S. E. Woosley

Lawrence Berkeley National Laboratory, Berkeley, California, United States

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Publications (529)1870.39 Total impact

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    S. E. Woosley, Alexander Heger
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    ABSTRACT: The theory underlying the evolution and death of stars heavier than 10 Msun on the main sequence is reviewed with an emphasis upon stars much heavier than 30 Msun. These are stars that, in the absence of substantial mass loss, are expected to either produce black holes when they die, or, for helium cores heavier than about 35 Msun, encounter the pair instability. A wide variety of outcomes is possible depending upon the initial composition of the star, its rotation rate, and the physics used to model its evolution. These heavier stars can produce some of the brightest supernovae in the universe, but also some of the faintest. They can make gamma-ray bursts or collapse without a whimper. Their nucleosynthesis can range from just CNO to a broad range of elements up to the iron group. Though rare nowadays, they probably played a disproportionate role in shaping the evolution of the universe following the formation of its first stars.
    06/2014;
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    ABSTRACT: The kinetic energy of supernovae (SNe) accompanied by gamma-ray bursts (GRBs) tends to cluster near E52 erg, with 2.E52 erg an upper limit to which no compelling exceptions are found (assuming a certain degree of asphericity), and it is always significantly larger than the intrinsic energy of the GRB themselves (corrected for jet collimation). This energy is strikingly similar to the maximum rotational energy of a neutron star rotating with period 1 ms. It is therefore proposed that all GRBs associated with luminous SNe are produced by magnetars. GRBs that result from black hole formation (collapsars) may not produce luminous SNe. X-ray Flashes (XRFs), which are associated with less energetic SNe, are produced by neutron stars with weaker magnetic field or lower spin.
    06/2014;
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    ABSTRACT: Population III supernovae have been the focus of growing attention because of their potential to directly probe the properties of the first stars, particularly the most energetic events that can be seen at the edge of the observable universe. But until now pair-pulsation supernovae, in which explosive thermonuclear burning in massive stars fails to unbind them but can eject their outer layers into space, have been overlooked as cosmic beacons at the earliest redshifts. These shells can later collide and, like Type IIn supernovae, produce superluminous events in the UV at high redshifts that could be detected in the near infrared today. We present numerical simulations of a 110 M$_{\odot}$ pair-pulsation explosion done with the Los Alamos radiation hydrodynamics code RAGE. We find that collisions between consecutive pair pulsations are visible in the near infrared out to z $\sim$ 15 - 20 and can probe the earliest stellar populations at cosmic dawn.
    11/2013; 781(2).
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    ABSTRACT: We present high-resolution, full-star simulations of the post-ignition phase of Type Ia supernovae using the compressible hydrodynamics code Castro. Initial conditions, including the turbulent velocity field and ignition site, are imported directly from a simulation of the last few hours of presupernova convection using a low Mach number code, Maestro. Adaptive mesh refinement allows the initial burning front to be modeled with an effective resolution of 36,864^3 zones (~136 m/zone). The initial rise and expansion of the deflagration front are tracked until burning reaches the star's edge and the role of the background turbulence on the flame is investigated. The effect of artificially moving the ignition location closer to the star's center is explored. The degree to which turbulence affects the burning front decreases with increasing ignition radius since the buoyancy force is stronger at larger radii. Even central ignition --- in the presence of a background convective flow field --- is rapidly carried off-center as the flame is carried by the flow field. We compare our results to analytic models for burning thermals, and find that they reproduce the general trends of the bubble's size and mass, but underpredict the amount of buoyant acceleration due to simplifying assumptions of the bubble's properties. Overall, we find that the amount of mass that burns prior to flame break out is small, consistent with a "gravitationally confined detonation" occurring at a later epoch, but additional burning will occur following breakout that may modify this conclusion.
    09/2013; 782(1).
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    ABSTRACT: This work presents three-dimensional simulations of core convection in a 15 M ☉ star halfway through its main sequence lifetime. To perform the necessary long-time calculations, we use the low Mach number code MAESTRO, with initial conditions taken from a one-dimensional stellar model. We first identify several key factors that the one-dimensional initial model must satisfy to ensure efficient simulation of the convection process. We then use the three-dimensional simulations to examine the effects of two common modeling choices on the resulting convective flow: using a fixed composition approximation and using a reduced domain size. We find that using a fixed composition model actually increases the computational cost relative to using the full multi-species model because the fixed composition system takes longer to reach convection that is in a quasi-static state. Using a reduced (octant rather than full sphere) simulation domain yields flow with statistical properties that are within a factor of two of the full sphere simulation values. Both the octant and full sphere simulations show similar mixing across the convection zone boundary that is consistent with the turbulent entrainment model. However, the global character of the flow is distinctly different in the octant simulation, showing more rapid changes in the large-scale structure of the flow and thus a more isotropic flow on average.
    The Astrophysical Journal 08/2013; 773(2):137. · 6.73 Impact Factor
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    ABSTRACT: A leading model for Type Ia supernovae (SNe Ia) begins with a white dwarf near the Chandrasekhar mass that ignites a degenerate thermonuclear runaway close to its center and explodes. In a series of papers, we shall explore the consequences of ignition at several locations within such dwarfs. Here we assume central ignition, which has been explored before, however, the problem is worth revisiting, if only to validate those previous studies and to further elucidate the relevant physics for future work. A perturbed sphere of hot iron ash with a radius of ~100 km is initialized at the middle of the star. The subsequent explosion is followed in several simulations using a thickened flame model in which the flame speed is either fixed --- within the range expected from turbulent combustion --- or based on the local turbulent intensity. Global results, including the explosion energy and bulk nucleosynthesis (e.g. 56Ni of 0.48--0.56 $\Msun$) turn out to be insensitive to this speed. In all completed runs, the energy released by the nuclear burning is adequate to unbind the star, but not enough to give the energy and brightness of typical SNe Ia. As found previously, the chemical stratification observed in typical events is not reproduced. These models produce a large amount of unburned carbon and oxygen in central low velocity regions, which is inconsistent with spectroscopic observations, and the intermediate mass elements and iron group elements are strongly mixed during the explosion.
    The Astrophysical Journal 05/2013; 771(1). · 6.73 Impact Factor
  • Justin M. Brown, S. E. Woosley
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    ABSTRACT: Assuming a Salpeter initial mass function and taking the solar abundances as a representative sample, we explore the sensitivity of nucleosynthesis in massive stars to the truncation of supernova explosions above a certain mass. It is assumed that stars of all masses contribute to nucleosynthesis by their pre-explosive winds, but above a certain limiting main sequence mass, the presupernova star becomes a black hole and ejects nothing more. The solar abundances from oxygen to atomic mass 90 are fit quite well assuming no cut-off at all, i.e., by assuming all stars up to 120 solar masses make successful supernovae. Little degradation in the fit occurs if the upper limit is reduced to 25 solar masses. The limit can be further reduced, but the required event rate of supernovae in the remaining range rises rapidly to compensate for the lost nucleosynthesis of the more massive stars. The nucleosynthesis of the s-process declines precipitously and the production of species made in the winds, e.g., carbon, becomes unacceptably large compared with elements made in the explosion, e.g., silicon and oxygen. However, by varying uncertain physics, especially the mass loss rate for massive stars and the rate for the neon-22 to magnesium-25 reaction rate, acceptable nucleosynthesis might still be achieved with a cutoff as low as 18 solar masses. This would require a supernova frequency three times greater than the fiducial value obtained when all stars explode in order to produce the required oxygen-16. The nucleosynthesis of iron-60 and aluminum-26 is also examined.
    The Astrophysical Journal 02/2013; 769(2). · 6.73 Impact Factor
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    ABSTRACT: A diversity of models of SNIa have been presented in the literature, but all agree --- in one form or another --- that the event involves a thermonuclear explosion on or in the vicinity of a C/O white dwarf. Whether this explosion occurs as a deflagration, detonation, or both is somewhat of an open question, but all models ultimately must obtain the proper nucleosynthetic yields to reproduce the observed lightcurve and spectra. I describe some of the efforts of our group over the last few years involving the single degenerate, Chandrasekhar model. In particular, I describe our low Mach number MAESTRO simulations of the core convection and simmering that leads up to an off-center ignition. I also discuss how we have mapped these low Mach number results into our compressible hydrodynamics code, CASTRO, with a thickened flame model to evolve the ignition spot as it buoyantly rises toward the stellar surface. Upon breaking through the surface, the deflagration may transition to a detonation in regions of large shear or compression. The resulting explosion can then be put into a radiation hydrodynamic/transfer code to obtain synthetic spectra.
    01/2013;
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    ABSTRACT: The compactness of the core of a pre-supernova star is one of the important unexplored issues in progenitor evolution. Recent studies have found the core compactness to be varying non-monotonically as a function of ZAMS mass. In this work we have calculated a large grid of 1D full stellar and naked C/O core models using the implicit hydrodynamic code KEPLER and the open source stellar evolution code MESA, in order to gain a better insight in core compactness' dependence on the stellar mass and convection physics. We find the complicated evolution during C burning acts as the main cause of the non-monotonic variation of compactness, and the whole compactness curve as a function of mass to be quite dependent on the treatment of semiconvection. We also conclude that the C/O core mass is the main discriminant of pre-supernova structure.
    01/2013;
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    ABSTRACT: The first stars are the key to the formation of primitive galaxies, early cosmological reionization and chemical enrichment, and the origin of supermassive black holes. Unfortunately, in spite of their extreme luminosities, individual Population III stars will likely remain beyond the reach of direct observation for decades to come. However, their properties could be revealed by their supernova explosions, which may soon be detected by a new generation of NIR observatories such as JWST and WFIRST. We present light curves and spectra for Pop III pair-instability supernovae calculated with the Los Alamos radiation hydrodynamics code RAGE. Our numerical simulations account for the interaction of the blast with realistic circumstellar envelopes, the opacity of the envelope, and Lyman absorption by the neutral IGM at high redshift, all of which are crucial to computing the NIR signatures of the first cosmic explosions. We find that JWST will detect pair-instability supernovae out to z > 30, WFIRST will detect them in all-sky surveys out to z ~ 15 - 20 and LSST and Pan-STARRS will find them at z ~ 7 - 8. The discovery of these ancient explosions will probe the first stellar populations and reveal the existence of primitive galaxies that might not otherwise have been detected.
    The Astrophysical Journal 11/2012; · 6.73 Impact Factor
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    ABSTRACT: The first stars ended the cosmic Dark Ages and created the first heavy elements necessary for the formation of planets and life. The properties of these stars remain uncertain, and it may be decades before individual Pop III stars are directly observed. Their masses, however, can be inferred from their supernova explosions, which may soon be found in both deep-field surveys by JWST and in all-sky surveys by WFIRST. We have performed radiation hydrodynamical simulations of the near infrared signals of Pop III pair-instability supernovae in realistic circumstellar environments with Lyman absorption by the neutral intergalactic medium. We find that JWST and WFIRST will detect these explosions out to z ~ 30 and 20, respectively, unveiling the first generation of stars in the universe.
    The Astrophysical Journal Letters 09/2012; 762(1). · 6.35 Impact Factor
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    ABSTRACT: The first generation of stars in the universe may have been different from stars in the present-day universe. They may have been typically more massive than stars that form today, or may have rotated faster and hence their evolution, explosion, and overall nucleosynthesis yield could have been quite different. Theoretical models are needed to qualify and quantify these differences. Here we present nucleosynthesis results from the first generations of stars in the universe and how they may be connected to observed abundance patterns from ultra-metal poor stars.
    08/2012;
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    ABSTRACT: Cosmologists have used the light curves of Type Ia supernovae (SN Ia) as tools for surveying vast distances. Previous simulations have used coarse resolution and artificial initial conditions that substantially influenced their outcome. Here, we have the unique advantage of being able to import the results from previous simulations of convection leading to ignition from our low Mach number code, MAESTRO, directly into our compressible code, CASTRO. These initial conditions include the location of ignition and the turbulence on the grid. In this video, we show the turbulence within the early "bubble" of a supernova via renderings of the magnitude of the vorticity within the simulation. We then focus on the highest values of the magnitude of vorticity to observe the formation of "vortex tubes".
    High Performance Computing, Networking, Storage and Analysis (SCC), 2012 SC Companion:; 01/2012
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    ABSTRACT: We extend our previous three-dimensional, full-star simulations of the final hours of convection preceding ignition in Type Ia supernovae to higher resolution using the adaptive mesh refinement capability of our low Mach number code, MAESTRO. We report the statistics of the ignition of the first flame at an effective 4.34 km resolution, and general flow field properties at an effective 2.17 km resolution. We find that off-center ignition is likely, with radius of 50 km most favored and a likely range of 40 to 75 km. This is consistent with our previous coarser (8.68 km resolution) simulations, implying that we have achieved sufficient resolution in our determination of likely ignition radii. The dynamics of the last few hot spots preceding ignition suggest that a multiple ignition scenario is not likely. With improved resolution, we can more clearly see the general flow pattern in the convective region, characterized by a strong outward plume with a lower speed recirculation. We show that the convective core is turbulent with a Kolmogorov spectrum and has a lower turbulent intensity and larger integral length scale than previously thought (on the order of 16 km s$^{-1}$ and 200 km, respectively), and we discuss the potential consequences for the first flames.
    The Astrophysical Journal 11/2011; 745(1). · 6.73 Impact Factor
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    ABSTRACT: We present our end-to-end capability for computing the convective phase through the explosion phase of Type Ia supernovae. We compute the convective phase up to the time of ignition using our low Mach number code, MAESTRO, and the subsequent explosion phase using our compressible code, CASTRO. Both codes share the same BoxLib software framework and use finite-volume, block-structured adaptive mesh refinement (AMR) to enable high-resolution, three-dimensional full-star simulations that scale to 100,000+ cores. We present preliminary results from the first-ever simulations of convection preceding ignition using MAESTRO with AMR. We also demonstrate our ability to initialize a compressible simulation of the explosion phase in CASTRO using data obtained directly from MAESTRO just before ignition. Some care must be taken during this initialization procedure when interpreting the size and distribution of hot spots.
    11/2011;
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    S. E. Woosley, Alexander Heger
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    ABSTRACT: In the collapsar model for common gamma-ray bursts, the formation of a centrifugally supported disk occurs during the first $\sim$10 seconds following the collapse of the iron core in a massive star. This only occurs in a small fraction of massive stellar deaths, however, and requires unusual conditions. A much more frequent occurrence could be the death of a star that makes a black hole and a weak or absent outgoing shock, but in a progenitor that only has enough angular momentum in its outermost layers to make a disk. We consider several cases where this is likely to occur - blue supergiants with low mass loss rates, tidally-interacting binaries involving either helium stars or giant stars, and the collapse to a black hole of very massive pair-instability supernovae. These events have in common the accretion of a solar mass or so of material through a disk over a period much longer than the duration of a common gamma-ray burst. A broad range of powers is possible, $10^{47}$ to $10^{50}\,$erg s$^{-1}$, and this brightness could be enhanced by beaming. Such events were probably more frequent in the early universe where mass loss rates were lower. Indeed this could be one of the most common forms of gamma-ray transients in the universe and could be used to study first generation stars. Several events could be active in the sky at any one time. A recent example of this sort of event may have been the SWIFT transient Sw-1644+57.
    The Astrophysical Journal 10/2011; · 6.73 Impact Factor
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    A. J. Aspden, J. B. Bell, S Dong, S. E. Woosley
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    ABSTRACT: We develop a one-dimensional theoretical model for thermals burning in Type Ia supernovae based on the entrainment assumption of Morton, Taylor and Turner. Extensions of the standard model are required to account for the burning and for the expansion of the thermal due to changes in the background stratification found in the full star. The model is compared with high-resolution three-dimensional numerical simulations, both in a uniform environment, and in a full-star setting. The simulations in a uniform environment present compelling agreement with the predicted power-laws and provide model constants for the full-star model, which then provides excellent agreement with the full-star simulation. The importance of the different components in the model are compared, and are all shown to be relevant. An examination of the effect of initial conditions was then conducted using the one-dimensional model, which would have been infeasible in three dimensions. More mass was burned when the ignition kernel was larger and closer to the center of the star. The turbulent flame speed was found to be important during the early-time evolution of the thermal, but played a diminished role at later times when the evolution is dominated by the large-scale hydrodynamics responsible for entrainment. However, a higher flame speed effectively gave a larger initial ignition kernel and so resulted in more mass burned. This suggests that future studies should focus on the early-time behavior of these thermals (in particular, the transition to turbulence), and that the choice of turbulent flame speed does not play a significant role in the dynamics once the thermal has become established.
    The Astrophysical Journal 08/2011; 738(1). · 6.73 Impact Factor
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    A. J. Aspden, J. B. Bell, S. E. Woosley
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    ABSTRACT: In the distributed burning regime, turbulence disrupts the internal structure of the flame, and so the idea of laminar burning propagated by conduction is no longer valid. The nature of the burning depends on the turbulent Damkohler number (Da), which steadily declines from much greater than one to less that one as the density decreases to a few 10^6 g/cc. Scaling arguments predict that the turbulent flame speed s, normalized by the turbulent intensity u, follows s/u=Da^1/2 for Da<1. The flame in this regime is a single turbulently-broadened structure that moves at a steady speed, and has a width larger than the integral scale of the turbulence. The scaling is predicted to break down at Da=1, and the flame burns as a turbulently-broadened effective unity Lewis number flame. We refer to this kind of flame as a lambda-flame. The burning becomes a collection of lambda-flames spread over a region approximately the size of the integral scale. While the total burning rate continues to have a well-defined average, s_{T} ~ u, the burning is unsteady. We present a theoretical framework, supported by both 1D and 3D numerical simulations, for the burning in these two regimes. Our results indicate that the average value of s can actually be roughly twice u for Da>1, and that localized excursions to as much as five times u can occur. The lambda-flame speed and width can be predicted based on the turbulence in the star and the turbulent nuclear burning time scale of the fuel. We propose a practical method for measuring these based on the scaling relations and small-scale computationally-inexpensive simulations. This suggests that a simple turbulent flame model can be easily constructed suitable for large-scale distributed supernovae flames.
    The Astrophysical Journal 07/2011; 710. · 6.73 Impact Factor
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    A. J. Aspden, J. B. Bell, S. E. Woosley
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    ABSTRACT: In previous studies, we examined turbulence-flame interactions in carbon-burning thermonuclear flames in Type Ia supernovae. In this study, we consider turbulence-flame interactions in the trailing oxygen flames. The two aims of the paper are to examine the response of the inductive oxygen flame to intense levels of turbulence, and to explore the possibility of transition to detonation in the oxygen flame. Scaling arguments analogous to the carbon flames are presented and then compared against three-dimensional simulations for a range of Damk\"ohler numbers ($\Da_{16}$) at a fixed Karlovitz number. The simulations suggest that turbulence does not significantly affect the oxygen flame when $\Da_{16}<1$, and the flame burns inductively some distance behind the carbon flame. However, for $\Da_{16}>1$, turbulence enhances heat transfer and drives the propagation of a flame that is {\em narrower} than the corresponding inductive flame would be. Furthermore, burning under these conditions appears to occur as part of a combined carbon-oxygen turbulent flame with complex compound structure. The simulations do not appear to support the possibility of a transition to detonation in the oxygen flame, but do not preclude it either.
    The Astrophysical Journal 07/2011; 730(2). · 6.73 Impact Factor
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    S. E. Woosley
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    ABSTRACT: Most gamma-ray bursts are made during the deaths of massive stars. Here the environmental circumstances, stellar evolutionary paths, and explosion physics that might produce the bursts are reviewed. Neither of the two leading models - collapsar and millisecond magnetar - can be excluded, and both may operate in progenitor stars of different masses, metallicities, and rotation rates. Potential diagnostics are discussed and uncertainties highlighted. Both models are capable of producing a wide variety of transients whose properties vary with both stellar properties and viewing angle. Some of these are reviewed including the possibility of very long (days) low luminosity bursts, so far undiscovered, short hard bursts from massive stellar progenitors, and bursts from very massive Population III stars.
    05/2011;

Publication Stats

14k Citations
1,870.39 Total Impact Points

Institutions

  • 2011–2013
    • Lawrence Berkeley National Laboratory
      • Nuclear Science Division
      Berkeley, California, United States
  • 1970–2013
    • University of California, Santa Cruz
      • Department of Astronomy and Astrophysics
      Santa Cruz, California, United States
  • 2008–2010
    • Los Alamos National Laboratory
      • Theoretical Biology and Biophysics Group
      Los Alamos, California, United States
    • University of Washington Seattle
      • Institute for Nuclear Theory
      Seattle, WA, United States
    • California Institute of Technology
      • Division of Physics, Mathematics, and Astronomy
      Pasadena, California, United States
  • 2009
    • Stony Brook University
      • Department of Physics and Astronomy
      Stony Brook, NY, United States
  • 1996–2009
    • Max Planck Institute for Astrophysics
      Arching, Bavaria, Germany
  • 1998–2008
    • CSU Mentor
      Long Beach, California, United States
  • 2007
    • CUNY Graduate Center
      New York City, New York, United States
    • NASA
      Washington, West Virginia, United States
    • Monash University (Australia)
      • School of Mathematical Sciences, Clayton
      Melbourne, Victoria, Australia
  • 2006
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
    • IEEC Institute of Space Studies of Catalonia
      Barcino, Catalonia, Spain
    • University of Wyoming
      • Department of Physics and Astronomy
      Laramie, WY, United States
  • 1985–2006
    • Lawrence Livermore National Laboratory
      • Physics Division
      Livermore, California, United States
  • 2005
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
    • McGill University
      • Department of Physics
      Montréal, Quebec, Canada
    • Ecole normale supérieure de Lyon
      Lyons, Rhône-Alpes, France
  • 2004
    • University of Chicago
      Chicago, Illinois, United States
  • 1993–2004
    • Clemson University
      • Department of Physics and Astronomy
      Anderson, Indiana, United States
    • The University of Arizona
      Tucson, Arizona, United States
  • 1995–1999
    • University of California Observatories
      Santa Cruz, California, United States
  • 1992
    • San Francisco State University
      San Francisco, California, United States
  • 1986
    • Northwestern University
      Evanston, Illinois, United States
  • 1974
    • Rice University
      • Department of Physics and Astronomy
      Houston, Texas, United States