A5062100349- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- High-pressure geophysics and materials
- Galaxies: Formation, Evolution, Phenomena
- Fluid Dynamics and Turbulent Flows
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Scientific Measurement and Uncertainty Evaluation
- Aeolian processes and effects
- Gas Dynamics and Kinetic Theory
- Planetary Science and Exploration
- Computational Fluid Dynamics and Aerodynamics
- Combustion and flame dynamics
- Space Satellite Systems and Control
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Law, logistics, and international trade
University of Leeds
2013-2022
University of Sheffield
2022
University of Birmingham
1997-2009
Universidad Nacional de La Plata
2009
Royal Observatory of Belgium
2007-2009
University of Liège
2009
Osservatorio Astronomico di Palermo
2009
Instituto Argentino de Radioastronomía
2009
Herzberg Institute of Astrophysics
2007
Universidad Nacional Autónoma de México
2003
We present X-ray spectral fits to a recently obtained Chandra grating spectrum of η Carinae, one the most massive and powerful stars in Galaxy which is strongly suspected be colliding wind binary system. Hydrodynamic models winds are used generate synthetic spectra for range mass-loss rates velocities. They then fitted against newly acquired data. find that due low velocity primary (≈ ), observed emission appears arise from shocked companion star. use duration lightcurve minimum fix momentum...
We use 3D hydrodynamical models to investigate the effects of massive star feedback from winds and supernovae on inhomogeneous molecular material left over formation a stellar cluster. simulate interaction mechanical energy input cluster with three O-stars into giant cloud (GMC) clump containing 3240 M⊙ within 4 pc radius. The wind blows out along low-density channels, which denser is entrained. find that densest regions are surprisingly resistant ablation by wind, in part due shielding...
The Great Nebula in Carina provides an exceptional view into the violent massive star formation and feedback that typifies giant HII regions starburst galaxies. We have mapped star-forming complex X-rays, using archival Chandra data a mosaic of 20 new 60ks pointings X-ray Observatory's Advanced CCD Imaging Spectrometer, as testbed for understanding recent ongoing to probe Carina's bright diffuse emission. This study has yielded catalog properties >14,000 point sources; >9800 them...
We use hydrodynamical models of the wind-collision region in archetype colliding-wind system WR 140 to determine spatial and spectral distributions radio, X-ray, γ-ray emission from shock-accelerated electrons. Our calculations are for orbital phase 0.837 when observed radio is close maximum. Using thermal X-ray at this conjunction with constrain mass-loss rates, we find that O star rate consistent reduced estimates O4-5 supergiants by Fullerton, Massa & Prinja, wind-momentum ratio, η= 0.02....
Three dimensional (3D) adaptive-mesh refinement (AMR) hydrodynamical simulations of the wind-wind collision between enigmatic super-massive star \etacar and its mysterious companion are presented which include radiative driving stellar winds, gravity, optically-thin cooling, orbital motion. Simulations with static stars a periastron passage separation reveal that preshock star's wind speed is sufficiently reduced cooling in postshock gas becomes important, permitting runaway growth...
The X-ray emission from the supermassive star η Car is simulated using a 3D model of wind–wind collision. In intrinsic spatially extended and energy dependent. Absorption due to unshocked stellar winds cooled post-shock material primary LBV calculated as ray traced along multiple sightlines through spiral structure circumstellar environment. observable then compared available data, including light curve observed by Rossi Timing Explorer (RXTE) spectra XMM–Newton. orientation eccentricity...
ABSTRACT The key empirical property of the X-ray emission from O stars is a strong correlation between bolometric and luminosities. In framework Chandra Carina Complex Project, 129 B have been detected as sources; 78 those, all with spectral type earlier than B3, enough counts for at least rough characterization. This leads to an estimate L X – BOL ratio exceptional number 60 belonging same region triples massive studied spectroscopically in X-rays. derived log( / ) −7.26 single objects,...
MYStIX (Massive Young Star-Forming Complex Study in Infrared and Xray) seeks to characterize 20 OB-dominated young clusters their environs at distances d < 4 kpc using imaging detectors on the Chandra X-ray Observatory, Spitzer Space Telescope, United Kingdom InfraRed Telescope. The observational goals are construct catalogs of star-forming complex stellar members with well-defined criteria, maps nebular gas (particularly hot emitting plasma) dust. A catalog Probable Members (MPCMs) several...
The Chandra Carina Complex Project (CCCP) has shown that the Nebula displays bright, spatially-complex soft diffuse X-ray emission. Here, we "sum up" CCCP emission work by comparing global morphology and spectrum of Carina's to other famous sites massive star formation with pronounced emission: M17, NGC 3576, 3603, 30 Doradus. All spectral models require at least two thermal plasma components achieve adequate fits, a softer component kT = 0.2–0.6 keV harder 0.5–0.9 keV. In several cases...
The X-ray emission from the wind–wind collision in short-period massive O + star binaries is investigated. calculated 3D hydrodynamical models which incorporate gravity, driving of winds, orbital motion stars and radiative cooling shocked plasma. Changes amount stellar occultation circumstellar attenuation introduce phase-dependent variability systems with circular orbits, while strong variations intrinsic also occur eccentric orbits. can display hysteresis, softer after periastron than at...
The dynamics of the wind-wind collision in massive stellar binaries is investigated using three-dimensional hydrodynamical models which incorporate gravity, driving winds, orbital motion stars, and radiative cooling shocked plasma.In this first paper we restrict our study to main-sequence O+O binaries.The nature region highly dependent on degree plasma, ratio flow timescale plasma timescale.The pre-shock wind speeds are lower close systems as winds collide prior their acceleration terminal...
The interaction of a shock with cloud has been extensively studied in the literature, where effects magnetic fields, radiative cooling and thermal conduction have considered. However, formation fully developed turbulence often prevented by artificial viscosity inherent hydrodynamical simulations, uniform post-shock flow assumed all previous single-cloud studies. In reality, behind is also likely to be turbulent, non-uniform density, pressure velocity structure created as sweeps over...
NGC 3603 is the most massive and luminous visible starburst region in Galaxy. We present first Chandra ACIS-I X-ray image spectra of this dense, exotic object, accompanied by a deep centimeter-wavelength Australia Telescope Compact Array radio at similar ≲1'' spatial resolution Hubble Space Telescope/ground-based optical data. At S/N > 3 level, detects several hundred point sources (compared to three distinct seen ROSAT). least 40 these are definitely associated with optically identified...
We present calculations of the spatial and spectral distribution radio emission from a wide WR+OB colliding-wind binary system based on high-resolution hydrodynamical simulations solutions to radiative transfer equation. account for both thermal synchrotron emission, free-free absorption in unshocked stellar wind envelopes shocked gas, self-absorption, Razin effect. The applicability these modelling images spectra systems is demonstrated with models WR147. Its spectrum follows power-law...
We present a 3D dynamical model of the orbital induced curvature wind-wind collision region in binary star systems. Momentum balance equations are used to determine position and shape contact discontinuity between stars, while further downstream gas is assumed behave ballistically. An archimedean spiral structure formed by motion with clear resemblance high resolution images so-called ``pinwheel nebulae''. A key advantage this approach over grid or smoothed particle hydrodynamic models its...
We report the results of an X-ray observing campaign on massive, evolved star Eta Carinae, concentrating 2003 minimum as seen by XMM-Newton observatory. These are first spatially-resolved monitoring observations stellar spectrum during minimum. The hard emission, believed to be associated with collision Carinae's wind from a massive companion star, varied strongly in flux timescales days, but not significantly hours. lowest 2-10 keV band was only 0.7% maximum RXTE just before slope continuum...
We report continued monitoring of the superluminous binary system η Car by Proportional Counter Array on Rossi X-ray Timing Observatory (RXTE) through 2009 minimum. The RXTE campaign shows that minimum began January 16, consistent with phasings two previous minima, and overall, temporal behavior emission was similar to observed in cycles. However, important differences did occur. 2–10 keV flux hardness decreased 2.5 year interval leading up compared cycle. Most intriguingly, about 1 month...
We present a 1.42 deg2 mosaic of diffuse X-ray emission in the Great Nebula Carina from Chandra Observatory Advanced CCD Imaging Spectrometer camera. After removing >14,000 point sources field, we smooth remaining unresolved emission, tessellate it into segments similar apparent surface brightness, and perform spectral fitting on those tessellates to infer intrinsic properties X-ray-emitting plasma. By modeling faint resolved sources, estimate contribution extended show that vast majority...
We present the results from spectroscopic monitoring of WR 140 (WC7pd + O5.5fc) during its latest periastron passage in 2009 January. The observational campaign consisted a constructive collaboration between amateur and professional astronomers. It took place at six locations, including Teide Observatory, Observatoire de Haute Provence, Dominion Astrophysical Observatory du Mont Mégantic. is known as archetype colliding-wind binaries it has relatively long period (8 yr) high eccentricity...
We present 3D hydrodynamic simulations of the adiabatic interaction a shock with dense, spherical cloud. compare how nature changes Mach number shock, $M$, and density contrast cloud, $\chi$. examine differences 2D axisymmetric calculations, perform detailed resolution tests, "inviscid" results to those obtained inclusion $k$-$\epsilon$ subgrid turbulence model. Resolutions 32-64 cells per cloud radius are minimum necessary capture dominant dynamical processes in simulations, while inviscid...
Because of its key role in feedback star formation and galaxy formation, we examine the nature interaction a flow with discrete sources mass injection. We show results two-dimensional numerical simulations which explore range configurations for study effects their proximity on downstream flow. The act effectively as single source injection if they are so close together that ratio combined rate is comparable to or exceeds flux incident into volume occupy. relevant many diffuse sources, such...
Radio emission models of colliding wind binaries (CWBs) have been discussed by Dougherty et al. (2003). We extend these considering the temporal and spatial evolution energy distribution relativistic electrons as they advect downstream from their shock acceleration site. The spectrum evolves significantly due to strength inverse-Compton (IC) cooling in systems, a full numerical evaluation synchrotron absorption coefficients is made. demonstrated that geometry WCR streamlines flow within it...
The turbulent destruction of a cloud subject to the passage an adiabatic shock is studied. We find large discrepancies between lifetime and analytical result Hartquist et al. (1986). These differences appear be due assumption in that mass-loss occurs largely as lower pressure regions on surface away from stagnation point, whereas reality Kelvin-Helmholtz (KH) instabilities play dominant role destruction. true (defined when all material core well mixed with intercloud hydrodynamic cells)...
Context: Nonthermal radio emission in massive stars is expected to arise wind-wind collisions occurring inside a binary system. One such case, the O-type star Cyg OB2 #9, was proven be only four years ago, but orbital parameters remained uncertain. The periastron passage of 2011 first one observable under good conditions since discovery binarity. Aims: In this context, we have organized large monitoring campaign refine solution and study collision. Methods: This paper presents analysis...