A5021677314- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- CCD and CMOS Imaging Sensors
- Atmospheric Ozone and Climate
- Calibration and Measurement Techniques
- Scientific Research and Discoveries
- Galaxies: Formation, Evolution, Phenomena
University of Warwick
2018-2025
Abstract The DESI Legacy Imaging Surveys ( http://legacysurvey.org/ ) are a combination of three public projects (the Dark Energy Camera Survey, the Beijing–Arizona Sky and Mayall z -band Survey) that will jointly image ≈14,000 deg 2 extragalactic sky visible from northern hemisphere in optical bands g , r using telescopes at Kitt Peak National Observatory Cerro Tololo Inter-American Observatory. combined survey footprint is split into two contiguous areas by Galactic plane. imaging...
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...
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...
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 (> 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...
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...
We derive the local stellar formation history from Gaia-defined 40 pc white dwarf sample. This is currently largest volume-complete sample of dwarfs for which spectroscopy available, allowing classification chemical abundances at photosphere, and subsequently accurate determination atmospheric parameters. create a population synthesis model show that uniform last ~10.5 Gyr provides satisfactory fit to observed distribution absolute Gaia G magnitudes. To test robustness our derivation, we...
We compare three methods of deriving the local Galactic star formation history, using as a benchmark Gaia-defined 40 pc white dwarf sample, currently largest volume complete sample stellar remnants with medium-resolution spectroscopy. create population synthesis model to 1) reproduce observed luminosity function, 2) absolute Gaia G magnitude distribution, and 3) directly calculate ages all individual dwarfs in volume. then histories determined from each method. Previous studies these were...
Abstract We compare three methods of deriving the local Galactic star formation history, using as a benchmark Gaia-defined 40 pc white dwarf sample, currently largest volume complete sample stellar remnants with medium-resolution spectroscopy. create population synthesis model to (1) reproduce observed luminosity function, (2) absolute Gaia G magnitude distribution, and (3) directly calculate ages all individual dwarfs in volume. then histories determined from each method. Previous studies...
We present a study of the hypothesis that white dwarfs undergo spectral change from hydrogen- to helium-dominated atmospheres using volume-limited photometric sample drawn $Gaia$ DR2 catalogue, Sloan Digital Sky Survey (SDSS) and $Galaxy~Evolution~Explorer$ (GALEX). exploit strength Balmer jump in hydrogen-atmosphere DA separate them objects SDSS colour space. Across effective temperature range 20000K 9000K we find 22% will change, with no evolution being ruled out at 5$\sigma$. The most...
White dwarfs with metal-polluted atmospheres have been studied widely in the context of accretion rocky debris from evolved planetary systems. One open question is geometry and how material arrives mixes white dwarf surface layers. Using 3D radiation-hydrodynamics code CO$^5$BOLD, we present first transport coefficients degenerate star which describe advection-diffusion a passive scalar across surface-plane. We couple newly derived horizontal diffusion previously published vertical to...
We present the first grid of 3D simulations for pure-helium atmospheres DB white dwarfs. The were computed with CO5BOLD radiation-hydrodynamics code and cover effective temperatures surface gravities between 12000 K < Teff 34000 7.5 log(g) (cgs units) 9.0, respectively. In this introductory work, synthetic spectra calculated from are compared to appropriate 1D model under a differential approach. This results in derivation corrections spectroscopically derived atmospheric parameters stars...
In this paper, we present corrections to the spectroscopic parameters of DB and DBA white dwarfs with -10.0 < log(H/He) -2.0, 7.5 log(g) 9.0 12000 K T_eff 34000 K, based on 282 3D atmospheric models calculated CO5BOLD radiation-hydrodynamics code. These arise due a better physical treatment convective energy transport in when compared previously available 1D model atmospheres. By applying an existing SDSS sample dwarfs, find significant both for effective temperature surface gravity. The are...
We perform a calibration of the mixing length parameter at bottom boundary convection zone for helium-dominated atmospheres white dwarfs. This is based on grid 3D DB (pure-helium) and DBA (helium-dominated with traces hydrogen) model computed CO5BOLD code, 1D envelope structures. The models span space hydrogen-to-helium abundances between -10.0 -2.0, surface gravities 7.5 9.0 effective temperatures 12000 K 34000 K. envelopes cover similar atmospheric range, but are also calculated different...
We report the discovery of a detached double white dwarf binary with an orbital period $\approx20.6\,\rm minutes$, PTF J053332.05+020911.6. The visible object in this binary, J0533+0209B, is $\approx 0.17\,M_\odot$ mass helium-dominated atmosphere containing traces hydrogen (DBA). This exhibits ellipsoidal variations due to tidal deformation, and component single-lined spectroscopic velocity semi-amplitude $K_B=618.7\pm6.9 \, \rm km s^{-1}$. have detected significant decay emission...
The main objective of the present work is to extend these investigations by computing gravity and limb-darkening coefficients for white dwarf atmosphere models with hydrogen, helium, or mixed compositions (types DA, DB, DBA). We computed DBA dwarfs models, covering transmission curves Sloan, UBVRI, Kepler, TESS, Gaia photometric systems. Specific calculations HiPERCAM instrument were also carried out. For all we used least-squares method. Concerning effects tidal rotational distortions,...
We computed Doppler beaming factors for DA, DB, and DBA white dwarf models, as well main sequence giant stars covering the transmission curves of Sloan, UBVRI, HiPERCAM, Kepler, TESS, Gaia photometric systems. The calculations limb-darkening coefficients 3D models were carried out using least-squares method these factor calculations, which use realistic stellar atmospheres, show that black body approximation is not accurate, particularly filters $u$, $u'$, $U$, $g$, $g'$, $B$. approach only...
AM CVn binaries are a class of ultracompact, hydrogen-deficient binaries, each consisting white dwarf accreting helium-dominated material from degenerate or semi-degenerate donor star. Of the 56 known systems, only Gaia14aae undergoes complete eclipses its central dwarf, allowing parameters stellar components to be tightly constrained. Here, we present phase-resolved optical spectroscopy Gaia14aae. We use spectra test assumption that narrow emission feature as `central spike' traces motion...