A5060549482- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Space Science and Extraterrestrial Life
- Planetary Science and Exploration
- Geological and Geophysical Studies
- Calibration and Measurement Techniques
- Atmospheric Ozone and Climate
- Advanced Database Systems and Queries
- Global Energy and Sustainability Research
- Chemical Thermodynamics and Molecular Structure
- Astrophysics and Cosmic Phenomena
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Geological Studies and Exploration
- Nuclear Physics and Applications
- Adaptive optics and wavefront sensing
- Geological and Geochemical Analysis
- Computer Graphics and Visualization Techniques
- Data Management and Algorithms
- Semantic Web and Ontologies
University of Warwick
2015-2025
University of Sheffield
2021-2024
Centro de Estudios de Física del Cosmos de Aragón
2024
University of Trieste
2023
Max Planck Institute for Radio Astronomy
2016
Max Planck Society
2016
Monash University
2003
We present a catalogue of white dwarf candidates selected from the second data release Gaia (DR2). used sample spectroscopically confirmed dwarfs Sloan Digital Sky Survey (SDSS) to map entire space spanned by these objects in Hertzsprung–Russell diagram. then defined set cuts absolute magnitude, colour, and number quality flags remove majority contaminating objects. Finally, we adopt method analogous one presented our earlier SDSS photometric catalogues calculate probability being (PWD) for...
We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). applied several selection criteria in absolute magnitude, colour, and quality flags to remove objects with unreliable measurements while preserving most stars compatible the locus Hertzsprung-Russell diagram. then used sample over 30 000 spectroscopically confirmed dwarfs contaminants Sloan Digital Sky Survey (SDSS) map distribution these magnitude-colour space. Finally, we adopt same method...
White dwarfs (WDs) are powerful tools to study the evolutionary history of stars and binaries in Galaxy. But do we understand their multiplicity from a theoretical point view? This can be tested by comparison with sample WDs within 20 pc, which is minimally affected selection biases. From literature, compile available information local WD particular emphasis on multiplicity, compare this synthetic models formation single binaries. As part our population synthesis approach, also effect...
We present the first volume-limited sample of cataclysmic variables (CVs), selected using accurate parallaxes provided by second data release (DR2) ESA $\mathit{Gaia}$ space mission. The is composed 42 CVs within $150\,$pc, including two new systems discovered data, and $(77 \pm 10)\,$per cent complete. use this to study intrinsic properties Galactic CV population. In particular, density we derive, $\rho=(4.8^{+0.6}_{-0.8}) \times10^{-6}\,\mathrm{pc}^{-3}$, lower than predicted most binary...
In a previous study, we analysed the spectra of 230 cool ($T_\mathrm{eff}$ < 9000 K) white dwarfs exhibiting strong metal contamination, measuring abundances for Ca, Mg, Fe and in some cases Na, Cr, Ti, or Ni. Here interpret these terms accretion debris from extrasolar planetesimals, infer parent body compositions ranging crust-like (rich Ca Ti) to core-like Ni). particular, two dwarfs, SDSSJ0823+0546 SDSSJ0741+3146, which show log[Fe/Ca] > 1.9 dex, Ni ratios similar bulk Earth, have...
Using Gaia DR2 data, we present an up-to-date sample of white dwarfs within 20 pc the Sun. In total identified 139 systems in DR2, nine which are new detections, with closest these located at a distance 13.05 pc. We estimated atmospheric parameters for all stellar remnants based on parallaxes and photometry. The high precision completeness astrometry allowed us to search wide binary companions. re-identified known binaries where both components have accurate astrometry, established binarity...
We present an overview of the sample northern hemisphere white dwarfs within 40 pc Sun detected from $Gaia$ Data Release 2 (DR2). find that 521 sources are spectroscopically confirmed degenerate stars, 111 which were first identified as dwarf candidates DR2 and followed-up recently with William Herschel Telescope Gran Telescopio Canarias. Three additional remain unobserved six unresolved binaries known to include a but not in our initial selection Hertzsprung-Russell diagram (HRD)....
White dwarfs with metal lines in their spectra act as signposts for post-main-sequence planetary systems. Searching the Sloan Digital Sky Survey (SDSS) Data Release 12, we have identified 231 cool (<9000 K) DZ white strong absorption, extending cooling sequence to both higher abundances and lower temperatures, hence longer ages. Of these systems, 104 are previously unknown dwarfs. Compared previous work, our spectral fitting uses improved model atmospheres updated line profiles line-lists,...
A low-mass planet around a white dwarf Numerous exoplanets have been detected Sun-like stars. These stars end their lives as dwarfs, which should inherit any surviving planetary systems. Manser et al. found periodic shifts in emission lines from disc of gas orbiting (see the Perspective by Fossati). They used numerical simulations to show that most likely explanation for spectral is within disc. The must be unusually small and dense avoid being ripped apart tidal forces. authors speculate it...
ABSTRACT We present a comprehensive overview of volume-complete sample white dwarfs located within 40 pc the Sun, significant proportion which were detected in Gaia Data Release 3 (DR3). Our DR3 contains 1076 spectroscopically confirmed dwarfs, with just five candidates volume remaining unconfirmed (&gt; 99 per cent spectroscopic completeness). Additionally, 28 not our initial selection from DR3, most are unresolved binaries. use photometry and astrometry to determine uniform set dwarf...
We report on a comparison of spectroscopic analyses for hydrogen (DA) and helium atmosphere (DB) white dwarfs with Gaia Data Release 2 (DR2) parallaxes photometry. assume reddening law mass–radius relation to connect the effective temperatures (Teff) surface gravities (log g) masses radii. This allows two largely independent sets fundamental parameters 7039 DA 521 DB stars high-quality observations. subset dwarf sample is large enough detect systematic trends in derived parameters. find that...
We present a spectroscopic survey of 230 white dwarf candidates within 40 pc the Sun from William Herschel Telescope and Gran Telescopio Canarias. All were selected $\textit{Gaia}$ Data Release 2 (DR2) in almost all cases had no prior classifications. find total 191 confirmed dwarfs 39 main-sequence star contaminants. The majority stellar remnants sample are relatively cool ($\langle T_{\rm eff} \rangle$ = 6200 K), showing either hydrogen Balmer lines or featureless spectrum, corresponding...
Nine metal-polluted white dwarfs are observed with medium-resolution optical spectroscopy,where photospheric abundances determined and interpreted through comparison against solar system objects. An improved method of making such comparisons is presented that overcomes potential weaknesses prior analyses, the numerous sources error considered to highlight limitations on interpretation. The stars inferred be accreting rocky, volatile-poor asteroidal materials origins in differentiated bodies,...
Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, compositions accretion material dominantly from core (or mantle) a differentiated body. Collisions between exoplanetesimals produce such fragments. this work, we take advantage large numbers where at least one siderophile (core-loving) and lithophile (rock-loving) species been detected to assess how commonly differentiate. We utilise N-body simulations track fate...
1-3 per cent of white dwarfs are orbited by planetary dusty debris detectable as infrared emission in excess above the dwarf flux. In a rare subset these systems, gaseous disc component is also detected via lines Ca II 8600\r{A} triplet, broadened Keplerian velocity disc. We present first statistical study fraction discs containing amounts gas at within magnitude and signal-to-noise limited sample. select 7705 single spectroscopically observed Sloan Digital Sky Survey (SDSS) $Gaia$ with...
We present a spectroscopic survey of 248 white dwarf candidates within 40 pc the Sun; these 244 are in southern hemisphere. Observations were performed mostly with Very Large Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all selected from $\textit{Gaia}$ Data Release 3 (DR3). find total 246 confirmed dwarfs, 209 which had no previously published spectra, two main-sequence star contaminants. Of these, 100 dwarfs display hydrogen Balmer lines, 69 have featureless...
Magnetic white dwarfs with field strengths below 10 MG are easy to recognise since the Zeeman splitting of spectral lines appears proportional magnetic strength. For fields $\geq 100$ MG, however, transition wavelengths become chaotic, requiring quantum-chemical predictions and oscillator a non-perturbative treatment field. While highly accurate calculations have previously been performed for hydrogen helium, variational techniques employed computationally intractable systems more than three...
Little is known about the incidence of magnetic fields among coolest white dwarfs. Their spectra usually do not exhibit any absorption lines as bound–bound opacities hydrogen and helium are vanishingly small. Probing these stars for presence therefore extremely challenging. However, external pollution a cool dwarf by, e.g. planetary debris, leads to appearance metal in its spectral energy distribution. These provide unique tool identify measure magnetism oldest dwarfs Galaxy. We report...
We report the discovery of three stars that, along with prototype LP40-365, form a distinct class chemically peculiar runaway that are survivors thermonuclear explosions. Spectroscopy four confirmed LP 40-365 finds ONe-dominated atmospheres enriched remarkably similar amounts nuclear ashes partial O- and Si-burning. Kinematic evidence is consistent ejection from binary supernova progenitor; at least two have rest-frame velocities indicating they unbound to Galaxy. With masses radii ranging...
ABSTRACT The age–metallicity relation (AMR) is a fundamental tool for constraining the chemical evolution of Galactic disc. In this work, we analyse observational properties using binary stars that have not interacted consisting white dwarf (WD) – from which can derive total age system and main sequence (MS) star metallicity as traced by [Fe/H] abundances. Our sample consists 46 widely separated, but unresolved spectroscopic binaries identified within Sloan Digital Sky Survey, 189 WD plus MS...
We identify two ultra-cool ($T_\mathrm{eff} < 4000$ K) metal-polluted (DZ) white dwarfs WDJ2147$-$4035 and WDJ1922$+$0233 as the coolest second DZ stars known to date with $T_\mathrm{eff} \approx 3050$ K 3340$ K, respectively. Strong atmospheric collision-induced absorption (CIA) causes suppression of red optical infra-red flux in WDJ1922$+$0233, resulting an unusually blue colour given its low temperature. has moderate CIA yet reddest colours for a dwarf. Microphysics improvements non-ideal...
The ESA Gaia space mission has revealed a bifurcation of the white dwarf (WD) sequence on color magnitude diagram in two branches: A and B. While branch consists mostly WDs with H-rich atmospheres, B is not completely understood. Although invoked to be populated mainly by He-rich WDs, overlaps $\sim 0.8M_\odot$ evolutionary track pure He envelope, fact that would imply an unexpected peak WD mass distribution. In cold it expected outer convective zone penetrates into deep C-rich layers, thus...
ABSTRACT The accretion of tidally disrupted planetary bodies is the current consensus model for presence photospheric metals commonly detected in white dwarfs. While most dynamical studies have considered a single star and associated instabilities, several investigations instead influence widely bound stellar companions as potential drivers dwarf pollution. This study examines prevalence wide binaries among polluted dwarfs using Gaia Data Release 3 astrometry, where three samples are...
LP 40-365 (aka GD 492) is a nearby low-luminosity hyper-runaway star with an extremely unusual atmospheric composition, which has been proposed as the remnant of white dwarf that survived subluminous Type Ia supernova (SN Ia) in single-degenerate scenario. Adopting Gaia Data Release (DR2) parallax, 1.58 +/- 0.03 mas, we estimate radius 0.18 0.01 Rsun, confirming ~ 15 times larger than typical and compatible SN We present updated kinematic analysis, making use parallax proper motion, confirm...