Part II. Posters



Title: A Model for the Spatial Distribution of Relativistic Electrons in the Crab Nebula
Author: E. Amato
Affil: Dept. of Astronomy and Space Science, University of Florence, Largo E. Fermi 5, I-50125, Firenze, Italy
Abstract: A model for the spatial distribution of relativistic electrons in the Crab Nebula is proposed. Particles injected in the vicinity of the pulsar propagate in a magnetic field of time-dependent but spatially constant intensity. A good description of the nebular synchrotron emission, from radio to X-ray frequencies, is obtained if particle diffusion with respect to the azimuthal field lines is taken into account.


Title: General-Relativistic MHD Simulation of Jets from a Geometrically Thin Accretion Disk Around a Schwarzschild Black Hole
Authors: S. I. Aoki(1), S. Koide(2), K. Shibata(3), and T. Kudoh(4)
Affil: (1) Department of Astronomy, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan (2) Faculty of Engineering, Toyama University, Gofuku, Toyama 930, Japan (3) Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan (4) Solar Physics Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan
Abstract: We have performed a 2.5D, nonsteady, general-relativistic MHD simulation. Initially, we assumed a uniform magnetic field, a geometrically thin accretion disk rotating at Keplerian velocity, and a hydrostatic corona around a Schwarzschild black hole. We have investigated the formation mechanism of gas-pressure driven jets expected by Koide et al. and found the strong dependence of jet velocities (gamma_j = 1 / sqrt[1 - V_j^2]; Lorentz factor of jets) on the ratio of the density of the accretion disk to that of the corona (rho_d / rho_c), where gamma_j^2 - gamma_j ~ (rho_d / rho_c)^[0.75].


Title: Electron Trapping and Precipitation in Asymmetric Solar Flare Loops
Authors: M. J. Aschwanden(1), L. Fletcher(1), T. Sakao(2), T. Kosugi(3), and H. Hudson(4)
Affil: (1) Lockheed Martin Advanced Technology Center, Solar and Astrophysics Lab., Dept. L9-41, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304, U.S.A. (2) Natl. Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8599, Japan (3) Inst. Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan (4) Solar Physics Research Corporation, 4720 Calle Desecada, Tucson, AZ 85718, U.S.A.
Abstract: Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields.


Title: Active Late-Type Stellar Coronae: Hints for Flare Heating?
Authors: M. Audard(1), M. Gudel(1), J. J. Drake(2), V. Kashyap(2), and E. F. Guinan(3)
Affil: (1) Paul Scherrer Institute, 5232 Villigen PSI, Switzerland (2) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, U.S.A. (3) Dept. of Astronomy & Astrophysics, Villanova University, Villanova, PA 19085, U.S.A.
Abstract: The Extreme Ultraviolet Explorer data archive has been used to study flare energy distributions and infer the role of flares in coronal heating. We have constructed flare number distributions as a function of observed EUV and X-ray emitted thermal energy. We find cumulative flare distributions of the form N(>E) ~ E^[-alpha + 1] with alpha ~ 1.5--2.6. We present results in the context of spectral type classification.


Title: Stochastic Acceleration and Nonthermal Radiation in Clusters of Galaxies
Authors: P. Blasi and A. Olinto
Affil: Department of Astronomy & Astrophysics, The University of Chicago and E. Fermi Institute, 5640 S. Ellis Av., Chicago, IL 60637, U.S.A.
Abstract: We study the possibility that the recently detected hard X-ray excess from some clusters of galaxies is due to bremsstrahlung emission of a nonthermal tail in the electron distribution produced by stochastic acceleration in a background of MHD waves. We find that this scenario requires an overall level of fluctuations which is only "delta B"^2 / B^2 ~ 3% for a magnetic field B on the order of microgauss. Despite the reasonable values for these parameters, a large rate of injection of waves is needed to compensate the damping of the waves.


Title: Relativistic Adiabatic Shocks in Accretion Flows
Authors: D. M. Caditz and S. Tsuruta
Affil: Department of Physics, Montana State University, Bozeman, MT 59717, U.S.A.
Abstract: Accretion flows onto compact astronomical sources are likely to be supersonic, and shock waves may therefore be common in such flows. Plasma passing through a shock front will be compressed and heated according to the jump conditions across the shock discontinuity. Shocks in accretion flows may therefore have important consequences for the flow structure and emission characteristics. The equations governing adiabatic (nonradiative) shocks in relativistic plasmas are presented including the effects of radiation pressure and energy density, and pair equilibria in the postshock flow. We find that postshock states for accretion flows within cool, optically thick, accretion-driven sources such as AGN become radiation- or pair-dominated, and the postshock plasma will likely become optically thin before returning to steady-state conditions.


Title: Pulsar Geometrodynamics: Relativistic Radiative Plasma Theory and its Associated Quantum Phenomena
Author: A. A. da Costa
Affil: Centro de Electrodinamica, Instituto Superior Tecnico, 1049-001, Lisboa, Portugal
Abstract: Plasma motion in pulsar magnetospheres is quasi-classical due to curvature radiation of highly energetic gamma-ray photons, implying an extension to the kinetic theory of plasmas. But with high energies involved, other quantum radiative processes become important in the context of vacuum (quantum) electrodynamics.


Title: X-ray Emission from Supermassive Black Holes in Elliptical Galaxies and Low Radiative-efficiency Accretion
Authors: T. Di Matteo(1) and S. W. Allen(2)
Affil: (1) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, U.S.A. (2) Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, U.K.
Abstract: We discuss the detection of hard, power-law emission components in the X-ray spectra of six nearby, giant elliptical galaxies observed with the ASCA satellite and its implication for low-radiative efficiency accretion models around the central, supermassive black holes.


Title: Magnetic Helicity, Dynamo Action, Reconnection, and Particle Acceleration
Authors: G. B. Field(1) and E. G. Blackman(2)
Affil: (1) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, U.S.A. (2) California Institute of Technology, Pasadena, CA 91125, U.S.A.
Abstract: Blackman & Field have shown that a working "alpha-omega" dynamo requires finite but opposite flows of small- and large-scale magnetic helicity through a body's surface. The helicity is accompanied by magnetic energy available for dissipation. The observed solar coronal nonthermal power is consistent with the derived lower limit required. This link between dynamo field generation and nonthermal emission should generally apply to stars, spiral galaxies, and accretion disks.


Title: Starquakes in Neutron Stars
Authors: L. M. Franco(1), B. Link(2), and R. I. Epstein(3)
Affil: (1) University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, U.S.A. (2) Montana State Univ., Dept. of Physics, Bozeman, MT 59717, U.S.A. (3) Los Alamos National Lab, MS D436, Los Alamos, NM 87545, U.S.A.
Abstract: The Crab and other pulsars suffer sudden and permanent increases in their spin-down rates in association with glitches, suggesting that the external torque on these objects grows in steps. Here, we describe how torque changes may arise from starquakes, occurring as the star spins down and its rigid crust becomes less oblate. We study the evolution of strain in the crust, the initiation of starquakes, the effects on the magnetic field geometry, and possible observable consequences for neutron star spin down. We find that the stellar crust begins breaking at the rotational equator, forming a fault inclined at an angle to the equator and directed toward the magnetic poles. The resulting asymmetric matter redistribution produces a misalignment of the angular momentum and spin axes. Subsequently, damped precession to a new rotational state increases the angle between rotation and magnetic axes. The change in this angle could increase the external torque, producing a permanent increase in the spin-down rate.


Title: Gyrosynchrotron Emission from Stellar Coronae
Authors: M. Gudel(1) and A. Zucker(2)
Affil: (1) Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland (2) Institute of Astronomy, ETH Zentrum, CH-8092 Zurich, Switzerland
Abstract: We analyze quiescent radio spectra of main-sequence cool stars in terms of a simple gyrosynchrotron model. We find that the underlying (assumed) power-law electron distribution is often very hard, with power-law indices (in dN / dE ~ E^[-delta]) mostly around delta ~ 2--3.5.


Title: X-ray Radiation from Flare-heated Coronal Plasma
Author: M. Gudel
Affil: Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
Abstract: We investigate the reaction of a coronal loop in the case of repetitive flares, with a power-law distribution in energy, injected into a rigid magnetic loop. Emission measure distributions and temperature-dependent modulations of the radiation are briefly discussed.


Title: Primordial Flares, Flux Tubes, and Gamma-ray Bursts
Author: K. M. Hiremath
Affil: Indian Institute of Astrophysics, Bangalore-560034, India
Abstract: Given the prevailing physical conditions in the cosmic environment, the similarity of solar transients and cosmic gamma-ray bursts suggests that the most promising energy source for the latter may be primordial flares, which derive energy from magnetic reconnection.


Title: Internal Rotation of AB Doradus
Author: K. M. Hiremath
Affil: Indian Institute of Astrophysics, Bangalore-560034, India
Abstract: Using Chandrasekhar's MHD equations, we solve for the steady part of the internal rotation of AB Doradus. We estimate the size of the convective envelope to be ~40% of the radius and the rotation velocity at the base to be not less than 1.42x10^[-4] rad/sec. This study also yields the steady part of the toroidal magnetic field which is distributed throughout the convective envelope. We present rotational and toroidal magnetic field profiles in the interior and conjecture on the time-dependent part of the magnetic field.


Title: Which Forces Accelerate Jets?
Authors: S. X. Kato(1), T. Kudoh(2), and K. Shibata(3)
Affil: (1) Department of Astronomy, University of Tokyo, Japan (2) National Astronomical Observatory, Japan (3) Kwasan Observatory, Kyoto University, Japan
Abstract: We performed 2.5-dimensional, nonsteady MHD simulations of jets from geometrically thin accretion disks and investigated the acceleration forces of jets in detail.


Title: Particle Acceleration and Radiation in Magnetospheres of Collapsing Stars
Author: V. Kryvdyk
Affil: Department of Astronomy, Kiev University, Glushkova 6, UKR-252022, Kiev, Ukraine
Abstract: Particle dynamics and nonthermal emission therefrom in the magnetospheres of collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of charged particles (power-law, relativistic Maxwell, and Boltzmann distributions) are considered . The radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and an initial power-law particle energy distribution in the magnetosphere. The effects can be observed by means of modern instruments.


Title: Collimation of Magnetically Driven Outflows from Accretion Disks
Authors: T. Kudoh(1), R. Matsumoto(2), and K. Shibata(3)
Affil: (1) Solar Physics Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan (2) Department of Physics, Faculty of Science, Chiba University, Inageku, Chiba 263-8522, Japan (3) Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto 607-8471, Japan
Abstract: We performed 2.5-dimensional, nonsteady MHD numerical simulations to investigate the acceleration and collimation of magnetically driven outflows from accretion disks, including the accretion process itself, consistently. As an initial condition, we used a paraboloidal magnetic field line that is produced by electric current on the equatorial plane. We found that the outflow ejected from the accretion disk is collimated by the pinch effect of the toroidal component of the magnetic field that is produced by the rotation of the disk.


Title: A Scaling Law for Magnetic Flux Tubes on an AGN Accretion Disk
Authors: A. M. K. LeRoux, D. W. Longcope, and S. Tsuruta
Affil: Physics Department, Montana State University, Bozeman, MT 59717, U.S.A.
Abstract: An ASCA observation of Seyfert galaxy NGC 3227 showed flares with a linear increase and exponential decrease similar to that of solar flares. We derive a scaling law relating the loop length of a magnetic flux tube to rise and decay times of the flare using cooling mechanisms suitable for the central engine of a Seyfert galaxy. The predicted loop lengths are consistent with physical constraints on the plasma dynamics, suggesting that the same mechanism which explains solar flares may explain variability in Seyfert galaxies.


Title: Hidden Blazars In Radio Loud Quasars?
Author: F. Ma
Affil: The University of Texas at Austin, Austin, TX 78712, U.S.A.
Abstract: We present the initial results from our search for hidden blazars via Civ emission line variability among radio loud quasars. The implications on models of quasar Broad Emission Line Regions are discussed, and we focus on the tidally disrupted star model.


Title: Hard X-ray Spectrum of the Above-the-Looptop Source in Impulsive Solar Flares
Author: S. Masuda
Affil: Solar-Terrestrial Environment Laboratory, Nagoya University, Toyokawa, Aichi 442-8507, Japan
Abstract: N/A


Title: Numerical Simulations of the Precessing Jets of SS433
Authors: E. Muller and W. Brinkmann
Affil: MPI fur Astrophysik, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany
Abstract: The unique Galactic object SS433 contains the best-studied relativistic jets, and their physical parameters (velocity, temperature, density) are known to an astronomically unprecedented accuracy, i.e., to factors of order unity. The comparison of numerical simulations of these jets with observations provides deeper insight into the SS433/W50 system and is ideal for testing our understanding of the jet phenomenon in general.


Title: Statistical Properties of Kerr BH Flywheel Model of QSOs/AGNs
Author: S. Nitta
Affil: National Astronomical Observatory Japan, 2-21-1 Osawa, Mitaka, 181-8588 Japan
Abstract: The aim of this work is to demonstrate the properties of the magnetospheric model around Kerr black holes, so-called the ``fly-wheel'' (rotation powered) model. The fly-wheel engine of the BH accretion disk system is applied to the statistics of QSOs/AGNs. Nitta, Takahashi, & Tomimatsu clarified the individual evolution of the Kerr black-hole fly-wheel engine, which is parameterized by black-hole mass, initial Kerr parameter, magnetic field near the horizon, and a dimensionless small parameter. We impose a statistical model for the initial mass function of an ensemble of black holes using the Press-Schechter formalism. With the help of additional assumptions, we can discuss the evolution of the luminosity function and the spatial number density (population) of QSOs/AGNs. The result explains well the decrease of very bright QSOs and decrease of population after z ~ 2.


Title: Interaction of the SS433 Jet with the Interstellar Medium
Authors: P. O'Neill(1), R. Sood(1), P. Durouchoux(2), and S. Safi-Harb(3)
Affil: (1) School of Physics, University College, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia (2) CE Saclay, DSM, DAPNIA, Service d'Astrophysique, Cedex, France (3) NASA, GSFC, Code 662, Greenbelt, MD 20771, U.S.A.
Abstract: X-ray emission observed from the SS433/W50 system has been interpreted as resulting from the interaction of the binary jets with the surrounding medium. We have been carrying out millimetre wavelength measurements of this system. We find no evidence for the association of a molecular cloud with the eastern jet, but we do find evidence for a strong association with the western jet.


Title: High-energy Radiation from a Model of Quasars, AGNs, and the Galactic Center with Magnetic Monopoles
Author: Q.-H. Peng
Affil: Department of Astronomy, Nanjing University, Nanjing, 210093, China
Abstract: The structural parameters of the supermassive object at the Galactic Center and its high-energy radiation are estimated according to observations in near-infrared radiation, under the model of a supermassive object with magnetic monopoles.


Title: NLTE Model Atmospheres for Extremely Hot Compact Stars
Authors: T. Rauch, J. L. Deetjen, S. Dreizler, and K. Werner
Affil: Institut fur Astronomie und Astrophysik, Univ. Tubingen, Germany
Abstract: Present observational techniques provide stellar spectra with high resolution at a high signal-to-noise ratio over the complete wavelength range---from the far infrared to X-rays.

The effects of Non-``Local Thermal Equilibrium'' (NLTE) are particularly important for hot stars, hence the use of reliable NLTE stellar model atmosphere fluxes is required for an adequate spectral analysis.

State-of-the-art NLTE model atmospheres include metal-line blanketing of millions of lines of all elements from hydrogen up to the iron-group elements, and thus permit precise analyses of extremely hot compact stars, e.g., central stars of planetary nebulae, PG 1159 stars, white dwarfs, and neutron stars. Their careful spectroscopic study is of great interest in several branches of modern astrophysics, e.g., stellar and galactic evolution, and interstellar matter.


Title: Far-ultraviolet Emission from Supernova Remnant Shocks
Authors: R. Sankrit(1), W. P. Blair(1), and the FUSE SNR Team(2)
Affil: (1) Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, U.S.A. (2) JHU, Princeton, GSFC, IAP, UC Berkeley
Abstract: Supernova remnant shocks produce a rich spectrum of lines in the ultraviolet. Among these are important diagnostic resonance lines of Ovi, Ciii, and Niii which lie in the bandpass observable with the recently launched Far Ultraviolet Spectroscopic Explorer. We present an overview of a PI program to observe several supernova remnants using this new telescope.


Title: Self-organized Criticality with Data from MCG-6-30-15?
Authors: R. Sivron(1), E. Goralski(2), A. LeRoux(3), S. Tsuruta(3), and H. Kunieda(4)
Affil: (1) Bucknell University, Lewisburg, PA 17837, U.S.A. (2) GVSU, Allendale, MI 49404, U.S.A. (3) MSU, Bozeman, MT 59717, U.S.A. (4) Nagoya University, Nagoya, Japan
Abstract: We explain why compact sources are nonlinear and investigate the nonlinearity of MCG-6-30-15. We argue that the central engine of this Seyfert nucleus is compact and show that it exhibits a specific nonlinear behavior similar to that of a system in a critically self-organized state.


Title: Candidates for Optical Counterpart in the Field of PSR 1821-24 in M28
Author: F. K. Sutaria
Affil: Inter-University Centre for Astronomy and Astrophysics, Pune, India
Abstract: The 3-ms, X-ray pulsar RX J1824.2-2R52P has been identified at the 2-sigma level as a possible X-ray counterpart of the radio pulsar PSR 1821-24. The present work uses archival HST data for M28 to set upper limits on the optical V-band magnitude of PSR 1821-24 / RX J1824.2-2R452P. The optical limit extends the multiwavelength observations for this source and would provide constraints for theoretical models of pulsar emission.


Title: Magnetic Field Effects upon Neutron Star Cooling
Authors: M. A. Teter, D. Rilett, and S. Tsuruta
Affil: Department of Physics, Montana State University, Bozeman, MT 59717, U.S.A.
Abstract: The principal mechanism for neutron-star cooling during the early period of its thermal evolution is the emission of neutrinos. Because the neutrino luminosity is very large compared to the photon luminosity, most approximations leave any small effects upon the photon luminosity during the early part of the evolution as ignorable. However, for a field strength of H ~ 10^[12] gauss, taking those effects into consideration in terms of a decreased photon flux from the surface means that the energy not released from the surface as photons is still trapped within the star. Energy conservation requires that neutrino emission must make up for the difference, thereby modifying the onset of the photon era of cooling. A magnetic field of large magnitude will change the surface temperature. A proper treatment of the neutron-star cooling problem in a large magnetic field requires that tangential heat flow be taken into account. This presentation shows the preliminary results of a study that is leading toward a full two-dimensional calculation of the thermal evolution.


Title: The Isolated Neutron Star RX J185635-3754
Authors: F. M. Walter, P. An, J. Lattimer, and M. Prakash
Affil: Dept. of Physics and Astronomy, SUNY, Stony Brook, NY 11794-3800, U.S.A.
Abstract: We use optical and X-ray data to investigate the atmosphere of the isolated neutron star RX J185635-3754. The space motion suggests an origin about 2 million years ago in the Upper Cen-Lup OB association.


Title: Reacceleration of Relativistic Electrons by Turbulent Alfven Waves in Radio Jets
Authors: D.-Y. Wang and Y. Ma
Affil: Purple Mountain Observatory, Nanjing, 210008, China
Abstract: Relativistic electrons may be effectively accelerated by turbulent Alfven waves in radio jets. The acceleration spectrum is a power law with the electron energy as high as gamma ~ 10^6, but the spectrum index is ~1.2 in the condition of diffusion approximation, which is less than the observation value.


Title: Statistical Properties of Magnetic Separators in Model Active Regions
Authors: B. T. Welsch and D. W. Longcope
Affil: Department of Physics, Montana State University - Bozeman, Bozeman, MT 59717-3840, U.S.A.
Abstract: ``Transient brightenings'' (or ``microflares'') regularly deposit 10^[27] ergs of energy in the solar corona, and account for perhaps 20% of the active corona's power. We assume these events correspond to episodes of magnetic reconnection along {\it magnetic separators} in the solar corona. Using the techniques of magnetic charge topology, we model active region fields as arising from normally distributed collections of ``magnetic charges'', point-like sources/sinks of flux (or field lines). Here, we present statistically determined separator (X-ray loop) lengths, derived from first principles. We are in the process of statistical calculations of heating rates due to reconnection events along many separators.


Title: Numerical Simulations of Solar Flares
Authors: T. Yokoyama(1) and K. Shibata(2)
Affil: (1) National Astronomical Observatory of Japan, Japan (2) Kwasan Observatory, Kyoto University, Japan
Abstract: N/A


Title: Summary of Posters on Solar Physics
Author: M. J. Aschwanden
Affil: Lockheed Martin Advanced Technology Center, Solar and Astrophysics Lab., Dept.L9-41, Bldg.252, 3251 Hanover St., Palo Alto, CA 94304, U.S.A.
Abstract: N/A