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INTEGRAL U.S. Guest Observer Facility

NASA Funded INTEGRAL AO-3 Theory & Archive Investigator Abstracts

Proposal ID Name Proposal Short Title Abstract
003 COLLEEN WILSON STUDY OF EXO 2030+375 GLOBAL SPIN-UP AND OUTBURST STRUCTURE We propose to analyze archival INTEGRAL observations of EXO 2030+375 to measure the spin-frequency, examine the outburst structure, and search for evidence of apastron emission. Recently EXO 2030+375 transitioned from global spin-down to spin-up accompanied by brightening of the outbursts. Using INTEGRAL data, we will examine the recently proposed hypothesis that a pattern of spin frequency variations observed with BATSE is repeating with an 11-year cycle. We will compare energy spectra from RXTE and INTEGRAL to learn the mechanism producing EXO 2030+375's outburst structure consisting of an initital spike followed by a broad peak. We will use INTEGRAL archival data to measure or constrain apastron emission from EXO 2030+375 previously seen with non-imaging instruments.
004 MARKUS BOETTCHER BROADBAND SPECTRA AND SPECTRAL VARIABILITY OF MICROQUASAR JETS We propose to investigate the time-dependent broadband (radio through soft gamma-ray) emission produced in the jets of Galactic microquasars. We have developed semi-analytical solutions and numerical tools to solve the time-dependent electron kinematics and radiation transfer in the mildly relativistic jets of microquasars. Using those tools, we propose to develop diagnostics of various plausible source variability scenarios, in particular focusing on possible X-ray spectral hysteresis and soft gamma-ray emission and its variability. We propose further to re-analyze archival INTEGRAL observations of Galactic microquasars for comparison with our predictions.
010 RICHARD ROTHSCHILD BLACK HOLE CONTINUUM POWER SPECTRA & JET FORMATION We propose a program to use power spectra (PSDs) of archival INTEGRAL-ISGRI event data of bright black hole X-ray binaries to expand the rather limited knowledge about the rapid variability of these sources above 20 keV. This is of special interest for developing a consistent model of black hole accretion because of the association of the rapid variability with the hard spectral component, i.e., with the corona, the jet, or both. While ISGRI event data are already successfully validated against RXTE in terms of their absolute timing accuracy, as necessary, e.g., for period determinations, in the case of black hole binaries, the PSD continuum, i.e., the overall distribution of the source variability over a broad range of frequencies is relevant. This type of analysis requires a careful evaluation of the shape of the power spectra which is part of the proposed program. The main steps of this work are the following: (i) Further evaluation of ISGRI PSDs of the bright black hole binary Cyg X-1 by comparing to contemporary RXTE (PCA and HEXTE) data. Work on this has started. (ii) Development and testing of correction methods for ISGRI events and PSDs (background, dead-time, bad pixels). (iii) Automation of the data extraction up to corrected ISGRI PSDs. (iv) Systematic application to archival data of bright black hole binaries (e.g., Cyg X-1, GRS 1915+105, GX 339-4) and chi^2 modeling of the PSDs. (v) Correlation of the results with parameters from jet model fits to RXTE and INTEGRAL spectra (the spectral fitting itself being a separate project which has already started). For Cyg X-1 radio monitoring data can also be included in the fits and correlations.
033 DEMOSTHENES KAZANAS MODELING THE INTEGRAL GRB SPECTRA BY "NUCLEAR PILE" MODEL The isotropy of Gamma Ray Bursts (GRB) implies that a number of them will necessarily occur within the INTEGRAL field of view, and indeed roughly a dozen have so far done so. Because of their intrinsically high fluxes and the fact that their energy of peak emission $E_p$ is in the 100 keV - few MeV range are ideally suited for study by INTEGRAL. We have recently put forward a model that accounts for the observed range of GRB peak emission in a well defined, largely parameter free fashion. We propose to model GRB properties within the framework of this model in the spectral and time domain and compare them to the INTEGRAL results. Particular emphasis will be placed on the correlations between the peak luminosity and $E_p$ as well as their possible time evolution.
039 SANDEEP PATEL PHASE RESOLVED X-RAY SPECTROSCOPY OF ACCRETING PULSARS The large amount of INTEGRAL galactic survey observations have provided data that is ideal for studying accreting binary systems. Particularly of interest is the newly discovered class of highly absorbed pulsating NS. Currently the available software (OSA 4.2) is not able to properly extract phase resolved spectra of these sources. We propose to develop new tools to perform phase resolved spectroscopy and exploit these tools to study physical processes in accreting pulsars emitting in the X-ray/soft gamma-ray range. We will test the tools using data from the persistant pulsars Vela X-1 and GX 301-2, and the transient V 0332+53. We will then extend our study to 2 newly discovered transient sources for which pulsations have been discovered, IGR J16358-4726 and IGR 16320-4751.
040 MATTHEW BARING MODELING THE HARD X-RAY COMPONENTS OF ANOMALOUS X-RAY PULSARS A significant new development in the study of Anomalous X-ray Pulsars (AXPs) has been the recent discovery by INTEGRAL, with supporting archival data from RXTE, of flat, hard X-ray components in three AXPs. These non-thermal spectral components differ dramatically from the steeper quasi-power-law tails seen in the classic X-ray band in these sources. A prime candidate mechanism for generating this new component is resonant (magnetic) Compton upscattering. This process is very efficient in the strong magnetic fields present in AXPs. We propose here to develop an inner magnetospheric model for upscattering of surface thermal X-rays in AXPs, to explore whether such resonant upscattering can explain the 10-50 keV spectra seen by INTEGRAL, and to make predictions concerning the pulse profiles and polarization at different energies. Non-thermal electrons will be injected, and their rapid cooling due to the resonant scattering will be tracked. A suite of observational diagnostics on model geometry will be generated. Both kinetic equation and Monte Carlo simulation techniques will be used, the former to facilitate exploration of global properties of upscattering and cooling on small spatial scales, and the latter to provide a comprehensive model of radiation and electron propagation and interaction in a full magnetospheric geometry.
044 MARK LEISING COMBINED ANALYSIS OF INTEGRAL/SPI AND CGRO/OSSE POSITRON ANNIHILATION DATA The origin of the bright galactic positron annihilation line and continuum emission remains a mystery despite more than three decades of study, and will not be easily clarified soon. We propose to study jointly the electron-positron annihilation radiation from archival data from the INTEGRAL SPI and Compton Observatory OSSE instruments, as well as other satellite missions. There is good reason to believe that a combined analysis of these complementary data sets will yield more information than a simple average of separate analyses. This is true of both spatial (mapping) studies and spectral (line shape and line-to-continuum ratio) studies. We expect to derive better constraints on the spatial distribution, total flux, and the characteristics of the annihilation medium than are available from SPI data alone.
046 KEN-ICHI NISHIKAWA PARTICLE ACCELERATION AND EMISSION FROM SUPERNOVA REMNANTS We propose to apply numerical simulations and modeling to the particle acceleration, magnetic field generation, and emission from shocks required by the observed X-ray emission from supernova remnants. In particular, the project involves the study of collisionless shocks associated with supernova remnants observed by INTEGRAL. In collisionless shocks, plasma waves and their associated instabilities (e.g., the Weibel, Buneman and other two-stream instabilities) are responsible for particle (electron, positron, and ion) acceleration and magnetic field generation. A 3-D relativistic electromagnetic particle (REMP) code will be used to investigate the shock processes in magnetized electron-ion and electron-positron plasmas. The evolution of two-stream instabilities will be examined in a realistic way by simulating the collision between outflow and ambient plasmas. Thus, we can study shock formation in addition to the microscopic shock processes. In our investigations, the density of the plasmas, the ambient magnetic field strength and direction, and Lorentz factor will be varied in order to evaluate the effect of changes in X-ray emission in remnants. Systematic theoretical/simulation studies of the plasma dynamics, associated particle acceleration, magnetic field generation and radiation and comparison with observations will enable us to address the state of the plasma associated with the X-ray emission and its variability in supernova remnants.

Last updated:Thursday, 22-Sep-2005 14:06:54 EDT .