A5010287954- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Solar and Space Plasma Dynamics
- Scientific Computing and Data Management
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Space exploration and regulation
- Galaxies: Formation, Evolution, Phenomena
- Mathematics, Computing, and Information Processing
- Fluid Dynamics and Heat Transfer
- Computational Fluid Dynamics and Aerodynamics
- Inertial Sensor and Navigation
- Magnetic Bearings and Levitation Dynamics
- Geomagnetism and Paleomagnetism Studies
- Nonlinear Waves and Solitons
- Spacecraft Design and Technology
- Physics of Superconductivity and Magnetism
- Laser-Plasma Interactions and Diagnostics
Mount Allison University
2013-2023
University of California, Santa Barbara
2017
Los Alamos National Laboratory
2011-2014
Université de Versailles Saint-Quentin-en-Yvelines
2009-2012
Observatoire de Paris
2009-2012
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2009-2012
Sorbonne Université
2009-2012
Université Paris Cité
2009-2012
Délégation Paris 7
2012
Centre National de la Recherche Scientifique
2010-2012
The first stars are the key to formation of primitive galaxies, early cosmological reionization and chemical enrichment, origin supermassive black holes. Unfortunately, in spite their extreme luminosities, individual Population III (Pop III) will likely remain beyond reach direct observation for decades come. However, properties could be revealed by supernova explosions, which may soon detected a new generation near-IR (NIR) observatories such as JWST WFIRST. We present light curves spectra...
In this paper we introduce the MOBSTER collaboration and lay out its scientific goals. We present first results based on analysis of nineteen previously known magnetic O, B A stars observed in 2-minute cadence sectors 1 2 Transiting Exoplanet Survey Satellite (TESS) mission. derive precise rotational periods from newly obtained light curves compare them to published values. also discuss overall photometric phenomenology massive intermediate-mass propose an observational strategy augment...
We present simulations of the implosion a dense shell in two-dimensional (2D) spherical and cylindrical geometry performed with four different compressible, Eulerian codes: RAGE, FLASH, CASTRO, PPM. follow growth instabilities on inner face shell. Three codes employed Cartesian grid geometry, one (FLASH) polar geometry. While are similar, they employ advection algorithms, limiters, adaptive mesh refinement (AMR) schemes, interface-preservation techniques. find that rate instability is...
ABSTRACT We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 2 of TESS mission. utilize 2-min cadence data a sample 117 to classify their behaviour regarding variability place them Hertzsprung–Russell diagram using Gaia DR2 data. Included within our are eponymous members two pulsator classes, SX Phoenicis. Our pulsating intermediate-mass by also allows us confront theoretical models pulsation driving classical instability strip time show that...
Uncertainties in stellar structure and evolution theory are largest for stars undergoing core convection on the main sequence. A powerful way to calibrate free parameters used of interiors is asteroseismology, which provides direct measurements angular momentum element transport. We report detection classification new variable O B using high-precision short-cadence (2-min) photometric observations assembled by Transiting Exoplanet Survey Satellite (TESS). In our sample 154 stars, we detect a...
We use two-dimensional stellar models and a finite difference integration of the linearized pulsation equations to calculate nonradial oscillations. This approach allows us directly modes for distorted rotating star without treating rotation as perturbation. are also able express solution in horizontal direction sum multiple spherical harmonics any given mode. Using these methods, we have investigated effects increasing number on calculated eigenfrequencies eigenfunctions compared results...
The detection of Pop III supernovae could directly probe the primordial IMF for first time, unveiling properties galaxies, early chemical enrichment and reionization, seeds supermassive black holes. Growing evidence that some stars were less massive than 100 solar masses may complicate prospects their detection, because even though they would have been more plentiful died as core-collapse supernovae, with far luminosity pair-instability explosions. This picture greatly improves if SN shock...
ABSTRACT We present the results of a systematic search Transiting Exoplanet Survey Satellite (TESS) 2-min cadence data for new rapidly oscillating Ap (roAp) stars observed during Cycle 2 phase its mission. find seven roAp previously unreported as such and analysis further 25 that are already known. Three show multiperiodic pulsations, while all members rotationally variable stars, leading to almost 70 per cent (22) presented being α2 CVn-type stars. targeted observations known chemically...
Context. HD 181231 and 175869 are two late rapidly rotating Be stars, which have been observed using high-precision photometry with the CoRoT satellite during about five consecutive months 27 days, respectively. An analysis of their light curves, by Neiner collaborators Gutiérrez-Soto respectively, showed that several independent pulsation g-modes present in these stars. Fundamental parameters also determined authors spectroscopy.
HD49330 is a Be star that underwent an outburst during its five-month observation with the CoRoT satellite. An analysis of light curve revealed several independent p and g pulsation modes, in addition to showing amplitude modes directly correlated outburst. We modelled results obtained CoRoT. flattening structure due rapid rotation two ways: Chandrasekhar-Milne's expansion 2D computed ROTORC. then kappa-driven pulsations. also adapted formalism excitation stochastically excited...
We present the results of a systematic search for new rapidly oscillating Ap (roAp) stars using 2-min cadence data collected by Transiting Exoplanet Survey Satellite (TESS) during its Cycle 1 observations. identify 12 roAp stars. Amongst these we discover star with longest pulsation period, another shortest rotation and six multiperiodic variability. In addition to stars, an analysis 44 known observed TESS 1, providing first high-precision homogeneous sample significant fraction The...
We have investigated the effects of uniform rotation and a specific model for differential on pulsation frequencies 10 \Msun\ stellar models. Uniform decreases all modes. Differential does not appear to significant effect frequencies, except most extreme differentially rotating In cases, large small separations show at lower velocities than do individual frequencies. Unfortunately, certain extent, mimics o f more rapid rotation, only presence some observed with well identified modes will be...
Abstract We investigate the pulsation properties of stellar models that are representative δ Scuti and γ Doradus variables. have calculated a grid from 1.2 to 2.2 M ⊙ , including effects both rotation convective overshoot using MESA, we these GYRE. discuss observable patterns in frequency spacing for p modes period spacings g modes. Using mode spacings, it may be possible observationally constrain model. also calculate constant ( Q ) all our variation with rotation. The values radial can...
Extreme deformation of a stellar surface, such as that produced by rapid rotation, causes the surface temperature and gravity to vary significantly with latitude. Thus, spectral energy distribution (SED) nonspherical star could differ from SED spherical same average luminosity. Calculation deformed is often approximated composite several spectra, each plane-parallel model given effective gravity. The weighting these spectra over hence inferred luminosity, will be dependent on inclination...
Spectral energy distributions for models of arbitrarily rotating stars are computed using two-dimensional stellar models, NLTE plane-parallel model atmospheres, and a code to integrate the appropriately weighted intensities over visible surface disk. The spectral depend on inclination angle between observer rotation axis model. We use these curves deduce what one would infer model's luminosity effective temperature be assuming object was nonrotating.
Among the most spectacular variable stars are Luminous Blue Variables (LBVs), which can show three types of variability. The LBV phase evolution is poorly understood, and driving mechanisms for variability not known. common type variability, S Dor instability, occurs on timescales tens years. During an outburst, visual magnitude star increases, while bolometric stays approximately constant. In this work, we investigate pulsation as a possible trigger outbursts. We calculate pulsations...
(abridged) Recent work on several beta Cephei stars has succeeded in constraining both their interior rotation profile and convective core overshoot. In particular, a recent study focusing theta$ Oph shown that overshoot parameter of alpha = 0.44 is required to model the observed pulsation frequencies, significantly higher than for other this type. We investigate effects early type main sequence pulsators, attempt use low order frequencies constrain these parameters. This will be applied few...
AbstractThe Luminous Blue Variable stars exhibit behavior ranging from light curve 'microvariations' on timescales of tens days, to 'outbursts' accompanied by mass loss ~10−3 Msun occurring decades apart, 'giant eruptions' such as seen in Eta Carinae, ejecting one or more solar masses and recurring centuries. Here we review the work Los Alamos group since 1993, investigate pulsations instabilities massive using linear pulsation models non-linear hydrodynamic models. The predict pulsational...
BRITE-Constellation is devoted to high-precision optical photometric monitoring of bright stars, distributed all over the Milky Way, in red and/or blue passbands. Photometry from space avoids turbulent and absorbing terrestrial atmosphere allows for very long continuous observing runs with high time resolution thus provides data necessary understanding various processes inside stars (e.g., asteroseismology) their immediate environment. While first astronomical observations focused on...
Since the end of 2018, Transiting Exoplanet Survey Satellite (TESS) has provided stellar photometry to astronomical community. We have used TESS data study rotational modulation in light curves a sample chemically peculiar stars with measured large-scale magnetic fields (mCP stars). In general, mCP show inhomogeneous distributions elements their atmospheres that lead spectroscopic (line profile) and photometric (light curve) variations commensurate period. analyzed available from 50 sectors...
$\delta$ Orionis is the closest massive multiple stellar system and one of brightest members Orion OB association. The primary (Aa1) a unique evolved O star. In this work, we applied two-step disentangling method to series spectra in blue region (430 450 nm), detected spectral lines secondary (Aa2). For first time, were able constrain orbit tertiary (Ab) - 55 d or 152 yr using variable $\gamma$ velocities new speckle interferometric measurements, which have been published Washington Double...
Abstract δ Scuti variables are stars which exhibit periodic changes in their luminosity through radial and nonradial pulsations. Internally, these have relatively small convective cores, overshoot can significantly affect the size. Recently, models of pulsation found a strong correlation between constant ( Q ) as function effective temperature amount within star. However, only with metallicities Z = 0.02 were examined, leaving dependence of` this relationship on chemical composition unknown....
The new photometric data on pulsating Ap star HD~27463 obtained recently with the Transiting Exoplanet Survey Satellite (\textit{TESS}) are analysed to search for variability. Our analysis shows that exhibits two types of low frequency variability period $P$ =~2.834274 $\pm$ 0.000008 d can be explained in terms axial stellar rotation assuming oblique magnetic rotator model and presence surface abundance/brightness spots, while detected high-frequency variations characteristics $\delta$~Scuti...
ABSTRACT Luminous Blue Variables (LBVs) are massive stars that likely to be a transitionary phase between O and hydrogen-free classical Wolf–Rayet stars. The variability of these has been an area study for both professional amateur astronomers more than century. In this paper, we present 5 yr precision photometry the LBV P Cygni taken with BRITE-Constellation nanosatellites. We have analyzed data Fourier analysis search periodicities could elucidate drivers These show some long-time-scale...