Technology and Economics, Inc. Technology Application Team

Technology + Economics, Inc. (T+E), under contract to the NASA Headquarters Technology Transfer Division, operates a Technology Applications Team (TATeam) to assist in the transfer of NASA-developed aerospace technology. T+E's specific areas of interest are selected urban needs at the local, county, and state levels. T+E contacts users and user agencies at the local, state, and county levels to assist in identifying significant urban needs amenable to potential applications of aerospace technology. Once viable urban needs have been identified in this manner, or through independent research, T+E searches the NASA technology database for technology and/or expertise applicable to the problem. Activities currently under way concerning potential aerospace applications are discussed

Off-Axis Afterglow Light Curves from High-Resolution Hydrodynamical Jet Simulations

Numerical jet simulations serve a valuable role in calculating gamma-ray burst afterglow emission beyond analytical approximations. Here we present the results of high resolution 2D simulations of decelerating relativistic jets performed using the RAM adaptive mesh refinement relativistic hydrodynamics code. We have applied a separate synchrotron radiation code to the simulation results in order to calculate light curves at frequencies varying from radio to X-ray for observers at various angles from the jet axis. We provide a confirmation from radio light curves from simulations rather than from a simplified jet model for earlier results in the literature finding that only a very small number of local Ibc supernovae can possibly harbor an orphan afterglow. Also, recent studies have noted an unexpected lack of observed jet breaks in the Swift sample. Using a jet simulation with physical parameters representative for an average Swift sample burst, such as a jet half opening angle of 0.1 rad and a source redshift of z = 2.23, we have created synthetic light curves at 1.5 keV with artificial errors while accounting for Swift instrument biases as well. A large set of these light curves have been generated and analyzed using a Monte Carlo approach. Single and broken power law fits are compared. We find that for increasing observer angle, the jet break quickly becomes hard to detect. This holds true even when the observer remains well within the jet opening angle. We find that the odds that a Swift light curve from a randomly oriented 0.1 radians jet at z = 2.23 will exhibit a jet break at the 3 sigma level are only 12 percent. The observer angle therefore provides a natural explanation for the lack of perceived jet breaks in the Swift sample.Comment: 4 pages, 3 figures. First of two contributions to proceedings GRB2010 Maryland conference. Editors: McEnery, Racusin and Gehrels. The data from this paper is publicly available from http://cosmo.nyu.edu/afterglowlibrary

An on-line library of afterglow light curves

Numerical studies of gamma-ray burst afterglow jets reveal significant qualitative differences with simplified analytical models. We present an on-line library of synthetic afterglow light curves and broadband spectra for use in interpreting observational data. Light curves have been calculated for various physics settings such as explosion energy and circumburst structure, as well as differing jet parameters and observer angle and redshift. Calculations gave been done for observer frequencies ranging from low radio to X-ray and for observer times from hours to decades after the burst. The light curves have been calculated from high-resolution 2D hydrodynamical simulations performed with the RAM adaptive-mesh refinement code and a detailed synchrotron radiation code. The library will contain both generic afterglow simulations as well as specific case studies and will be freely accessible at http://cosmo.nyu.edu/afterglowlibrary . The synthetic light curves can be used as a check on the accuracy of physical parameters derived from analytical model fits to afterglow data, to quantitatively explore the consequences of varying parameters such as observer angle and for accurate predictions of future telescope data.Comment: 4 pages, 2 figures. Second of two contributions to proceedings GRB2010 Maryland conference. Editors: McEnery, Racusin and Gehrels. The data from this paper is publicly available from http://cosmo.nyu.edu/afterglowlibrary

MHD simulations of the collapsar model for GRBs

We present results from axisymmetric, time-dependent magnetohydrodynamic (MHD) simulations of the collapsar model for gamma-ray bursts. Our main conclusion is that, within the collapsar model, MHD effects alone are able to launch, accelerate and sustain a strong polar outflow. We also find that the outflow is Poynting flux-dominated, and note that this provides favorable initial conditions for the subsequent production of a baryon-poor fireball.Comment: 4 pages, to appear in proceedings of "2003 GRB Conference" (Santa Fe, NM, September 8-12, 2003), needs aipprocs LaTeX class, movies are available at http://rocinante.colorado.edu/~proga

Cosmic rays from trans-relativistic supernovae

We derive constraints that must be satisfied by the sources of ~10^{15} to ~10^{18} eV cosmic rays, under the assumption that the sources are Galactic. We show that while these constraints are not satisfied by ordinary supernovae (SNe), which are believed to be the sources of <10^{15} eV cosmic rays, they may be satisfied by the recently discovered class of trans-relativistic supernovae (TRSNe), which were observed in association with gamma-ray bursts. We define TRSNe as SNe that deposit a large fraction, f_R>10^{-2}, of their kinetic energy in mildly relativistic, \gamma\beta>1, ejecta. The high velocity ejecta enable particle acceleration to ~10^{18} eV, and the large value of f_R (compared to f_R~10^{-7} for ordinary SNe) ensures that if TRSNe produce the observed ~10^{18} eV cosmic ray flux, they do not overproduce the flux at lower energies. This, combined with the estimated rate and energy production of TRSNe, imply that Galactic TRSNe may be the sources of cosmic rays with energies up to ~10^{18}eV .Comment: Accepted to ApJ. Expanded abstract, introduction, discussio