A5033186532- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Calibration and Measurement Techniques
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- High-pressure geophysics and materials
- Atmospheric Ozone and Climate
- Advanced Chemical Physics Studies
- Molecular Spectroscopy and Structure
- Spacecraft and Cryogenic Technologies
- Spectroscopy and Laser Applications
- Infrared Target Detection Methodologies
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Advanced Thermodynamic Systems and Engines
- Dark Matter and Cosmic Phenomena
- demographic modeling and climate adaptation
- X-ray Spectroscopy and Fluorescence Analysis
University of Virginia
2024
McCormick (United States)
2024
University of Miami
2022-2023
South African Radio Astronomy Observatory
2012-2022
University of Cape Town
2017-2022
National Institute for Theoretical Physics
2017-2022
University of Bonn
2011-2014
University of Oxford
2010
Center for Astrophysics Harvard & Smithsonian
2005-2006
Harvard University
2003-2006
Carbon-enhanced metal-poor stars (CEMP) are observed as a substantial fraction of the very in Galactic halo. Most CEMP also enriched s-process elements and these often found binary systems. This suggests that carbon enrichment is due to mass transfer past from an asymptotic giant branch (AGB) star on low-mass companion. Models population synthesis not able reproduce without invoking non-standard nucleosynthesis or change initial function. interpreted evidence missing physical ingredients...
Abstract We present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed SPIRITS—SPitzer InfraRed Intensive Transients Survey. In the first year, using Spitzer /IRAC, we searched 190 nearby galaxies with cadence baselines of one month and six months. discovered over 1958 variables 43 transients. Here, describe survey design highlight 14 unusual transients no optical counterparts to deep limits, which refer as SPRITEs (eSPecially Red Intermediate-luminosity...
Interstellar bubbles around O stars are driven by a combination of the star's wind and ionizing radiation output. The contribution is uncertain because boundary between interstellar medium difficult to observe. Mid-infrared observations (e.g., H II region RCW 120) show arcs dust emission stars, contained well within bubble. These could indicate edge an asymmetric stellar bubble, distorted density gradients and/or motion. We present two-dimensional, radiation-hydrodynamics simulations...
We have mapped the 12CO(3–2) line emission around Mira AB system at 0.̋5 resolution using Atacama Large Millimeter/submillimeter Array (ALMA). The CO map shows amazing complexity. circumstellar gas has been shaped by different dynamical actors during evolution of system, and several morphological components can be identified. companion is marginally resolved in continuum currently 0.̋487 ± 0.̋006 separation. In main component, centered on stellar velocity, spiral arcs A are found. appears to...
Betelgeuse, the bright, cool red supergiant in Orion, is moving supersonically relative to local interstellar medium. The star emits a powerful stellar wind which collides with this medium, forming cometary structure, bow shock, pointing direction of motion. We present first 3D hydrodynamic simulations formation and evolution Betelgeuse's shock. models include realistic low temperature cooling cover range plausible medium densities velocities between 0.3 - 1.9 cm-3 28 73 km/s. show that flow...
Recent interpretations of narrow, variable absorption lines detected in some Type Ia supernovae suggest that their progenitors are surrounded by dense, circumstellar material. Similar variations the symbiotic recurrent nova system RS Oph, which undergoes thermonuclear outbursts every 20 years, making it an ideal candidate to investigate origin these lines. To this end, we present simulations multiple mass transfer-nova cycles Oph. We find quiescent transfer produces a equatorial outflow,...
We present a study of Hen 2-155 and 2-161, two planetary nebulae which bear striking morphological similarities to other known host close-binary central stars. Both stars are revealed be photometric variables while spectroscopic observations confirm that is double-eclipsing, post-common-envelope system with an orbital period 3h33m making it one the shortest binary known. The 2-161 found consistent ~1 day. A detailed model star 2-155, produced, showing nebular progenitor hot, post-AGB remnant...
Mid-infrared arcs of dust emission are often seen near ionizing stars within H ii regions. A possible explanations for these is that they could show the outer edges asymmetric stellar wind bubbles. We use two-dimensional, radiation-hydrodynamics simulations bubbles regions around individual to predict infrared properties region. assume and gas dynamically well-coupled (composition, size distribution) same in region as outside it, bubble contains no dust. post-process make synthetic intensity...
Abstract Detached, symbiotic binaries are generally assumed to interact via Bondi-Hoyle-Littleton (BHL) wind accretion. However, the accretion rates and outflow geometries that result from this mass-transfer mechanism cannot adequately explain observations of nearest best studied binary, Mira, or formation some post-AGB binaries, e.g. barium stars. We propose a new mode for Mira-type which we call ‘wind Roche-lobe overflow’ (WRLOF), demonstrate with 3D hydrodynamic simulations. Importantly,...
Context. Recent observations at subarcsecond resolution, now possible also submillimeter wavelengths, have shown intricate circumstellar structures around asymptotic giant branch (AGB) stars, mostly attributed to binary interaction. The results presented here are part of a larger project aimed investigating the effects companion on morphology envelopes (CSEs) AGB stars.
Abstract With upcoming missions such as the James Webb Space Telescope, European Extremely Large and Atmospheric Remote-sensing Infrared Exoplanet Large-survey, we soon will be on verge of detecting characterizing Earth-like exoplanetary atmospheres for first time. These planets are most likely to found around smaller cooler K- M-type stars. However, recent observations showed that their radiation environment might much harsher than Sun. Thus, exoplanets exposed an enhanced stellar...
Classical barium stars are binary systems which consist of a late-type giant enriched in carbon and slow neutron capture (s-process) elements an evolved white dwarf (WD) that is invisible at optical wavelengths. The youngest observed surrounded by planetary nebulae (PNe), ejected soon after the wind accretion polluted material when WD was its preceding asymptotic branch (AGB) phase. Such rare but powerful laboratories for studying AGB nucleosynthesis as we can measure chemical abundances...
A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption a binary system or ejection from their parent star cluster. The interaction wind with ISM produces bow shock. In late evolutionary stages these may undergo rapid transitions red blue and vice versa on Hertzsprung–Russell diagram, accompanying changes stellar winds shocks. Recent three-dimensional simulations shock produced by nearby runaway supergiant (RSG)...
We present near-infrared interferometry of the carbon-rich asymptotic giant branch (AGB) star R Sculptoris. The visibility data indicate a broadly circular resolved stellar disk with complex substructure. observed AMBER squared values show drops at positions CO and CN bands, indicating that these lines form in extended layers above photosphere. are best fit by model without wind. PIONIER consistent same model. obtain Rosseland angular diameter 8.9+-0.3 mas, corresponding to radius 355+-55...
Context. The S-type asymptotic giant branch (AGB) star π1 Gru has a known companion at separation of 2.̋7 (≈400 AU). Previous observations the circumstellar envelope (CSE) show strong deviations from spherical symmetry. structure, including an equatorial torus and fast bipolar outflow, is rarely seen in AGB phase particularly unexpected such wide binary system. Therefore second, closer been suggested, but evidence not conclusive.
We present a detailed study of the 2016 eruption nova V407 Lupi (ASASSN-16kt), including optical, near-infrared, X-ray, and ultraviolet data from SALT, SMARTS, SOAR, Chandra, Swift, XMM-Newton. Timing analysis multiwavelength light-curves shows that, 168 days post-eruption for duration X-ray supersoft source phase, two periods at 565 s 3.57 h are detected. suggest that these rotational period white dwarf orbital binary, respectively, system is likely to be an intermediate polar. The optical...
Herschel’s PACS instrument observed the environment of binary system Mira Ceti in 70 and 160 μm bands. These images reveal bright structures shaped as five broken arcs fainter filaments ejected material Mira’s primary star, famous AGB star o Ceti. The overall shape IR emission around deviates significantly from expected alignment with exceptionally high space velocity. are neither connected to each other nor they a circular shape; stretch over angular ranges 80 100 degrees. By comparing...
The CO(J=3-2) emission from the CSE of binary S-type AGB star W Aql has been observed at subarcsecond resolution using ALMA. aim this paper is to investigate wind properties and analyse how known companion shaped CSE. average mass-loss rate during creation detected estimated through modelling, ALMA brightness distribution previously published single-dish measurements as observational constraints. observations are presented compared results a 3D smoothed particle hydrodynamics (SPH)...
We report on multiwavelength observations of nova SMCN 2016-10a. The present observational set is one the most comprehensive for any in Small Magellanic Cloud, including: low, medium, and high resolution optical spectroscopy spectropolarimetry from SALT, FLOYDS, SOAR; long-term OGLE $V$- $I$- bands photometry dating back to six years before eruption; SMARTS near-IR $\sim$ 11 days until over 280 post-eruption; $Swift$ satellite X-ray ultraviolet 6 319 post-eruption. progenitor system contains...
By Fourier transform microwave spectroscopy, lambda-doubling transitions of 12 CH and 13 in the lowest rotational levels X 2 ∏ 1/2 ground state have been directly detected, which has not done previously. For both radicals, hyperfine-split lines measured to an accuracy better than 1 ppm between 3 15 GHz, improvement at least orders magnitude over previous laboratory data. The frequencies combined with all data for v = 0 level electronic determine improved hyperfine parameters. production from...