 0.28 0.02 secondary WD, is likely type as well. The system becomes third-closest discovered distance approximately 400 pc will be detectable...
Since 2006, the European Near Earth Asteroids Research (EURONEAR) project has been contributing to research of near-Earth asteroids (NEAs) within a network. One main aims is amelioration orbits NEAs, and starting in 2014 February we focus on recovery one-opposition NEAs using Isaac Newton Telescope (INT) La Palma override mode. Part this NEA project, since June EURONEAR serendipitously started discover secure first from INT, thanks teamwork including amateurs students who promptly reduce...