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