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At least 163 records · Page 9
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NASA NTRS2020

Tidal Disruptions of Main-sequence Stars. IV. Relativistic Effects and Dependence on Black Hole Mass

Using a suite of fully relativistic hydrodynamic simulations applied to main-sequence stars with realistic internal density profiles, we examine full and partial tidal disruptions across a wide range of black hole mass (10(exp 5)≤M(BH)/M(ʘ)≤5 x 10(exp 7) and stellar mass (0.3≤M(*)/M(ʘ)≤3) as larger M(BH) leads to stronger relativistic effects. For fixed M( ), as M(BH) increases, the ratio of the maximum pericenter distance yielding full disruptions ( ) to its Newtonian prediction rises rapidly, becoming triple the Newtonian value for M(BH)=5 x 10(exp 7)M(ʘ), while the ratio of the energy width of the stellar debris for full disruptions to the Newtonian prediction decreases steeply, resulting in a factor of 2 correction at M(BH)=5 x 10(exp 7)M(ʘ). We provide approximate formulae that express the relativistic corrections of both R(t) and the energy width relative to their Newtonian approximate estimates. For partial disruptions, we find that the fractional remnant mass for a given ratio of the pericenter to R(t) is higher for larger M(BH). These results have several implications. As M(BH) increases above ~10(exp 7)M(ʘ), the cross section for complete disruptions is suppressed by competition with direct capture. However, the cross-section ratio for partial to complete disruptions depends only weakly on M(BH). The relativistic correction to the debris energy width delays the time of peak mass-return rate and diminishes the magnitude of the peak return rate. For M(BH)≳10(exp 7)M(ʘ), the M(BH)-dependence of the full disruption cross section and the peak mass-return rate and time is influenced more by relativistic effects than by Newtonian dynamics.

Taeho Ryu↗
NASA NTRS2020

On the Maximum Stellar Rotation to Form a Black Hole without an Accompanying Luminous Transient

The collapse of a massive star with low angular momentum content is commonly argued to result in the formation of a black hole without an accompanying bright transient. Our goal in this Letter is to understand the flow in and around a newly-formed black hole, involving accretion and rotation, via general relativistic hydrodynamics simulations aimed at studying the conditions under which infalling material can accrete without forming a centrifugally supported structure and, as a result, generate no effective feedback. If the feedback from the black hole is, on the other hand, significant, the collapse would be halted and we suggest that the event is likely to be followed by a bright transient. We find that feedback is only efficient if the specific angular momentum of the infalling material at the innermost stable circular orbit exceeds that of geodesic circular flow at that radius by at least≈20%. We use the results of our simulations to constrain the maximal stellar rotation rates of the disappearing massive progenitors PHL293B-LBV and N6946-BH1, and to provide an estimate of the overall rate of disappearing massive stars. We find that about a few percent of single O-type stars with measured rotational velocities are expected to spin below the critical value before collapse and are thus predicted to vanish without a trace.

Scott C Noble↗
NASA NTRS2020

Tidal Disruptions of Main Sequence Stars - I. Observable Quantities and their Dependence on Stellar and Black Hole Mass

This paper introduces a series of papers presenting a quantitative theory for the tidal disruption of main-sequence stars by supermassive black holes. Using fully general relativistic hydrodynamics simulations and MESA-model initial conditions, we explore the pericenter-dependence of tidal disruption properties for eight stellar masses(MM0.1510)and six black hole masses( MM105 105BH7). We present here the results most relevant to observations. The effects of internal stellar structure and relativity decouple for both the disruption cross section and the characteristic energy width of the debris. Moreover, the full disruption cross section is almost independent of Må for Må/Me3. Independent of Må, relativistic effects increase the critical pericenter distance for full disruption events by up to a factor of∼3 relative to the Newtonian prediction. The probability of a direct capture is also independent of Må; at MBH/Me;5×106 this probability is equal to the probability of a complete disruption. The breadth of the debris energy distribution ΔE can differ from the standard estimate by factors of0.35−2, depending on Må and MBH, implying a corresponding change(∝(ΔE)−3/2)in the characteristic mass-return timescale. We provide analytic forms, suitable for use in both event rate estimates and parameter inference, to describe all these trends. For partial disruptions, we find a nearly universal relation between the star’s angular momentum and the fraction of Må remaining. Within the “empty loss-cone” regime, partial disruptions must precede full disruptions. These partial disruptions can drastically affect the rate and appearance of subsequent total disruptions.

Taeho Ryu↗
NASA NTRS2020

Tidal Disruptions of Main-sequence Stars. IV. Relativistic Effects and Dependence on Black Hole Mass

Using a suite of fully relativistic hydrodynamic simulations applied to main-sequence stars with realistic internal density profiles, we examine full and partial tidal disruptions across a wide range of black hole mass( MM105 105BH7)and stellar mass (MM0.33) as larger MBH leads to stronger relativistic effects. For fixed Må, as MBH increases, the ratio of the maximum pericenter distance yielding full disruptions (t) to its Newtonian prediction rises rapidly, becoming triple the Newtonian value for= ́MM510BH7, while the ratio of the energy width of the stellar debris for full disruptions to the Newtonian prediction decreases steeply, resulting in a factor of 2 correction at= ́MM510BH7. We provide approximate formulae that express the relativistic corrections of both t and the energy width relative to their Newtonian approximate estimates. For partial disruptions, we find that the fractional remnant mass for a given ratio of the pericenter to t is higher for larger MBH. These results have several implications. As MBH increases above~M107, the cross section for complete disruptions is suppressed by competition with direct capture. However, the cross-section ratio for partial to complete disruptions depends only weakly on MBH. The relativistic correction to the debris energy width delays the time of peak mass-return rate and diminishes the magnitude of the peak return rate. ForMM10BH7, the MBH-dependence of the full disruption cross section and the peak mass-return rate and time is influenced more by relativistic effects than by Newtonian dynamics.

Taeho Ryu↗
NASA NTRS2020

Radiography in High Mass X-Ray Binaries: Micro-Structure of the Stellar Wind Through Variability of the Column Density

Context. In high mass X-ray binaries, an accreting compact object orbits a high mass star, which loses mass through a dense and in homogeneous wind. Aims. Using the compact object as an X-ray backlight, the time variability of the absorbing column density in the wind can be exploited in order to shed light on the micro-structure of the wind and obtain unbiased stellar mass-loss rates for high mass stars. Methods. We developed a simplified representation of the stellar wind where all the matter is gathered in spherical “clumps” that are radially advected away from the star. This model enables us to explore the connections between the stochastic properties of the wind and the variability of the column density for a comprehensive set of parameters related to the orbit and to the wind micro-structure, such as the size of the clumps and their individual mass. In particular, we focus on the evolution with the orbital phase of the standard deviation of the column density and of the characteristic duration of enhanced absorption episodes. Using the porosity length, we derive analytical predictions and compare them to the standard deviations and coherence time scales that were obtained. Results. We identified the favorable systems and orbital phases to determine the wind micro-structure. The coherence time scale of the column density is shown to be the self-crossing time of a single clump in front of the compact object. We thus provide a procedure to get accurate measurements of the size and of the mass of the clumps, purely based on the observable time variability of the column density. Conclusions. The coherence time scale grants direct access to the size of the clumps, while their mass can be deduced separately from the amplitude of the variability. We further show how monitoring the variability at superior conjunctions can probe the onset of the clump-forming region above the stellar photosphere. If the high column density variations in some high mass X-ray binaries are due to unaccreted clumps which are passing by the line-of-sight, this would require high mass clumps to reproduce the observed peak-to-peak amplitude and coherence time scales. These clump properties are marginally compatible with the ones derived from radiative-hydrodynamics simulations. Alternatively, the following components could contribute to the variability of the column density: larger orbital scale structures produced by a mechanism that has yet to be identified or a dense environment in the immediate vicinity of the accretor, such as an accretion disk, an outflow, or a spherical shell surrounding the magnetosphere of the accreting neutron star.

stars: mass loss↗
NASA NTRS2019

Deciphering the nature of the pulsar wind nebula CTB 87 with XMM-Newton

CTB 87 (G74.9+1.2) is an evolved supernova remnant (SNR) which hosts a peculiar pulsar wind nebula (PWN). The X-ray peak is offset from that observed in radio and lies towards the edge of the radio nebula. The putative pulsar, CXOU J201609.2+371110, was first resolved with Chandra and is surrounded by a compact and a more extended X-ray nebula. Here, we use a deep XMM–Newton observation to examine the morphology and evolutionary stage of the PWN and to search for thermal emission expected from a supernova shell or reverse shock interaction with supernova ejecta. We do not find evidence of thermal X-ray emission from the SNR and place an upper limit on the electron density of 0.05 per cu.cm for a plasma temperature kT ∼ 0.8 keV. The morphology and spectral properties are consistent with a ∼20-kyr-old relic PWN expanding into a stellar wind-blown bubble. We also present the first X-ray spectral index map from the PWN and show that we can reproduce its morphology by means of 2D axisymmetric relativistic hydrodynamical simulations.

B Guest↗
NASA NTRS2021

Atacama Cosmology Telescope: Combined kinematic and thermal Sunyaev-Zel’dovich measurements from BOSS CMASS and LOWZ halos

The scattering of cosmic microwave background (CMB) photons off the free-electron gas in galaxies and clusters leaves detectable imprints on high resolution CMB maps: the thermal and kinematic Sunyaev-Zel’dovich effects (tSZ and kSZ respectively). We use combined microwave maps from the Atacama Cosmology Telescope DR5 and Planck in combination with the CMASS (mean redshifthzi¼0.55and host halo masshMviri¼3×1013M⊙) and LOWZ (hzi¼0.31,hMviri¼5×1013M⊙) galaxy catalogs from the Baryon Oscillation Spectroscopic Survey (BOSS DR10 and DR12), to study the gas associated with these galaxy groups. Using individual reconstructed velocities, we perform a stacking analysis and reject the no-kSZ hypothes is at 6.5σ, the highest significance to date. This directly translates into a measurement of the electron number density profile, and thus of the gas density profile. Despite the limited signal to noise, the measurement shows at high significance that the gas density profile is more extended than the dark matter density profile, for any reasonable baryon abundance (formally>90σfor the cosmic baryon abundance). We simultaneously measure the tSZ signal, i.e., the electron thermal pressure profile of the same CMASS objects, and reject theno-tSZ hypothesis at10σ. We combine tSZ and kSZ measurements to estimate the electron temperature to20% precision in several aperture bins, and find it comparable to the virial temperature. In a companion paper, we analyze these measurements to constrain the gas thermodynamics and the properties of feedback inside galaxy groups. We present the corresponding LOWZ measurements in this paper, ruling out a null kSZ (tSZ)signal at 2.9ð13.9Þσ, and leave their interpretation to future work. This paper and the companion paper demonstrate that current CMB experiments can detect and resolve gas profiles in low mass halos and at high redshifts, which are the most sensitive to feedback in galaxy formation and the most difficult to measure any other way. They will be a crucial input to cosmological hydrodynamical simulations, thus improving our understanding of galaxy formation. These precise gas profiles are already sufficient to reduce the main limiting theoretical systematic in galaxy-galaxy lensing: baryonic uncertainties. Future such measurements will thus unleash the statistical power of weak lensing from the Rubin, Euclid and Roman observatories. Our stacking software Thumb Stack is publicly available and directly applicable to future Simons Observatory andCMB-S4 data.

Emmanuel Schaan↗
NASA NTRS2021

Modeling the Hydrodynamics, Sediment Transport, and Valley Incision of Outlet-forming Floods from Martian Crater Lakes

Open-basin lakes that have outlets, formed where the stored water breached the basin-confining topography (e.g., crater rims), have been recognized on Mars for decades. However, the mechanics involved in formation of these outlets has not been studied in detail. Here, we study this outlet formation process through a series of numerical experiments accomplished by adding erosion and sediment transport routines to an existing hydrodynamic simulation, ANUGA. These experiments are consistent with outlets being carved in single flood events, at least if sediment was available throughout outlet formation as in a transport-limited regime. Peak discharges from these open-basin lakes, including from Jezero crater, were 10^4–10^6 m^3/s, and the outlet-forming floods lasted for days to weeks, depending on lake size. Moreover, we find that sediment transport by suspension was likely important during these floods – outlets could not have reached their observed sizes if flow was limited to bedload transport alone. This in turn may explain why small open-basin lakes are less commonly recognized on Mars, as small lakes had less inherent capacity to transport sediment in suspension and thus incise confining topography catastrophically. Geometry, topographic setting, and earlier fluvial valley development may have played a significant role in influencing the magnitude of outlet-forming floods and resulting outlet canyon incision.

Mars↗
NASA NTRS2021

The Asymmetric Inner Disk of the Herbig Ae Star HD 163296 in the Eyes of VLTI/MATISSE: Evidence for a Vortex?

Context.A complex environment exists in the inner few astronomical units of planet-forming disks. High-angular-resolution observa-tions play a key role in our understanding of the disk structure and the dynamical processes at work.Aims.In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-massstar HD 163296 from early VLTI/MATISSE observations taken in theL- andN-bands. We put special emphasis on the detection ofpotential disk asymmetries.Methods.We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothedring, a flat disk with an inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetriesas well. We also perform numerical hydrodynamical simulations of the inner edge of the disk.Results.Our modeling reveals a significant brightness asymmetry in theL-band disk emission. The brightness maximum of the asym-metry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio inthe azimuthal variation is3.5±0.2. Comparing our result on the location of the asymmetry with other interferometric measurements,we confirm that the morphology of ther<0.3au disk region is time-variable. We propose that this asymmetric structure, located in ornear the inner rim of the dusty disk, orbits the star. To find the physical origin of the asymmetry, we tested a hypothesis where a vortexis created by Rossby wave instability, and we find that a unique large-scale vortex may be compatible with our data. The half-lightradius of theL-band-emitting region is0.33±0.01au, the inclination is52◦+5◦−7◦, and the position angle is143◦±3◦. Our models predictthat a non-negligible fraction of theL-band disk emission originates inside the dust sublimation radius forμm-sized grains. Refractorygrains or large (&10μm-sized) grains could be the origin of this emission.N-band observations may also support a lack of smallsilicate grains in the innermost disk (r.0.6au), in agreement with our findings fromL-band data.

J Varga↗
NASA NTRS2021

Tully-Fisher Distances and Dynamical Mass Constraints for 24 Host Galaxies of Reverberation-Mapped AGNs

We present Tully–Fisher distances for 24 active galactic nucleus (AGN) host galaxies with black hole mass (M(sub BH)) measurements from reverberation mapping, as well as the first calibration of the V-band Tully–Fisher relation. Combining our measurements of H I 21 cm emission with Hubble Space Telescope and ground-based optical and near-infrared images allows multiple distance measurements for 19 galaxies and single measurements for the remaining 5. Separation of the nucleus from its host galaxy via surface brightness decomposition yields galaxy-only luminosities, thus allowing measurements of the distance moduli free of contamination from the AGNs. For 14 AGN hosts, these are the first reported distances independent of redshift, and hence independent of peculiar velocities. For the remaining galaxies, we show good agreement between our distances and those previously reported from surface brightness fluctuations and Cepheids. We also determine the total galaxy mass enclosed within the estimated H I radius, which when compared to the baryonic content allows for constraints on the dark matter masses. We find a typical mass fraction of M(sub DM)/M(sub DYN) = 62%, and find significant correlations between M(sub BH)–M(sub DYN) and M(sub BH)–M(sub DM). Finally, we scale our galaxy radii based on estimated relationships between visible and halo radii and assume a flat rotation curve out to the halo radius to approximate M(sub HALO). Over the range of M(sub BH) and M(sub HALO) in this sample, we find good agreement with observationally constrained relationships between M(sub BH) and M(sub HALO) and with hydrodynamical simulations.

AGN host galaxies↗
NASA NTRS2021

Kozai–Lidov Oscillations Triggered by a Tilt Instability of Detached Circumplanetary Discs

Circumplanetary discs can be linearly unstable to the growth of disc tilt in the tidal potential of the star–planet system. We use3D hydrodynamical simulations to characterize the disc conditions needed for instability, together with its long-term evolution.Tilt growth occurs for disc aspect ratios, evaluated near the disc outer edge, ofH/r0.05, with a weak dependence on viscosityin the wave-like regime of warp propagation. Lower mass giant planets are more likely to have circumplanetary discs thatsatisfy the conditions for instability. We show that the tilt instability can excite the inclination to above the threshold where thecircumplanetary disc becomes unstable to Kozai–Lidov (KL) oscillations. Dissipation in the KL unstable regime caps furthertilt growth, but the disc experiences large oscillations in both inclination and eccentricity. Planetary accretion occurs in episodicaccretion events. We discuss implications of the joint tilt–KL instability for the detectability of circumplanetary discs, for theobliquity evolution of forming giant planets, and for the formation of satellite systems.

Rebecca G Martin↗
NASA NTRS2022

The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE

Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification. Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment. Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3–4 μm), M (4.5–5 μm), and N (8–13 μm) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with CO5BOLD and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively. Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration. Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr’s stellar surface and circumstellar environment across a very large spectral domain for the first time.

stars: atmospheres↗
NASA NTRS2020

Transition Region Contribution to AIA Observations in the Context of Coronal Heating

We investigate the ratio of coronal and transition region intensity in coronal loops observed by the AtmosphericImaging Assembly(AIA)on the Solar Dynamics Observatory(SDO). Using Enthalpy-based Thermal Evolution ofLoops(EBTEL)hydrodynamic simulations, we model loops with multiple lengths and energyfluxes heatedrandomly by events drawn from power-law distributions with different slopes and minimum delays between eventsto investigate how each of these parameters influences observable loop properties. We generate AIA intensitiesfrom the corona and transition region for each realization. The variations within and between models generatedwith these different parameters illustrate the sensitivity of narrowband imaging to the details of coronal heating.We then analyze the transition region and coronal emission from a number of observed active regions andfindbroad agreement with the trends in the models. In both models and observations, the transition region brightness issignificant, often greater than the coronal brightness in all six“coronal”AIA channels. We also identify an inverserelationship, consistent with heating theories, between the slope of the differential emission measure(DEM)coolward of the peak temperature and the observed ratio of coronal to transition region intensity. These resultshighlight the use of narrowband observations and the importance of properly considering the transition region ininvestigations of coronal heating

S J Schonfeld↗
NASA NTRSDate not supplied

Contribution to Solar Brightness of Small-Size Magnetic Elements

Irradiance variability is mostly driven by surface magnetism, each magnetic feature contributing in a different manner. The contribution of small-size magnetic elements observed ubiquitously at high-spatial resolution on the solar photosphere, is still debated, as such features are mostly unresolved on full-disk images employed to model irradiance variability. Understanding the contribution to solar brightness of small-size magnetic elements, especially in quiet regions, will help understanding irradiance variability on the decadal and longer temporal scales, which, in turn, are fundamental to understand the role of the Sun on the Earth’s climate. We present a preliminary study of the brightness of small-size magnetic elements using high-spatial resolution spectro-polarimetric observations acquired with the National Science Foundations Daniel K. Inouye Solar Telescope (DKIST) during Commissioning Phase 1. We focus on the Intensity contrast vs magnetic field relation, which is a fundamental observable in irradiance studies. Previous studies mostly focused on the FeI 630.1/630.2 nm spectral range and so to contextualize our results we focus here on this spectral region as well. By comparing DKIST results with MURaM magneto-hydrodynamic simulations, and with previous results published in the literature, we conclude that our results are in agreement with studies conducted on HINODE observations. We plan to extend the analysis to UV and IR ViSP observations and VBI blue continuum in order to better constrain the quiet sun contribution to spectral irradiance variations.

SMD↗
NASA NTRS2023

Prospects of Detecting Nonthermal Protons in Solar Flares via Lyman Line Spectroscopy: Revisiting the Orrall-Zirker Effect

Solar flares are efficient particle accelerators, with a substantial fraction of the energy released manifesting as nonthermal particles. While the role that nonthermal electrons play in transporting flare energy is well studied, the properties and importance of nonthermal protons are rather less well understood. This is in large part due to the paucity of diagnostics, particularly at the lower-energy (deka-keV) range of nonthermal proton distributions in flares. One means to identify the presence of deka-keV protons is by an effect originally described by Orrall & Zirker. In the Orrall–Zirker effect, nonthermal protons interact with ambient neutral hydrogen, and via charge exchange produce a population of energetic neutral atoms (ENAs) in the chromosphere. These ENAs subsequently produce an extremely redshifted photon in the red wings of hydrogen spectral lines. We revisit predictions of the strength of this effect using modern interaction cross sections, and numerical models capable of self-consistently simulating the flaring nonequilibrium ionization stratification, and the nonthermal proton distribution (and, crucially, their feedback on each other). We synthesize both the thermal and nonthermal emission from Ly α and Ly β, the most promising lines that may exhibit a detectable signal. These new predictions are weaker and more transient than prior estimates, but the effects should be detectable in fortuitous circumstances. We degrade the Ly β emission to the resolution of the Spectral Imaging of the Coronal Environment (SPICE) instrument on board Solar Orbiter, demonstrating that though likely difficult, it should be possible to detect the presence of nonthermal protons in flares observed by SPICE.

Solar flares↗
NASA NTRSDate not supplied

Comparison of Ring Diagrams Based on the Doppler Shifts of Synthetic Data Obtained with Bisector Method and SDO/HMI Pipeline

Ring diagrams are cross-sections of three-dimensional spatiotemporal power spectra of solar oscillations. The rings reveal information about sub-surface flows and represent an important tool for helioseismology. Ring diagrams can be constructed using Doppler velocity or intensity maps of spectral lines. How the velocities are computed is an important factor for accuracy of information we can retrieve on subsurface flows. In our work, the ring diagrams are generated from Doppler shift data of synthesized Fe I 6173 Å line. We compare ring diagrams computed by two methods–HMI line-of-sight pipeline and the bisector of Fe line. Fe I line is synthesized for StellarBox 3D Radiative hydrodynamic simulations under LTE assumption. We aim to answer the following questions: 1.How do power spectra obtained from velocities computed with the HMI pipeline and bisector of the Fe I 6173Å compare? 2.How do the power spectral density retrieved with each method vary with heliocentric angle? 3.What is the effect of changing resolution on the power spectral density in ring diagrams obtained with the two methods?

SMD↗
NASA NTRS2012

Improved Finite-Volume Method for Radiative Hydrodynamics

Fully coupled simulations of hydrodynamics and radiative transfer are essential to a number of fields ranging from astrophysics to engineering applications. Of particular interest in this work are hypersonic atmospheric entries and associated experimental apparatus, e.g., shock tubes and high enthalpy testing facilities. The radiative transfer calculations must supply to the CFD a heating term in the energy equation in the form of the divergence of the radiative heat flux and the radiative heat fluxes to bounding surfaces. It is most efficient to solve the radiative transfer equation on the same grid as the CFD solution, and this work presents an algorithm with improved accuracy for such simulations on structured and unstructured grids compared to more conventional approaches. Results will be shown for shock radiation during hypersonic reentry. Issues of parallelization within a radiation sweep will also be discussed.

Wray, Alan↗
NASA NTRS2015

Launch Environment Water Flow Simulations Using Smoothed Particle Hydrodynamics

This paper describes the use of Smoothed Particle Hydrodynamics (SPH) to simulate the water flow from the rainbird nozzle system used in the sound suppression system during pad abort and nominal launch. The simulations help determine if water from rainbird nozzles will impinge on the rocket nozzles and other sensitive ground support elements.

Smoothed Particle Hyrodynamics↗