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in creator/contributor: "Torres, D."

open access

Theoretical Modelling of the Diffuse Emission of (gamma)-rays From Extreme Regions of Star Formation: The Case of Arp 220

Our current understanding of ultraluminous infrared galaxies suggest that they are recent galaxy mergers in which much of the gas in the former spiral disks, particularly that located at distances less than 5 kpc from each of the pre-merger nuclei, has fallen into a common center, triggering a huge starburst phenomenon. This large nuclear concentration of molecular gas has been detected by many groups, and estimates of molecular mass and density have been made. Not surprisingly, these estimates… more

Date: July 9, 2004

Creator: Torres, D F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A New Strong Field Effect in Scalar-Tensor Gravity: Spontaneous Violation of the Energy Conditions

A decade ago, it was shown that a wide class of scalar-tensor theories can pass very restrictive weak field tests of gravity and yet exhibit non-perturbative strong field deviations away from General Relativity. This phenomenon was called 'Spontaneous Scalarization' and causes the (Einstein frame) scalar field inside a neutron star to rapidly become inhomogeneous once the star's mass increases above some critical value. For a star whose mass is below the threshold, the field is instead nearly u… more

Date: November 4, 2003

Creator: Whinnett, A & Torres, D F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A New Paradigm for Identification of Classes of High Energy Gamma-Ray Sources

A large fraction of the expected number of source detections of the forthcoming observatory Gamma-ray Large Area Space Telescope (GLAST) will be initially unidentified. We argue that traditional methodological approaches to identify individual detections and/or populations of gamma-ray sources present procedural limitations. These limitations will hamper our ability to classify the populations lying in the anticipated dataset with the required degree of confidence, in particular for those for w… more

Date: April 8, 2005

Creator: Torres, D F & Reimer, O

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High energy (gamma)-ray emission from the starburst nucleus of NGC 253

The high density medium that characterizes the central regions of starburst galaxies and its power to accelerate particles up to relativistic energies make these objects good candidates as {gamma}-rays sources. In this paper, a self-consistent model of the multifrequency emission of the starburst galaxy NGC 253, from radio to gamma-rays, is presented. The model is in agreement with all current measurements and provides predictions for the high energy behavior of the NGC 253 central region. Pros… more

Date: June 15, 2005

Creator: Domingo-Santamaria, E. & Torres, D. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Generalizing the Thermodynamics State Relationships in KIVA-3V

The Peng-Robinson equation of state has been implemented into the KIVA-3V code to better handle high-pressure conditions typical of Diesel engine environments. The implementations modify pressure-volume-temperature relationships, specific heats, and departures in internal energy, among other thermodynamic partial derivatives. Computations show that significant deviations do occur for progressively heavier hydrocarbons. However, when these hydrocarbons exist in a mixture with a non-negligible po… more

Date: October 1, 2002

Creator: Trujillo, M.F.; O'Rourke, P. & Torres, D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST

For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10{sup o} from the Galactic plane, these clouds have typical distances of {approx}150 pc, angular sizes of {approx}1{sup o}, and masses of order tens of solar masses. These objects are passive sources of high-energy {gamma}-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-lat… more

Date: January 5, 2005

Creator: Torres, D F; Dame, T M & Digel, S W

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

ULXs, Microblazars, and the Unidentified EGERT Sources

We suggest that ultraluminous X-ray sources (ULXs) and some of the variable low latitude EGRET gamma-ray sources may be two different manifestations of the same underlying phenomena: high-mass microquasars with relativistic jets forming a small angle with the line of sight (i.e. microblazars). Microblazars with jets formed by relatively cool plasma (Lorentz factors for the leptons up to a few hundreds) naturally lead to ULXs. If the jet contains very energetic particles (high-energy cutoff abov… more

Date: May 1, 2003

Creator: Butt, Y M; Romero, G E & Torres, D F

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1

We show that changes in the orientation of the inner accretion disk of Cygnus X-1 affect the shape of the broad Fe K{alpha} emission line emitted from this object, in such a way that eV-level spectral resolution observations (such as those that will be carried out by the ASTRO-E2 satellite) can be used to analyze the dynamics of the disk. We here present a new diagnosis tool, supported by numerical simulations, by which short observations of Cygnus X-1, separated in time, can determine whether … more

Date: January 5, 2005

Creator: Torres, D F; Romero, G E; Barcons, X & Lu, Y

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Probing the precession of the inner accretion disk in Cygnus X-1

No Description Available.

Date: March 3, 2005

Creator: Torres, D F; Romero, G E; Barcons, X & Lu, Y

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Multicomponent fuel vaporization at high pressures.

We extend our multicomponent fuel model to high pressures using a Peng-Robinson equation of state, and implement the model into KIVA-3V. Phase equilibrium is achieved by equating liquid and vapor fugacities. The latent heat of vaporization and fuel enthalpies are also corrected for at high pressures. Numerical simulations of multicomponent evaporation are performed for single droplets for a diesel fuel surrogate at different pressures.

Date: January 1, 2002

Creator: Torres, D. J. (David J.) & O'Rourke, P. J. (Peter J.)

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Luminous Infrared Galaxies as Plausible y-ray Sources for GLAST and IACTs

We argue that luminous infrared galaxies (LIGs) may constitute a newly detectable population of {gamma}-ray sources for the next generation of ground and space-based high energy telescopes. Additionally, we report for the first time upper limits on their fluxes using data obtained with the EGRET telescope.

Date: July 8, 2004

Creator: Torres, D. F.; Reimer, O.; Domingo-Santamaria, E. & Digel, S. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Recovery of the orbital parameters and pulse evolution of V0332+53 during a huge outburst

The high mass X-ray binary (HMXB) V0332+53 became active at the end of 2004, with the outburst being monitored by RXTE and INTEGRAL at hard X-rays. Here, the orbital parameters are measured with the hard X-ray data through the fitting of the Doppler-shifted spin periods. The derived orbital period and the eccentricity are consistent with those reported by Stella et al. (1985) from earlier EXOSAT observations, whereas the projected semimajor axis and the periastron longitude are found to differ,… more

Date: May 5, 2005

Creator: Zhang, S.; Qu, J. L.; Song, L. M. & Torres, D. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs

Dust grains control the chemistry and cooling, and thus the gravitational collapse of interstellar clouds. Energetic particles, shocks and ionizing radiation can have a profound influence on the structure, lifetime and chemical reactivity of the dust, and therefore on the star formation efficiency. This would be especially important in forming galaxies, which exhibit powerful starburst (supernovae) and AGN (active galactic nucleus) activity. How dust properties are affected in such environments… more

Date: January 5, 2005

Creator: van Breugel, W; Bajt, S; Bradley, J; Bringa, E; Dai, Z; Felter, T et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough flu… more

Date: March 28, 2007

Creator: Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Energetic feedback in galaxies: Processing of interstellar silicate grains by cosmic rays

The formation and evolution of stars and galaxies is a complex process that involves the cooling and collapse of dense interstellar clouds as well as energetic feedback on these clouds. Interstellar dust grains are central to the radiative transfer, thermal balance, and molecular processes in these clouds and can provide an important diagnostic. Hence, the effects of energetic processing of interstellar dust may have significant consequences. r This may be studied in our own Galaxy, where obser… more

Date: May 10, 2006

Creator: Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G W M; Dai, Z R et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High Voltage Application of Explosively Formed Fuses

At Los Alamos, the authors have primarily applied Explosively Formed Fuse (EFF) techniques to high current systems. In these systems, the EFF has interrupted currents from 19 to 25 MA, thus diverting the current to low inductance loads. The magnitude of transferred current is determined by the ratio of storage inductance to load inductance, and with dynamic loads, the current has ranged from 12 to 20 MA. In a system with 18 MJ stored energy, the switch operates at a power up to 6 TW. The author… more

Date: October 18, 1998

Creator: Tasker, D. G.; Goforth, J. H.; Fowler, C. M.; Lopez, E. M.; Oona, H.; Marsh, S. P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Optimizing the Ranchero Coaxial Flux Compression Generator

Ranchero is an explosively driven magnetic flux-compression generator that has been developed, over the last four years, as a versatile power source for high energy density physics experiments. It is coaxial, and comprises a 15 cm-diameter armature and a 30-cm stator, each aluminum. The length may be varied to suit the demands of each experiment; thus far, lengths of 0.43 m and 1.4 m have been used. The stator is filled and driven by a high performance cast explosive, and the ultimate performan… more

Date: October 18, 1998

Creator: Tasker, D. G.; Goforth, J. H.; Fowler, C. M.; Lopez, E. A.; Oona, H.; King, J. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Hydrodynamic Liner Experiments Using the Ranchero Flux Compression Generator System

The authors have developed a system for driving hydrodynamic liners at currents approaching 30 MA. Their 43 cm module will deliver currents of interest, and when fully developed, the 1.4 m module will allow similar currents with more total system inductance. With these systems they can perform interesting physics experiments and support the Atlas development effort.

Date: October 18, 1998

Creator: Goforth, J. H.; Atchison, W. L.; Fowler, C. M.; Lopez, E. A.; Oona, H.; Tasker, D. G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ranchero Explosive Pulsed Power Experiments

The authors are developing the Ranchero high explosive pulsed power (HEPP) system to power cylindrically imploding solid-density liners for hydrodynamics experiments. The near-term goal is to conduct experiments in the regime pertinent to the Atlas Capacitor bank. That is, they will attempt to implode liners of {approximately}50 g mass at velocities approaching 15 km/sec. The basic building block of the HEPP system is a coaxial generator with a 304.8 mm diameter stator, and an initial armature … more

Date: June 27, 1999

Creator: Goforth, J. H.; Atchison, W. L.; Deninger, W. J.; Fowler, C. M.; Herrera, D. H.; King, J. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fermi Large Area Telescope View of the Core of the Radio Galaxy Centaurus A

Abstract Not Provided

Date: June 20, 2013

Creator: Naval Research Laboratory (U.S.). Space Science Division.

Item Type: Article

Partner: UNT Libraries Government Documents Department