A5026734533- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Ionosphere and magnetosphere dynamics
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Geomagnetism and Paleomagnetism Studies
- Astronomical Observations and Instrumentation
- Radio Astronomy Observations and Technology
- Spacecraft Design and Technology
- Astrophysical Phenomena and Observations
- Solar Radiation and Photovoltaics
- Global Energy and Sustainability Research
- Atmospheric Ozone and Climate
- Geophysics and Gravity Measurements
- SAS software applications and methods
- Nuclear Physics and Applications
- Historical Astronomy and Related Studies
- Masonry and Concrete Structural Analysis
- Calibration and Measurement Techniques
- Historical and Architectural Studies
- Economic Growth and Productivity
- Fluid Dynamics and Turbulent Flows
- Magnetic Bearings and Levitation Dynamics
Smithsonian Astrophysical Observatory
2017-2022
Center for Astrophysics Harvard & Smithsonian
2017-2021
Harvard University Press
2020
KU Leuven
2014-2017
Royal Belgian Institute for Space Aeronomy
2015-2016
National and Kapodistrian University of Athens
2012
In this paper we present an update on the open source MPI-AMRVAC simulation toolkit where focus solar- and non-relativistic astrophysical magneto-fluid dynamics. We highlight recent developments in terms of physics modules such as hydrodynamics with dust coupling conservative implementation Hall magnetohydrodynamics. A simple high-order finite difference scheme that works combination all available is introduced demonstrated at example monotonicity preserving fifth order reconstruction....
Recently, four additional Earth-mass planets were discovered orbiting the nearby ultracool M8 dwarf TRAPPIST-1, making a remarkable total of seven with equilibrium temperatures compatible presence liquid water on their surface. Temperate terrestrial around an M-dwarf orbit close to parent star, rendering atmospheres vulnerable erosion by stellar wind and energetic electromagnetic particle radiation. Here, we use state-of-the-art 3D magnetohydrodynamic models simulate TRAPPIST-1 study...
We present results from a set of numerical simulations aimed at exploring the mechanism coronal mass ejection (CME) suppression in active stars by an overlying large-scale magnetic field. use state-of-the-art 3D magnetohydrodynamic (MHD) code which considers self-consistent coupling between Alfv\'en wave-driven stellar wind solution, and first-principles CME model based on eruption flux-rope anchored to mixed polarity region. By replicating driving conditions used strong solar CMEs, we show...
Observations of young open clusters show a bimodal distribution rotation periods that has been difficult to explain with existing stellar spin-down models. Detailed MHD wind simulations have demonstrated surface magnetic field morphology strong influence on wind-driven angular momentum loss. suggest faster rotating stars store larger fraction their flux in higher-order multipolar components the field. In this work, we present new model for that, first time, accounts configuration. We how...
We report the results of first state-of-the-art numerical simulations Coronal Mass Ejections (CMEs) taking place in realistic magnetic field configurations moderately active M-dwarf stars. Our analysis indicates that a clear, novel, and observable, coronal response is generated due to collapse eruption its eventual release into stellar wind. Escaping CME events, weakly suppressed by large-scale field, induce flare-like signature emission from material at different temperatures compression...
Abstract Coronal mass ejections (CMEs) on stars other than the Sun have proven very difficult to detect. One promising pathway lies in detection of type II radio bursts. Their appearance and distinctive properties are associated with development an outward propagating CME-driven shock. However, dedicated searches not been able identify these transient features stars. Large Alfvén speeds magnetic suppression CMEs active proposed render stellar eruptions “radio-quiet.” Employing 3D...
Planets in close proximity to their parent star, such as those the habitable zones around M dwarfs, could be subject particularly high doses of particle radiation. We have carried out test-particle simulations ~GeV protons investigate propagation energetic particles accelerated by flares or travelling shock waves within stellar wind and magnetic field a TRAPPIST-1-like system. Turbulence was simulated with small-scale magnetostatic perturbations an isotropic power spectrum. find that only...
Solar CMEs and flares have a statistically well defined relation, with more energetic X-ray corresponding to faster massive CMEs. How this relation extends magnetically active stars is subject of open research. Here, we study the most probable stellar CME candidates associated captured in literature date, all which were observed on stars. We use simple model derive masses kinetic energies from quantities, transform flare data GOES 1--8~\AA\ band. Derived range $\sim 10^{15}$ $10^{22}$~g....
Abstract Stellar wind and photon radiation interactions with a planet can cause atmospheric depletion, which may have potentially catastrophic impact on planet’s habitability. While planetary atmospheres outflows been researched to some degree, studies of stellar are in their infancy. Here, we use three-dimensional magnetohydrodynamic simulations model the effect magnetosphere outflow hypothetical planet, modeled an H-rich evaporating envelope prescribed mass-loss rate, orbiting habitable...
One of the most important problems in context cataclysmic variables (CVs) is lack observations systems with periods between 2 and 3.12 hours, known as period gap. The orbital evolution CVs shorter than those gap dominated by gravitational radiation while for exceeding it magnetic braking secondary star. Spruit & Ritter (1983) showed that approach 3 hours stars become fully convective a sharp decline dynamo efficiency would result such Recent X-ray finding coronal energy dissipation similar...
Abstract Physics-informed neural networks (PINNs) are machine learning models that integrate data-based with partial differential equations (PDEs). In this work, for the first time we extend PINNs to model numerically challenging case of astrophysical shock waves in presence a stellar gravitational field. Notably, suffer from competing losses during gradient descent can lead poor performance especially physical setups involving multiple scales, which is shocks gravitationally stratified...
A new planet has been recently discovered around Proxima Centauri. With an orbital separation of $\sim$$1.44$ au and a minimum mass about $7$ $M_{\oplus}$, c is prime direct imaging target for atmospheric characterization. The latter can only be performed with good understanding the space environment planet, as multiple processes have profound effects on structure evolution. Here, we take one step in this direction by generating physically-realistic numerical simulations Proxima's stellar...
Abstract We explore the scenario of a coronal mass ejection (CME) being cause observed continuous X-ray absorption 1997 August 30 superflare on eclipsing binary Algol (the Demon Star). The temporal decay is consistent with by CME undergoing self-similar evolution uniform expansion velocity. investigate kinematic and energetic properties using ice cream cone model for its three-dimensional structure in combination profile hydrogen column density decline time. Different physically justified...
A former member of the Hyades cluster, ι Horologii (ι Hor) is a planet-hosting Sun-like star which displays shortest coronal activity cycle known to date (Pcyc ∼ 1.6 yr). With an age ∼625 Myr, Hor also youngest with detected cycle. The study its magnetic properties holds potential provide fundamental information understand origin cyclic and stellar magnetism in late-type stars. In this series papers, we present results comprehensive project aimed at studying evolving field how evolution...
Abstract The search for exoplanets in the radio bands has been focused on detecting emissions produced by interaction between magnetized planets and stellar wind (auroral emission). Here we introduce a new tool, which is part of our MHD corona model, to predict ambient coronal emission its modulations induced close planet. For simplicity, present work assumes that exoplanet stationary frame rotating with rotation. We explore flux using limited parameter space idealized cases changing...
We investigate the space environment conditions near Earth-size planet TOI~700~d using a set of numerical models for stellar corona and wind, planetary magnetosphere, ionosphere. drive our simulations scaled-down input scaled-up solar in order to obtain two independent solutions. find that particular parameters used study, wind are not very extreme -- slightly stronger than Earth terms ram pressure intensity interplanetary magnetic field. Thus, TOI700-d may be extremely harmful atmosphere,...
Abstract Cepheids are pulsating variable stars with a periodic chromospheric response at UV wavelengths close to their minimum radius phase. Recently, an X-ray signature was captured in observations during the maximum This emission came as surprise and is not understood. In this work, we use modern astrophysical code PLUTO investigate effects of pulsations on Cepheid emission. We run number hydrodynamic numerical simulations variety initial boundary conditions order explore capability shocks...
Abstract A physically realistic stellar wind model based on Alfvén wave dissipation has been used to simulate the from Barnard’s Star and estimate conditions at location of its recently discovered planetary companion. Such models require knowledge surface magnetic field that is currently unknown for Star. We circumvent this by considering observed distributions three different stars constitute admissible proxies object. Under these considerations, b experiences less intense pressure than...
Radio observations grant access to a wide range of physical processes through different emission mechanisms. These from thermal and quiescent eruptive phenomena, such as shock waves particle beams. We present new synthetic radio imaging tool that calculates visualizes the Bremsstrahlung emission. This works concurrently with state-of-the-art Magnetohydrodynamic (MHD) simulations solar corona using code BATS-R-US. Our model produces results are in good agreement both high low frequency disk....
V473 Lyr is a classical Cepheid which unique in having substantial amplitude variations with period of approximately 3.3 years, thought to be similar the Blazhko RR Lyrae stars. We obtained an {\it XMM-Newton} observation this star followup previous detection X-rays. Rather than X-ray burst and rapid decline near maximum radius seen $\delta$ Cephei itself, flux remained constant for third pulsation cycle covered by observation. Thus X-rays are most probably not produced changes around cycle....
Abstract X-ray bursts have recently been discovered in the Cepheids δ Cep and β Dor modulated by pulsation cycle. We obtained an observation of Cepheid η Aql with XMM-Newton satellite at phase maximum radius; which there is a burst X-rays Cep. No were seen from this phase, implications for upper atmospheres are discussed. also used combination sources, as well Gaia 2MASS data, to search possible grouping around young intermediate mass Cepheid. indication such group was found.