High Energy Astrophysics Posters: Abstracts

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2101: Gravitationally Lensed Oscillations of a Slender Torus

Authors: Michal Bursa (Charles University Prague)

Using a 3D ray-tracing numerical code we study rapid variability of radiation originating from accreting compact objects. We construct a toy model of an oscillating torus in the slender approximation assuming thermal bremsstrahlung for the intrinsic emissivity of the medium and we compute observed (predicted) radiation signal including contribution of indirect (higher-order) images and caustics in the Schwarzschild spacetime. We show that the simplest oscillation mode in an accretion flow, axisymmetric up-and-down motion at the meridional epicyclic frequency, may be directly observable when it occurs in the inner parts of accretion flow around neutron stars and black holes. Together with the second oscillation mode, an in-and-out motion at the radial epicyclic frequency, it may then be responsible for the high-frequency modulations of the X-ray flux observed at two distinct frequencies (twin HF-QPOs) in microquasars and low-mass X-ray binaries.

2102: From Hydrodynamical Instability to Turbulent Viscosity in Accretion Disks

Authors: A.Fridman (Institute of Astronomy, Russian Academy of Sciences)

The majority instabilities proposed as a source of the turbulence of accretion disks have either a low level of nonlinear saturation or not sufficiently large wave length, corresponding to maximum growth rate, etc. This does not make possible to reach the necessary value of turbulent viscosity. An instability found in the 3D model of an accretion disk in close binary stars is prevented from the drawbacks mentioned above. This instability is exited by radial gradients of the surface density of the accretion disk. The instability causes a density wave containing a one-armed spiral and an anticyclonic vortex. The hydrodynamical instability results in a turbulence of the accretion disc. A value of turbulent viscosity coefficient is in accordance with both, the value of a numerical viscosity in presented calculations, and the results of observations. The period of the density wave rotation is in agreement with the typical periods of light curve variations observed in cataclysmic binary stars.

2103: Interaction Between a Dense Stellar Cluster and an Inactive Accretion Disc in a Galactic Core

Authors: V.Karas, L.Subr (Astronomical Institute)

We discuss the structure of a central stellar cluster whose dynamics is influenced by gravitation of a supermassive black hole and by the dissipative interaction of orbiting stars with an accretion disc. We also take the effect of disc self-gravity into account. We show that the cluster properties are determined predominantly by the radial profile of the disc surface density. We develop a simple steady-state model of the central cluster and we estimate the rate at which stars migrate to the centre.

2104: Polarization Signatures of Strong Gravity in Black-Hole Accretion Discs

Authors: V.Karas, M.Dovciak, J.Horak, G.Matt (Astronomical Institute)

We discuss effects of strong gravity on the polarization properties of a black-hole accretion disc. The intrinsic polarization is computed taking into account light scattered on the disc surface and using different approximations. The gravitational field of a black hole influences the Stokes parameters of reflected radiation propagating to a distant observer. The lamp-post model is explored as an example of a specific geometrical arrangement relevant for AGNs. The degree and the angle of polarization are computed as functions of the observer inclination angle, of the inner radius of the disc emitting region, and of other parameters of the model. The expected polarization should be detectable by new generation polarimeters, such as the one planned for the Xeus mission.

2105: Iron Fluorescent Line Emission From Black Hole Accretion Disks With Magnetic Reconnection-Heated Corona

Authors: Norita Kawanaka, Shin Mineshige(Yukawa Institute for Theoretical Physics)

We investigate the iron K-alpha fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. We adopt the corona model constructed by Liu et al. (2003) in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops. In hard spectrum state, the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced via thermal Comptonization, impinge the underlying disk, and drive iron line fluorescence. In this case, the local emmisivity of iron line on the disk is approximately proportional to r^(-5). The profile derived from this model can fit well the observational data of MCG-6-30-15 with the profile derived theoretically.

2106: Stability of C-Modes on Accretion Disks around Black Holes

Authors: Nicolás Figueroa-Hidalgo, Giovanni Sáenz-Arce, Abraham Madrigal-Ramírez (University of Costa Rica)

We compute numerically the sign and value of the viscosity-induced damping rate of fundamental c-, or corrugation, mode oscillations in the inner part of accretion disks around black holes. The damping of these oscillations has been studied analytically by Ortega–Rodriguez & Wagoner (2000). However, their work did not determine the sign of the damping rate for the c-modes. We start from their results and calculate the damping rate for different values of the black hole´s angular momentum. Stability considerations might be important as these (or similar) modes could explain certain QPOs (quasi-periodic oscillations) measured by the Rossi X-ray Timing Explorer (see, e.g., Strohmayer).

2107: Stochastic Proton and Electron Acceleration near Black Holes

Authors: Siming Liu, Vahe Petrosian (Stanford University)

In this paper we study the acceleration of protons and electrons by turbulent plasma waves generated via MRI or/and magnetic reconnections in hot accretion tori around black holes, ranging from stellar mass ones in X-ray binaries to supermassive black holes in AGNs. Energy loss processes dominated at different energy ranges and under different physical conditions are reviewed. Emphases are then put on the acceleration to relativistic energies of electrons and protons from a thermal background with a temperature close to the virial value, their radiative signatures, and their possible connections to the formation of relativistic outflows. We investigate the dependences of model predictions on the size of the acceleration site, which is proportional to the black hole mass, the gas density, which depends on the mass accretion rate, and the energy partitions between the magnetic field, the turbulence, and the thermal energy of the plasmas for a general spectrum of the turbulent plasma waves.

2108: Global Disk Oscillation Modes in Cataclysmic Variables

Authors: Manuel Ortega-Rodriguez (Universidad de Costa Rica)

Diskoseismology, the theoretical study of hydrodynamic global perturbations in geometrically thin, optically thick accretion disks around black holes, has been used in the past to allow one to compute the elusive angular momentum parameter of the black hole in terms of the perturbations’ oscillation period. The procedure consists of a normal mode analysis. The general formalism developed by diskoseismologists for relativistic systems can be readily applied to the Newtonian case of cataclysmic variables. Some of these star-disk systems (e.g., the dwarf nova SS Cygni) show rapid periodic oscillations in the UV with periods of tens of seconds and high coherence. In this paper, we assess the possibility that these oscillations, called “dwarf nova oscillations” (DNOs), are analogous to diskoseismic modes.

2109: Force-Free Magnetosphere of an Accreting Kerr Black Hole

Authors: Dmitri A. Uzdensky (Princeton University)

I consider a stationary axisymmetric force-free degenerate magnetosphere of a rotating Kerr black hole surrounded by a thin Keplerian infinitely-conducting accretion disk. I focus on the closed-field geometry with a direct magnetic coupling between the disk and the event horizon. I first present a simple physical argument that shows how the black hole's rotation limits the radial extent of the force-free link. I then confirm this result by solving numerically the general-relativistic force-free Grad--Shafranov equation in the magnetosphere, using the regularity condition at the inner light cylinder to determine the poloidal current. I indeed find that force-free solutions exist only when the magnetic link between the hole and the disk has a limited extent on the disk surface. I chart out the maximum allowable size of this magnetically-connected part of the disk as a function of the black hole spin. I also compute the angular momentum and energy transfer between the hole and the disk that takes place via the direct magnetic link. I find that both of these quantities grow rapidly and that their deposition becomes highly concentrated near the inner edge of the disk as the black hole spin is increased.

2110: Hydrodynamical Interaction between Relativistic Winds and Relativistic Accretion Flows

Authors: Jose Erasmo Perez, Sergio Mendoza (Instituto de Astronomia, UNAM)

The interaction of a relativistic wind, produced by a compact object, with a relativistic accretion flow to the object is calculated. This interactions produces a working surface that evolves with time, and under certain circumstances it reaches a steady state. The solutions found were obtained with a semi-analytic model.

2111: Coronal Electron Scattering of Hot Spot Emission around Black Holes

Authors: Jeremy D. Schnittman (Massachusetts Institute of Technology)

Using a Monte Carlo ray-tracing code in full general relativity, we calculate the transport of photons from a geodesic hot spot emitter through a corona of hot electrons surrounding a black hole. Each photon is followed until it is either captured by the black hole or is "detected" by a distant observer. The source is assumed to be a low-energy (~1-2 keV) thermal emitter, isotropic in the rest frame of a massive geodesic test particle. The coronal scattering has two major observable effects: the Comptonization of the photon spectrum due to the high energy electrons, and the convolution of the time-dependent light curve as each photon is effectively scattered into a different time bin. Both of these effects are clearly present in the Rossi X-Ray Timing Explorer (RXTE) observations of high frequency quasi-periodic oscillations (QPOs) seen in black hole binaries. These QPOs tend to occur when the system is in a hard spectral state and also show no evidence for significant power at higher harmonic frequencies, consistent with the "smoothing out" of the light curve by multiple random time delays. We present simulated photon spectra and light curves and compare with RXTE data, allowing us to infer the temperature, density, and size of the coronal region.

2112: Ultraluminous X-ray Sources and Their Host Galaxies

Authors: Roberto Soria (Harvard-Smithsonian Center for Astrophysics/UCL), Mark Cropper (UCL), Chris Copperwheat (UCL), Beverly Smith (East Tennessee State University), Christian Motch (Obs. Strasbourg)

We present some of the latest results from our study of ultraluminous X-ray sources (ULXs) in nearby galaxies. We discuss the possibility of detecting their optical counterparts and using their brightness and colors to constrain the parameters of the accreting systems. We expect very different irradiation effects for the outer disk and companion star if the X-ray source is an intermediate-mass black hole (IMBH) emitting isotropically or a stellar-mass BH with beamed emission. We then focus on the properties of the host galaxies, with particular attention to colliding systems. Old globular clusters, young super star-clusters and mixed-age nuclear clusters are three possible locations for the formation of IMBHs. In particular, an IMBH formed in the nuclear star cluster of a small Scd galaxy may later appear as an off-center ULX if its host galaxy is accreted by a larger galaxy and stripped of its stellar arms. Finally, we apply some of these arguments to two intriguing test cases: the ULXs in the colliding galaxy pair NGC7714/15, and the brightest ULX in the spiral galaxy NGC 4559 (possibly associated to a colliding satellite dwarf)

2113: More Keck Observations of Intermediate-Luminosity X-ray Objects

Authors: Diane Sonya Wong, Alex Filippenko, Ryan Chornock (University of California, Berkeley)

Intermediate-luminosity X-ray objects (IXOs) are non-nuclear point X-ray sources with X-ray luminosities L_x = 10^39-10^41 erg/s. Much interest in them has been generated of late due to the advent of Chandra, and on the theoretical front, viable mechanisms of creating the new class of intermediate-mass black holes (IMBH, 10-1000 solar masses) that must be necessary if accretion onto these IXOs is to obey the Eddington limit. We present the latest results in our ongoing optical follow-up of IXOs. Using Keck optical spectroscopy, we have identified 17 of the IXOs from the Colbert & Ptak (2002) catalog. We discuss our findings in terms of the spiral galaxy-IXO connection.

2114: Superconducting Cosmic Strings that Connected a Charged Black Hole and Considered as Hair of Black Hole

Authors: Ali Riza Akcay (TFI)

This paper describes that the superconducting cosmic strings can be connected to an electrically charged black hole, and can be considered as the hair of black hole. What the no-hair theorems show is that a large amount of information is lost when a body collapses to form a black hole. In addition, the no-hair theorem has not been proved for the Yang-Mills field. This paper proves and claims that the superconducting cosmic strings can be connected to an electrically charged hole when the current inside these strings and black holes approaches the critical value (J --> Jc). Because, this state is the final state of the gravitational collapse, and the event horizon would be destroyed in this state. Therefore, these strings should be considered as hair of the charged black holes, and may be titled as BHCS (Black Hole Connected Strings). This means that at least the charged black holes have the hair. Thus, the no-hair theorem is not applicable for the charged black holes in the state of the critical current (J ~ Jc).

2115: Gravitational Waves from Supermassive Black Hole Coalescence in a Hierarchical Galaxy Formation Model

Authors: M. Enoki (National Astronomical Observatory of Japan), K. T. Inoue (Kinki University), M. Nagashima (Kyoto University), N. Sugiyama (National Astronomical Observatory of Japan)

We investigate the expected gravitational wave emission from coalescing supermassive black hole (SMBH) binaries resulting from mergers of their host galaxies. When galaxies merge, the SMBHs in the host galaxies sink to the center of the new merged galaxy and form a binary system. We employ a semi-analytic model of galaxy and quasar formation based on the hierarchical clustering scenario to estimate the amplitude of the expected stochastic gravitational wave background owing to inspiraling SMBH binaries and bursts owing to the SMBH binary coalescence events. We find that the characteristic strain amplitude of the background radiation is h_c(f) ~ 10^{-16} (f/1 \mu Hz)^{-2/3} for f < ~ 1 \mu Hz provided that SMBHs coalesce simultaneously when host galaxies merge. The main contribution to the total strain amplitude of the background radiation comes from SMBH coalescence events at 0 < Z <1. z at M_{\odot} 10^7 < M_{tot} mass total with binaries SMBH of coalescence associated bursts wave gravitational intense detect might LISA the as such interferometer space-based future a that find also We> ~ 2 at a rate ~1.0 yr^{-1}. Our model predicts that burst signals with a larger amplitude h_{burst} ~ 10^{-15} correspond to coalescence events of massive SMBH binary with total mass M_{tot} ~ 10^8 M_{\odot} at low redshift z < ~ 1 at a rate ~ 0.1 yr^{-1} whereas those with a smaller amplitude h_{burst} ~ 10^{-17} correspond to coalescence events of less massive SMBH binary with total mass M_{tot} ~ 10^6 M_{\odot} at high redshift z > ~ 3$.

2201: INTEGRAL Observation of GRB 030406 in the Compton Mode

Authors: R. Marcinkowski, M. Denis (CBK, Poland), T. Bulik (CAMK, Poland)

GRB 03040 is one of the strongest gamma-ray bursts detected by the INTEGRAL anticoincidence shield. We analyze the IBIS Compton Mode data for this burst and present its localisation, lightcurve and spectrum in the 200 keV to 2.5 MeV range. We also discuss the ongoing analysis of other bursts seen by INTEGRAL in the IBIS Compton mode.

2202: Initiating Short GRBs

Authors: M.A. Aloy, H.-Th. Janka, E. Mueller (Max-Planck-Institut fuer Astrophysik)

We present the results of relativistic hydrodynamic simulations of post-neutron star merger disks as potential candidates to be progenitors of short-lasting gamma-ray bursts. We discuss some of the generic conditions under which a gamma-ray burst can be initiated in this kind of progenitor and the main characteristics of the resulting outflow.

2203: Gamma-Ray Burst Populations

Authors: David Band (NASA Goddard Space Flight Center/UMBC)

With the accumulation of burst databases by different missions, we can begin to understand the burst population. This analysis is fraught with instrumental and statistical problems. I address the sensitivity to the detectors' energy range, the determination of energy distributions, and the consistency of indirect redshift measurements.

2204: Spectral Evolution at Early Stages of Prompt Emission of GRBs

Authors: Anton Chernenko (Space Research Institute, IKI)

Spectral evolution in gamma-rays at very early stages is very similar for most GRBs that are otherwise very different in terms of duration, temporal structure and overall spectral evolution. Using Global fit anslysis for better sensitivity and time resolution we investigated this early spectral evolution with BATSE data. In this paper we present the unified patterns which we found and compare these patters for long and short GRBs. We also discuss how these similarities could be explained based on the dynamics and geometry of relativistic expansion.

2205: Optical Afterglows of Short Gamma-ray Bursts and GRB 040924

Authors: Y. Z. Fan, Bing Zhang (University of Nevada, Las Vegas), Shiho Kobayashi, Peter Meszaros (Pennsylvania State University)

Short-duration Gamma-ray bursts (GRBs) (< 2s) have remained a mystery due to the lack of afterglow detection until recently. The models to interpret short GRBs invoke distinct progenitor scenarios. Here we present a generic analysis of short GRB afterglows, and calculate the optical lightcurves of short GRBs within the framework of different progenitor models. We show that all these optical afterglows are bright enough to be detected by the Ultraviolet and Optical Telescope (UVOT) on board the Swift observatory, and that different models could be distinguished with a well-monitored lightcurve. We also model the lately discovered afterglow data of the short burst GRB 040924. We find that the limited data are consistent with a low medium density environment which is consistent with the pre-concept of the compact-star merger progenitor model if the event is nearby, although the models with a collapsar progenitor are not ruled out.

2206: HETE-2 Observations of X-ray Flashes

Authors: Nobuyuki Kawai (Tokyo Institute of Technology)

X-ray flashes (XRFs) was recognized as a class of cosmological explosive events with the BeppoSAX observations. They have received increasing attention in the past several years. In this paper, we discuss the observational properties of XRFs mostly based on the HETE-2 observations. The low energy threshold (2 keV) and the effective areas at X-ray energies of the instruments make HETE-2 ideal for detecting and studying XRFs. XRFs occupy about one third of the HETE-localized cosmological bursts. We find that the spectral properties of XRFs and X-ray rich GRBs form a continuum with those of ordinary GRBs and suggest that XRFs may represent a further extension of this continuum. On the other hand, we are finding examples of GRBs which seemingly contain a distinct XRF-like components. It may be a problem for the unified view above.

2207: Plasma and Radiation in Inhomogeneous Magnetospheres of Collapsing Stars

Authors: Volodymyr Kryvdyk (Taras Shevchenko Kyiv National University)

The particles acceleration and a non-thermal radiation in the inhomogeneous magnetospheres of collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of charged particles in a magnetosphere are considered. The star magnetosphere compress under collapse and the magnetic field considerably increases. The field structure and particles dynamics in the magnetosphere are depended on from the three factors: particles pressure, collisions between particles and star rotation. As follows from analysis, these factors may be neglected for the magnetosphere of the collapsing star, therefore magnetospheric plasma is frozen in magnetic field and collision-free. To investigate of particle dynamics in magnetosphere the method of adiabatic invariants may by used. The electric field in magnetosphere will accelerate the charged particles which generate radiation in the magnetic field. As follows from the estimation, collapsing stars can by powerful sources of the charged particles and the non-thermal radiation. The radiation flux grows with decreasing stellar radius and it can be observed in the form of radiation burst with duration equal to the stellar collapse time. The radiation flux depends on the distance to the star, its magnetic field, and the particles spectrum in the magnetosphere. The radiation flux is calculated for various collapsing stars with initial dipole magnetic fields and an initial power-series, relativistic Maxwell, and Boltzmann particles energy distribution in the magnetosphere. This radiation can be observed by means of modern astronomical instruments.

2208: Particle Acceleration via Electromagnetic Explosion and Gamma-Ray Bursts

Authors: Edison Liang and Koichi Noguchi (Rice University)

We report latest results from large-scale multidimensional particle-in-cell (PIC) simulations of collisionless electromagnetic plasma explosions and discuss their relevance to prompt GRB emissions. The new simulations include self-consistent radiation, radiative damping and interaction with ambient medium. Differences between electron-positron and electron-ion plasmas will be highlighted. Using ray-tracing we compute the lightcurves, spectral hardness and polarization of radiation as measured by the detector and compare them with BATSE data.

2209: GRB Gamma-ray and Early Afterglow Emission in the External Shock Model

Authors: Erin McMahon, Pawan Kumar, Alin Panaitescu (University of Texas Austin)

We describe our attempt to determine if gamma-ray burst (GRB) and afterglow emissions could both arise in external shocks for simple GRBs, i.e. bursts consisting of at most a few peaks in their lightcurves. We calculate the peak flux and frequency during the GRB for ten well observed bursts using the set of parameters determined by afterglow modelling. We also calculate the emission from the reverse shock heated ejecta during the GRB for these ten bursts, and compare our estimations with early afterglow observations and predictions.

2210: Did a Gamma-Ray Burst Initiate the Ordovician Extinctions?

Authors: Adrian L. Melott (University of Kansas)

A GRB within our galaxy could have catastrophic consequences for the Earth. Extrapolations from the global rate suggest an average interval of 0.1 to 1 Gy for events in which the Earth is irradiated from a distance of a few kpc. Prompt emission would irradiate the surface with UV at least as intense as the present solar IR/visible/UV flux. The atmosphere would become heavily ionized, resulting in major destruction of the ozone layer. Both the prompt UV and that resulting from long-term loss of the ozone layer are destructive to living organisms. The attenuation length of UV in water is tens of meters. There is a strong candidate for a GRB based mass extinction in the late Ordovician, 440 My ago. Planktonic organisms and those animals living in shallow water seem to have been particularly hard hit during this mass extinction.

2211: Relativistic Shocks: Magnetic Field Generation, Particle Accelration, and Emission

Authors: K.-I. Nishikawa (NSSTC), P. Hardee (Univ. of Alabama, Tuscaloosa), C. B. Hededal (Niels Bohr Inst.), G. Richardson (Univ. of Alabama, Huntsville), R. Preece (Univ. of Alabama, Huntsville, NSSTC), H. Sol (Observatore de Paris-Meudon), G. J. Fishman (NASA Marshall Space Flight Center)

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilitie (e.g., the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation from deflected electrons has different properties than synchrotron radiation.

2212: Relativistic Jet Propagation and Dynamics in Massive Progenitor and ISM of GRBs

Authors: Akira Mizuta, Shigehiro Nagataki, and Shin Mineshige (YITP, Kyoto Univ.)

The gamma-ray burst (GRB) is one of the brightest phenomena in the universe. The origin of the GRBs is still a mystery. The relativistic jet from collapsar is one of the weighty hypotheses to explain features observed. This hypothesis is strongly supported by recent GRBs associated with supernovae. We perform numerical relativistic hydrodynamic simulations in 2D. A jet is ejected in the progenitor. It propagates in the star and ISM. The parametric study has been carried out by varying the bulk Lorentz factor and the ratio of the kinetic energy to the total energy of the injected beam to see what kind of jets should be formed around the core.

2214: 3-D Studies of Supernova Explosions

Authors: Lifan Wang (LBNL)

Supernova explosions are intrinsicall 3-D phenomena. The 3-D structure can be probed by spectral polarimetry. Supernovae are usually polarized by asymmetries in the explosion process, off-center sources of illumination, envelopes distorted by rotation or a binary companion, or aspherically distributed circumstellar dust. It is found that both core-collapse and thermonuclear SNe are aspherical. Constraints on explosion models will be discussed as well.

2215: The Role of Absorbtion by Circumburst Material in Determining the GRB Fluence Distribution

Authors: Z. Bosnjak, A. Celotti (SISSA Trieste), F. Longo, G. Barbiellini (Department of Phyics and INFN Trieste), G. Ghirlanda (INAF Merate Observatory)

Based on the recent interpretation of the nature of low-luminosity residual emission in the time evolution of gamma ray bursts as resulting from the Compton scattered photons by the circumburst material, we present the model for the observed BATSE distribution of GRB fluences using the GRB rate (tracing the star formation history) and assuming the distribution of attenuation factors of the external medium.

2216: Cosmological Implications of Compton Tails in Long Duration GRB

Authors: F. Longo, G. Barbiellini (Department of Physics and INFN, Trieste), Z. Bosnjak, A. Celotti (SISSA Trieste), G. Ghirlanda(INAF Merate Observatory)

We will present and discuss the recent suggestion (Barbiellini et al. 2004) of the possible presence of a consistent amount of material (Thomson optical depth ~1) at rest and close to the source at a typical distance of ~10^15 cm with respect to the GRB. The relevance of such interpretation for GRB energetics and its cosmological implications will be outlined.

2217: Relativistic Solutions to the Problem of Jets with Time--Dependent Injection Velocities

Authors: S. Mendoza (Instituto de Astronomia, UNAM), J.C. Hidalgo (Queen Mary College)

We present a model for the motion of the head of a variable relativistic jet. This model is applicable for any variable motion of the flow inside the jet. Under certain variations of the flow velocity, particularly for an oscillating velocity, a group of working surfaces form and travel along the jet, until they merge at its head. The rate of injected energy to the working surface is calculated for the actual luminosity. The solution is applied to a collapsar model in order to compare with the observed luminosity.

2218: Creating Gamma Ray Bursts with a Modified Blandford and Znajek Mechanism

Authors: Erella Opher, Reuven Opher (University of Sao Paulo)

A popular model for the origin of gamma ray bursts is based on the Blandford-Znajek mechanism (BZM). The BZM, as described by Lee et al. and Brown et al., assumes that an electric current extracts energy from the rotation of the Kerr black hole (KBH) and deposits it in a distant load. This mechanism can be shown not to work since: 1)the electric field near the KBH is greater than the critical field for spontaneous electron-positron production; 2)the resistance of the plasma in the load region is much less than that of the KBH, causing the power to be deposited in the KBH instead of in the load; and 3)the back EMF in the load region is equal and opposite to that produced by the KBH. We show here that a modified BZM can avoid the above three problems.

2219: A Search for Prompt Optical Emission of GRB

Authors: A.Pozanenko (Space Research Institute (IKI)), G.Beskin (The Smithsonian Astrophysical Observatory (SAO)), S.Bondar (Kosmoten), A.Biryukov (Sternberg Astronomical Institute Moscow University), K.Hurley (U.C. Berkeley), E.Ivanov (Kosmoten), S.Karpov (SAO), V.Loznikov (IKI), V.Rumyantsev (Crimean Astrophysical Observatory), I.Zolotukhin (Sternberg Astronomical Institute Moscow University)

On the basis of one year of operation (late 2003 and 2004) of a new fast wide-field optical camera we discuss first results of observations. In particular upper limit for the rate of GRB orphans is obtained. The primary purpose of the camera is to perform continuous, alert-independent observations of optical transients (OT) and variable astrophysical sources simultaneously with space-born wide-field X- and gamma-ray telescopes. In particular the camera can detect possible optical precursors to and early prompt emission from Gamma-Ray Burst sources. The main characteristics of the camera are a FOV= 17x20 grad, a frame frequency of 7 1/s, and a limiting magnitude (0.12 s exposure) of 11.5 mag. The bundled software is able to search for and identify various classes of OT’s (non-stationary artificial objects, meteors, variable and new sources) in real-time. We will present first results of the observations and discuss the search strategy, based on synchronous observations of the HETE-2 FOV.

2220: Recent Progress Towards Modeling GRB Prompt Emission

Authors: Robert Preece (University of Alabama in Huntsville)

It is well known that observations of the distributions of the parameters of GRB prompt spectra do not support the first order Fermi shock acceleration model. Recent work modeling the relativistic two-stream instability points the way towards a better understanding of the acceleration of particles as well as the gamma-ray emission. Features of the new scheme include: self-generation of the magnetic field; charge separation and consequent particle acceleration; and small-scale field inhomogeneities leading to particle surfing at small pitch angles. Although there is much work to be done, I will show how these elements add up to a more consistent picture than the standard synchrotron shock model from the point of view of the observations.

2221: The SN 1987A -18 years After

Authors: Oscar Saavedra (Universita’ degli Studi di Torino and INFN Torino)

The SN 1987A becames a milestone in physics and astronomy. From this historic SN explosion we have learned a lot:it was the first experience for humankind to detect neutrinos from extrasolar sources. However, it was not so easy to conciliate the two burst detected by Mt. Blanc for one side and by Kamioka, IMB and Baksan from other side. Besides this problem there appeared also the problem of the very rare coincidences that has been observed and reported at the Fourteenth Texas Symposium 1988 (Amaldi et al.; Chudakov, and M.Aglietta et al.) Recently, a new idea was put forward, (Imshennik and Ryazhaskaya: Astro-ph/0401613) taking into account the rotation of the star during its collapse. Such a model seems to give the answer how and why there was two bangs of the SN 1987A. This presentation will focus on this model and summarizes how such a rotation can account for detection of burst of neutrinos and antineutrinos detected on February 23.

2222: Cosmic-ray Acceleration Through Particle Conversion in Internal and External Shocks in Gamma-Ray Bursts

Authors: E.V. Derishev (Inst. Applied Physics RAS, Russia), F.A. Aharonian (Max-Planck-Institut fuer Astrophysik), V.V. Kocharovsky (Texas A&M University/Inst. Applied Physics RAS), Vl.V. Kocharovsky (Inst. Applied Physics RAS)

We show that the Gamma-Ray Burst fireballs are the most advantageous sites to account for the highest-energy cosmic rays (10^20 eV and higher) via the converter acceleration mechanism. For hadrons, this mechanism exploits photopionic reactions, which convert a proton into a neutron and back, to maximize energy gain per shock crossing and to reduce irreversible particle losses downstream. Considering electrons and positrons, which are also accelerated by the converter mechanism, we analyze how the spectrum of synchrotron and inverse Compton radiation from narrow relativistic jet changes with the observation angle. It is shown that the converter acceleration mechanism allows for numerous modifications of the observed spectrum. In general, the off-axis emission appears to be brighter, has a much harder spectrum and a much higher cut-off frequency compared to the values derived from Doppler boosting considerations alone. The effect of beam-pattern broadening at high frequencies can be used in searches for off-axis Gamma-Ray Bursts.

2223: Numerical Simulation of Hydrodynamic Instability in a Rotating Protoneutron Starby Supernova Explosion II Type

Authors: Sergey D. Ustyugov (Keldysh Institute of Applied Mathematics)

Three-dimensional numerical simulations of the development of large-scale hydrodynamical instability in a rotating protoneutron star during a type II supernova explosion is presented. On the last stage of collapse of the iron core of a star the process of nonequilibrium neutronization of matter provides high entropy and great mean energy of the neutrinos in the central part of the protoneutron star. The hydrodynamically ustable configuration of a protoneutron star is formed. The calculation results show that, ~3 ms after the onset of a finite entropy perturbation in the center of the protoneutron star, a bubble of hot core material forms, giving rise to convective motions. The bubble of hot neutron material rises toward the stellar surface, while cooler material sinks toward its center. Most of the initial entropy perturbation develops in the form of two bubbles, which rise toward the surface along the star's rotation axis over a time ~1 ms. Neutrino transfer via convective flow to the surface of a proto-neutron star is numerically simulated. The evolution of the neutrino distribution in a heated region rising from the center of the proto-neutron star to its surface is simulated using a kinetic equation with a Uehling–Uhlenbeck collision integral in a uniform, isotropic approximation. The composition of the matter in the region under consideration changes due to the "burning" of electrons and protons by beta processes. The simulation results enable the estimation of the characteristic time required for the rising medium to become optically thin to neutrinos and the characteristic spectrum of the neutrinos that are emitted. Estimates of the energy of the neutrino emission arriving at the shock wave front as the bubble rises toward the neutrinosphere suggest that large-scale convection is capable of supporting a diverging shock wave, leading to the ejection of the supernova envelope. Observations of the central regions of SN 1987A provide evidence for the presence of two large-scale ejections, which are in good agreement with our model when the rotation of the star is taken into account. Gravitational radiation arising during the formation of a protoneutron star is studied. Convective large-scale motions of material give rise to an inhomogeneous mass distribution inside the star. Variable asymmetry appears in the mass distribution, and this causes gravitational radiation. The characteristic masses of bubbles are 0.01M and the radial velocities reach ~ 0.1c. The energy radiated in the form of gravitational waves in one cycle of bubbles floating to the surface is ~ 10(– 2)Mc2 – 10(– 10) Mc2. Such cycles occur repeatedly as the neutron star cools. This phase can last up to seconds. The total energy radiated in the form of gravitational radiation can reach 10(– 1) Mc2.

2224: RAM: A Relatavistic Adaptive Mesh Refinement Hydrodynamics Code

Authors: Weiqun Zhang (KIPAC) and Andrew MacFadyen (Institute for Advanced Study)

We have developed a new computer code, RAM, to solve the conservative equations of special relativistic hydrodynamics using adpative mesh refinement. RAM includes physical equations of state, neutrino cooling and nuclear physics. It is intended initally to address open theoretical questions in the study and Gamma-Ray bursts (GRBs) and supernova explosions.

2225: Gamma-Ray Burst Supernovae

Authors: S. Klose, A. Zeh (Thueringer Landessternwarte Tautenburg, Germany) and D. H. Hartmann (Clemson University, Clemson, SC) (2) Clemson University, Clemson, SC

We highlight the physical association between long-duration GRBs and core-collapse supernovae. So far, in 2 to 3 cases we have spectrosocopic evidence for SN light in GRB afterglows. In addition, via photometry in about 10 cases extra light has been found in afterglows starting about 2 weeks after the corresponding burst that can be attributed to an underlying SN component. Such bumps have been found in afterglows up to redshifts of about z=1. We discuss this new class of GRB SNe as a potential tool to explore the high-z universe.

2303: Gamma-rays from Compact Massive Binaries

Authors: Wlodek Bednarek, Agnieszka Sierpowska (University of Lodz, Poland)

We calculate the gamma-ray phase dependent spectra and fluxes produced in cascades initiated by leptons injected by young pulsars into the soft radiation field of a massive companion star. In is concluded that the features of the gamma-ray emission from such compact binaries should allow to obtain important information on the acceleration of particles by the pulsars and on the interaction of the pulsar and the massive stellar winds.

2304: Using the EXIST Active Shields for Earth Occultation Observations of X-ray Sources

Authors: Colleen A. Wilson, Jerry Fishman (NASA Marshall Space Flight Center), Jae-Sub Hong, Jonathan Grindlay (Harvard-Smithsonian Center for Astrophysics), Henric Krawczynski (Washington Univ. in St. Louis)

The EXIST active shields, now being planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors; and they will have a good geometry on the spacecraft for viewing both the leading and trailing Earth's limb for occultation observations. These occultation observations will complement the imaging observations of EXIST and can extend them to higher energies. Earth occultation observations of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for this method. With BATSE, a catalog of 179 X-ray sources was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5-sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (galactic and extragalactic.) This poster will describe the Earth occultation technique, summarize the BATSE occultation observations, and compare the basic observational parameters of the occultation detector elements of BATSE and EXIST.

2305: INTEGRAL Observations of OAO1657-415: Gamma Ray Tomography of a B Supergiant

Authors: T. Bulik(CAMK, Poland), M. Denis, R. Marcinkowski (CBK, Poland)

INTEGRAL has been monitoring the eclispsing X-ray pulsar for over one year. We present the results of these obsevations. The 38 s pulsations have been detected. A careful analysis of the eclipse lightcurve allows to model the density profile in th outer atmosphere and stellar wind of the companion, a B supergiant. We also find that the models favor the inclination of the system close to the lower bound, i.e i=60-70 degrees.

2306: Modelling Light Curves of Millisecond Period X-ray Pulsars

Authors: Coire Cadeau, Sharon M. Morsink (University of Alberta)

Light curves of X-ray pulsars reveal characteristics of the underlying neutron star and emission region. To accurately interpret observations of millisecond period X-ray pulsars, one requires theoretical models of such light curves which fully account for general relativity and timing effects. I will discuss how these models can be calculated and some common approximation techniques, and demonstrate how characteristics of the pulsar are manifested in these models.

2307: Upper Limits on Dying Pulse Train Events from Cygnus XR-1

Authors: J. F. Dolan (NASA Goddard Space Flight Center), Julia N. Holland (Univercity of California, Irvine)

Dying pulse trains (DPT's) - a series of decreasing intensity photometric pulses with monotonically decreasing separations - are a signature of an event horizon around a black hole with an accretion disk in GR (Stoeger, MNRAS, 190, v715, 1980; Dolan, Science, v292, 1079, 2001). Two pulse trains with the characteristics of DPT's were discovered in UV photometry of Cygnus XR-1 obtained with the Hubble Space Telescope (Dolan, PASP, v113, 974, 2001). A search of 7 hours of (1 - 10) keV X-ray photometry of Cygnus XR-1 using RXTE has detected many X-ray pulses arising from the inner region of the accretion disk, but no DPT's. Upper limits on the DPT event rate are given as a function of X-ray luminosity. The region of event-parameter space ruled out by these observations begins to constrain the physics of the environment near event horizons in black holes.

2308: Line-Driven Winds Near Compact Objects

Authors: Anton V. Dorodnitsyn (Space Research Institute, Moscow)

A general physical mechanism of the formation of line-driven winds at the vicinity of strong gravitational field sources is investigated in the frame of General Relativity. We argue that gravitational redshifting should be taken into account to model such outflows. The generalization of the Sobolev approximation in the frame of General Relativity is presented. We consider all processes in the metric of a nonrotating (Schwarzschild) black hole. The radiation force that is due to absorbtion of the radiation flux in lines is derived. It is demonstrated that if gravitational redshifting is taken into account, the radiation force becomes a function of the local velocity gradient (as in the standard line-driven wind theory) and the gradient of g00, and if the gravitational filed is described by the potential (Newtonian or Paczynski-Wiita modified potential) as a function of the local velocity gradient and the gradient of the gravitational potential. A comparison with the case when gravity is described by potential (Newtonian or Paczynski-Wiita modified potential) is presented and confronted with that of GR description. We derive a general relativistic equation of motion describing such flow. A solution of the equation of motion is obtained and confronted with that obtained from the Castor, Abbott & Klein (CAK) theory. It is shown that the proposed mechanism could have an important contribution to the formation of line-driven outflows from compact objects and in particular discuss applications to AGN.

2309: Spectral-Temporal Correlations Observed in Black Hole Systems

Authors: Ralph Fiorito (University of Maryland/NASA-GSFC), Lev Titarchuk (Naval Research Laboratory/GMU/NASA-GSFC)

We have studied the relationship between characteristic frequencies in the power density spectra and energy spectral properties, in particular the power law index, in black hole (BH) candidate systems with masses ranging from 10 to 1000 solar masses. We show how the correlations observed between the low and high frequency quasi-periodic oscillations, the break frequency and the power law spectral index can be used to infer important physical characteristics of the BH, in particular the BH mass. Several examples are presented for galactic and extragalactic BH candidate sources.

2310: H.E.S.S. Observations of Microquasars

Authors: W. Benbow, S. Funk (Max-Planck-Institut fuer Kernphysik, Heidelberg), P. Chadwick (University of Durham), G. Dubus (Laboratoire Leprince-Ringuet, IN2P3/CNRS, Ecole Polytechnique), D. Horns (Max-Planck-Institut fuer Kernphysik), I. Latham (University of Durham), M. de Naurois (Laboratoire de Physique Nuclaire et de Hautes Energies, IN2P3/CNRS, Universites Paris), G. Rowell (Max-Planck-Institut fuer Kernphysik) for the H.E.S.S. Collaboration

Stellar mass black holes display surprising similarities with the phenomena commonly seen in supermassive black holes. Pursuing the analogy, some X-ray binaries may display blazar-like behaviour with emission of very high energy gamma-rays. We report on H.E.S.S. observations at energies > 100 GeV of possible candidate 'microblazars'.

2311: Radio-Loud and Radio-Quiet, Gamma-ray Pulsars from the Galactic Plane and the Gould Belt

Authors: Peter L. Gonthier (Hope College), Robert Van Guilder (University of Colorado at Denver), Alice K. Harding (NASA Goddard Spaceflight Center), Isabelle Grenier (Universite' Paris VII/Service d'Astrophysique, CEA, Saclay), Christophe Perrot (SLAC)

We present recent results of a population synthesis study in the polar cap model that includes the Parkes multibeam pulsar survey, realistic beam geometries for radio and gamma-ray emission from neutron stars born in the Galactic plane as well as the local OB association known as the Gould Belt. We include nine radio surveys to normalize the simulated results from the Galactic plane to the number of radio pulsars observed by these surveys. In normalizing the contribution of the Gould Belt, we use results from a recent study that indicates a supernova rate in the Gould Belt of 3 to 5 times that of the local region of the Galactic plane leading to ~120 neutron stars in the Gould Belt during the last 5 Myr. Our simulations include the evolution of the Gould Belt during the past 5 Myr. We will discuss recent results of our simulations predicting the numbers of radio-quiet (below threshold of radio surveys) and radio-loud, gamma-ray pulsars from the Galactic plane and the Gould belt observed by EGRET, AGILE and GLAST. Our results suggest that many of the unidentified EGRET sources could be radio-loud and radio-quiet, gamma-ray pulsars that EGRET should have observed as point sources from the Galactic plane and some from the Gould Belt. We express our gratitude for the generous support of the Research Corporation (CC5813), of the National Science Foundation (REU and AST-0307365) and the NASA Astrophysics Theory Program.

2312: Thermoelectric Effects and Magnetic Field Evolution in Neutron Stars

Authors: Wynn C.G. Ho (KIPAC/Stanford), Roger D. Blandford (KIPAC/Stanford), Lars Hernquist (Harvard-Smithsonian CfA)

Neutron stars are thought to be born with a magnetic field that is frozen in during its initial gravitational collapse. Whether this initial field decays or not is uncertain. We investigate a method for magnetic field evolution in the crust, specifically, whether the effect of a heat flux through the outer layers of a neutron star can amplify, or to what degree it can alter, a seed magnetic field. Previous work suggested that a thermal flux may yield a complicated, evolving pattern of magnetic flux on the surface of the star. It is possible that this thermoelectric effect could be related to the observed properties of neutron stars, in particular, to the generation of magnetar field strengths, B > 10^14 G. We extend the previous linear, perturbative analysis with a more accurate, non-linear calculation.

2313: Taking the Pulse of the Shortest Orbital Period Binary System: RXJ0806.3+1527

Authors: Israel, G.L. (INAF - OA Roma), et al.

In 2002 we proposed RXJ0806.3+1527 to be a 321s orbital period (the shortest known) double white dwarf binary system. According to the double degenerate binary (DDB) scenario this source is expected to be one of the strongest Gravitational Wave (GW) emitter candidates, well within the capabilities of the forthcoming LISA mission. In the last four years RXJ0806.3+1527 has been studied in great details, through multiwavelength observational campaigns and from the point of view of data analysis result interpretations. We will show here the timing results obtained thanks to a 4-year long optical monitoring campaign carried out by the Very Large Telescope (VLT) and the Telescopio Nazionale Galileo (TNG) which allowed us to detect and study the orbital period derivative of the 321s modulation, to detect the linear polarisation, and to study the broad band energy spectrum. The VLT/TNG observational strategy we used allowed us to rely upon a P-Pdot coherent solution which we finally extended backward to the 1994 ROSAT observation of RXJ0806.3+1527. The implication of our studies will be reviewed on the light of the proposed theoretical models.

2314: High-Frequency QPOs in Black Holes as a Resonance

Authors: Wlodek Kluzniak (University of Zielona Gora)

High frequency quasi-periodic oscillations in Galactic black holes can be understood as non-linear resonant oscillations of an accretion disk in the Kerr metric. The highest-frequency QPOs observed are likely caused by incompressible vertical oscillations of a torus whose X-ray emission is lensed at the source. The kHz QPOs in neutron stars may be caused by similar oscillations excited by a periodic disturbance (e.g., a rotating magnetic dipole). The resonance model of high-frequency QPOs in black holes will be summarized and updated in this presentation.

2315: Multiwavelength Observations and State Transitions of an Ultraluminous Supersoft X-ray Source: Evidence for an Intermediate-Mass Black Hole

Authors: Albert Kong (Harvard-Smithsoinan Center for Astrophysics)

We report the results of X-ray/optical/radio observations of an ultraluminous supersoft X-ray source in M101. The source was observed in a low luminosity state (Lx~1e37 erg/s) between 2004 January and May and the low-state X-ray spectra were hard. During 2004 July, the source underwent a strong outburst with a peak bolometric luminosity of 1e41 erg/s. The outburst spectra were very soft and can be fitted with a blackbody model with temperatures of 50-100 eV. In two of the observations, absorption edges at 0.33 keV, 0.56 keV, 0.66 keV, and 0.88 keV were found. The source returned to the low state in 2004 September. While there is no radio emission detected, the optical counterpart is a blue variable. Its high-state luminosity, its variability, its soft high-state spectrum, and its pronounced spectral changes, all suggest that the source is a strong intermediate-mass black hole candidate.

2316: Cygnus X-1: Tracking 0.1-10 Hz Characteristic Frequencies Through the State Transitions

Authors: Magnus Axelsson, Luis Borgonovo, Stefan Larsson (Stockholm Observatory)

Analyzing the archival data from the Rossi X-Ray Timing Explorer (RXTE), we study the power density spectra (PDS) of Cygnus X-1 from 1996 to 2003. Applying a model with few components we show good fits to the PDS between 0.01 Hz and 25 Hz, and are able to track their evolution through all spectral states of the source. We confirm the relation between characteristic frequencies previously seen in both neutron star and black-hole candidate systems, and show the changes in this relation during transitional and soft states of the source. Applying a model of relativistic precession to explain the frequency relation shows remarkable agreement with the hard state data, but cannot explain the behavior in the soft state without additional assumptions.

2317: Warm Stellar Matter with and without Trapped Neutrinos

Authors: Menezes D.P (Universidade Federal de Santa Catarina - Brazil) and Providência C. (University of Coimbra - Portugal)

The properties of hybrid stars formed by hadronic and quark matter are described by appropriate equations of state in the framework of relativistic mean field theory. The phase transition to a deconfined quark phase is investigated either for neutrino free or neutrino trapped matter. Depending on the model chosen the mixed phase of hadrons and quarks may or may not exist. Maximum baryonic masses are always higher when neutrinos are present. The presence of delta mesons is also investigated and it influences the amount of neutrinos present in the star. This fact has implications in the cooling of a protoneutron star since the amount of neutrinos defines whether the star decays into a low mass black hole or into a neutron star.

2319: Effects of Accretion Column Structure on Observed Pulse Shapes

Authors: Denis A. Leahy (University of Calgary)

Observed x-ray pulse shapes of neutron stars are complex, and have been difficult to model. The pulse shape of Her X-1, with extra information from the accretion disk occultation, has been successfully modeled (Leahy, 2004, MNRAS, 348, 932) with an accretion column, including light bending. Here are explored the effects of vertical and azimuthal structure of the accretion column on model observed pulse shapes.

2320: Pulse Emission from Relativistically Collapsing Objects

Authors: Valeri Frolov(University of Alberta) and Hyun Kyu Lee(University of Alberta/Hanyang University)

Possible phase transitions at the densities higher than expected in the neutron star are widely discussed in the literature. Such a transition would be accompanied by the emission of light particles including photons and neutrinos. If such a pulse of light particles is emitted during the collapse of a massive star or a neutron star with supercritical mass, its time of arrival to the distant observer, redshift and bending angle would be affected by the strong gravitational field. We study a toy model supposing that a pulse of radiation is emitted from the surface of a collapsing sphere. We are trying to find such robust features that would allow a distant observer to distinguish the burst-like events from the continuous in time emission. We develope an analytic formula for the time of arrival at a distant observer, which approximate the exact intergral very well with the accuracy of less than 1 % error for R > 2R_g in Schwarzschild metric. We discuss the observational characteristics of the light curve for an isotropic pulse emitted from a collapsing object.

2321: The Chaotic Behavior of the Black Hole System GRS 1915+105

Authors: R. Misra (Inter-University Center for Astronomy and Astrophysics), K.P. Harikrishnan (Cochin College), B. Mukhopadhyay (Harvard-Smithsonian Center for Astrophysics), G. Ambika (Maharajas College), A. K. Kembhavi (Inter-University Center for Astronomy and Astrophysics)

The rapid variability of black hole X-ray binaries originates in the inner regions of an accretion disk where General Relativistic effects are important. However, the nature of this variability is still uncertain. A modified non-linear time series analysis technique, which computes the correlation dimension D_2, is used to analyze the X-ray light curves of the black hole system GRS 1915+105 in all twelve temporal classes. For four of these temporal classes D_2 saturates to approx 4-5 and is distinct from surrogate data. This indicates that the underlying dynamical mechanism is a low dimensional chaotic system. The detection of chaos in a black hole system, opens a new window towards our understanding of these systems and raises the possibility that QPO are limit cycles and that spectral states are fixed point attractors which under certain conditions are unstable, leading to state transitions.

2322: Accretion Mode Changes in Centaurus X-3

Authors: B. Paul, U. Mukherjee, H. Raichur (Tata Institute of Fundamental Research)

We discovered a unique feature of two different accretion modes in the high mass X-ray binary pulsar Cen X-3. The RXTE-ASM light curve of Cen X-3 shows many episodes of high and low X-ray intensity. The high intensity phases last between a few to upto 100 days and the separation between two outbursts also varies widely. One remarkable feature deduced from the RXTE-ASM light curves is that there are two distinct spectral states of Cen X-3. During each episode of high intensity, the source remains in only one of these two spectral states. During 1996-2000, all the high intensity episodes showed a low hardness ratio which changed in December 2000 and continued till May 2004, after which, the source made a transition back to its previous state. It is also found that most of the soft outbursts reach a nearly constant peak flux in the 5-12 keV band.

2323: Stability of Strange Stars (SS) Derived froma Realistic Equation of State

Authors: Monika Sinha (Presidency College, India), Jishnu Dey (Moulan Azad College, India), Mira Dey (Presidency College, India), Subharthi Ray (IUCAA, India), Siddhartha Bhowmick (Barasat Government College, India)

A realistic EOS leads to strange stars (ReSS) which are compact in the mass radius plot, close to the Schwarzchild limiting line (M. Dey, I. Bombaci, J. Dey, S. Ray and B. C. Samanta, PLB 438, (1998) 123). Many of the observed stars fit in with this kind of compactness, irrespective of whether they are X-ray pulsars, bursters or soft gamma repeaters or even radio pulsars. We carry out a stability analysis under radial oscillations and compare with the EOS of other SS models. We find that the ReSS is stable and an M-R region can be identified to that effect.

2324: Monte Carlo Simulator to Study High Mass X-ray Binary System

Authors: Shin Watanabe, Fumiaki Nagase, Tadayuki Takahashi (ISAS/JAXA), Masao Sako, Steve M. Kahn (KIPAC/Stanford), Manabu Ishida, Yoshitaka Ishisaki (Tokyo Metropolitan University), Frederik Paerels(Columbia University)

The grating spectrometers on-board Chandra and Newton have provided high-resolution X-ray spectra of many astrophysical sources. They have resolved forests of X-ray emission lines, Doppler shifted lines and distinguishing profiles like Compton shoulders. The analysis of these features provides unambiguous information on physical conditions in astrophysical sources, however, simple model fitting techniques used in the past are not suffice. We have been developing a Monte Carlo simulator for astrophysical phenomenon which incorporate the transportation of X-rays in photoionized plasma. We applied the code to X-ray spectra of high mass X-ray binaries, Vela X-1 and GX 301-2, obtained with Chandra HETGS. The asymmetric geometry of the binary system is taken into account. By the simulation, we have successfully reproduced many emission lines observed from Vela X-1. The ionization structure and the matter distribution in the system are deduced. For GX 301-2, we have derived the physical parameters of material surrounding the neutron star from fully resolved Compton shoulder in the iron K-alpha line.

2325: Magnetosphere of Oscillating Neutron Star

Authors: Andrey N. Timokhin (Sternberg Astronomical Institute)

Pulsar "standard model" of rotating magnetized conducting sphere surrounded by plasma is generalized in its essential parts for the case of oscillating star. Goldreich-Julian charge density, electromagnetic energy losses as well as polar cap scenario of particle accelerations are considered. Despite similarities, there are substantial differences between magnetospheres of rotating and oscillating stars. Distortion of particle acceleration mechanism in radiopulsars by neutron star oscillations (excited by a strong glitch, for example) is discussed.

2326: Late-breaking News (1)

Authors: Scott M. Ransom

(none)

2327: Late-breaking News (2)

Authors: D. K. Galloway

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2401: Evidence for a New Source of TeV Gamma Rays from Angular Correlation Studies of the Milagro and Tibet Northern Sky Surveys

Authors: Robert Atkins, David Kieda, Stephan LeBohec, Gary Walker(University of Utah)

We have analyzed the directional cross-correlation of marginally significant "hot-spots" between the northern sky TeV gamma-ray surveys performed by the Milagro group and the Tibet Air Shower Array. We have found that, while the individual observations produced no significant excesses, there does exist a correlation in the locations of hot-spots in the two surveys that is statistically significant for angular separations less than 1.5 degrees. We find this to be an indication that previously unobserved sources of TeV Gamma rays would exist just below the sensitivity of both experiments. In addition to this, recent results from the Milagro group indicate the possible presence of a diffuse source of gamma rays in association with one of their "hot-spots". We will present the results of our analysis on the correlations, and we will show that the diffuse source candidate observed by Milagro could be associated to a large molecular cloud in the region of the Cygnus arm.

2402: Supporting the GLAST User Community

Authors: David Band (NASA Goddard Space Flight Center/UMBC) for the GLAST Science Support Center

The Gamma-ray Large Area Space Telescope (GLAST) Science Support Center (GSSC) is the scientific community's interface with GLAST. The GSSC will provide data, analysis software and documentation. In addition, the GSSC will administer the guest investigator program for NASA HQ. Consequently, the GSSC will provide proposal preparation tools to assist proposers in assessing the feasibility of observing sources of interest.

2403: Observation of the Giant Radio Galaxy M87 at TeV Energies with the H.E.S.S. Cherenkov Telescopes in Namibia

Authors: M. Beilicke, R. Cornils, G. Heinzelmann (Institut fuer Experimentalphysik, Univ. Hamburg), D. Horns (Max-Planck-Institut fuer Kernphysik), M. Raue (Institut fuer Experimentalphysik, Univ. Hamburg), J. Ripken (Institut fuer Experimentalphysik, Univ. Hamburg), M. Tluczykont (Laboratoire Leprince-Ringuet) for the H.E.S.S. Collaboration

The giant radio galaxy M87 was observed at TeV energies with the Cherenkov telecopes operated by the H.E.S.S. collaboration (High Energy Stereoscopic System) in the year 2003 during the comissioning phase and in 2004 with the full 4 telescope setup. The observations were motivated by the measurement of the HEGRA collaboration which reported a 4.7 sigma excess of TeV gamma-rays from the direction of M87. The results of the H.E.S.S. observations indicating a possible variability of TeV gamma-ray emission from M87 (compared to the HEGRA result) are presented.

2404: First detection of the Binary System PSR B1259-63 at TeV Energies with the H.E.S.S. Cherenkov Telescopes

Authors: M. Beilicke (Institut fuer Experimentalphysik, Univ Hamburg), B. Khelifi, L. Costamante, C. Masterson (Max-Planck-Institut fuer Kernphysik, Heidelberg, Germany), M. de Naurois, L. Rolland (Laboratoire de Physique Nucleaire et de Hautes Energies, Univ. Paris, France), S. Schlenker (Institut fuer Physik, Humbold Univ. zu Berlin) for the H.E.S.S. collaboration

In February/March 2004 the binary system PSR B1259-63/SS 2883 consisting of a 48ms pulsar orbiting its Be companion star on a highly eccentric orbit was for the first time detected at TeV energies with the H.E.S.S. Cherenkov telescopes. Following this detection close to the periastron passage of the binary system the observation campaign on this unique object has been extended up to June 2004. The recorded lightcurve shows clear variations making PSR B1259-63 the first detected variable galactic TeV source. Contemporaneous observations at other wavelengths have been triggered by the H.E.S.S. detection which are also presented.

2405: Detection of a Yet Unidentified TeV Gamma-ray Source HESS J1303-631 Close to the Galactic Plane with the H.E.S.S. Cherenkov Telescopes

Authors: M. Beilicke (Institut fuer Experimentalphysik, Univ. Hamburg), B. Khelifi, L. Costamante, C. Masterson (Max-Planck-Institut fuer Kernphysik), M. de Naurois (Laboratoire de Physique Nucleaire et de Hautes Energies, Univ. Paris), M. Raue (Institut fuer Experimentalphysik, Univ. Hamburg), L. Rolland (Laboratoire de Physique Nucleaire et de Hautes Energies, Univ. Paris), S. Schlenker (Institut fuer Physik, Humbold Univ. zu Berlin) for the H.E.S.S. Collaboration

Following the detection of the binary system PSR B1259-63/SS 2883 at TeV energies (see a parallel poster) another TeV source being named 'HESS J1303-631' has been discovered serendipitously close to the galactic plane in the same field of view. The data were taken between February and June 2004. Up to now, no counterpart at other wavelengths was found. This makes HESS J1303-631 the second unidentified TeV source following TEV J2032+4130 discovered in the Cygnus region by the HEGRA collaboration. Results on the new TeV source are presented.

2406: Blazar Observations with CELESTE

Authors: Elisabeth Brion (CENBG, France) for the CELESTE Collaboration

The CELESTE atmospheric Cherenkov detector, running until June 2004 at the Themis solar facility, has observed compact sources such as pulsars and blazars. We will take stock of the experiment, in particular regarding the last improvements of the detector simulation and data analysis. These changes provide us with a new analysis of old data with smaller uncertainties. We present here the results obtained for some blazars observed during the last six years with different configurations of the experiment.

2407: Small Molecular Clouds at High Latitudes as Gamma-Ray Sources for GLAST

Authors: Seth W. Digel (SLAC), Diego F. Torres (LLNL), Thomas M. Dame (Harvard-Smithsonian CfA)

The sensitivity of the Large Area Telescope (LAT) on the forthcoming GLAST mission will be so much greater than previous high-energy gamma-ray missions that small molecular clouds at intermediate and high Galactic latitudes (|b| > 10 deg) will be detected in the light of diffuse gamma-ray emission from cosmic-ray interactions. These clouds are small, typically subtending less than 1 degree with masses ~10-100 solar and distances ~150 pc, and many are only now being discovered with sensitive, well-sampled, unbiased surveys of CO away from the Galactic equator. On the order of 100 such clouds will be detected by the LAT. Most will be near the detection limit (which depends on angular size) and many will in fact be detected but unresolved by the LAT, i.e., indistinguishable from point sources. We present predictions for the detectability of recently-cataloged clouds. As a gamma-ray source class, they will clearly have a Galactic distribution and be steady emitters, but identifications of these sources as molecular clouds rather than potentially more exotic gamma-ray phenomena will require more extensive and finely-sampled CO surveys at high latitudes.

2408: Discovery of Diffuse Hard X-ray Emission and Its Relation to High Energy Particles in the Massive Star Forming Region

Authors: Yuichiro Ezoe (ISAS/JAXA), Yasunobu Uchiyama (Yale University), Kazuo Makishima (University of Tokyo)

Massive stars (>10 solar mass) affect their environments profoundly by ultra-violet photons and fast stellar winds. We analyzed the Chandra data of the representative massive star-forming region NGC 6334. After removing hundreds of point sources, we found the extended X-ray emission (5x9 pc2 and 2e33 erg/s in the 0.5-8 keV luminosity). After estimating unresolved point sources, ~90% of the emission was concluded as diffuse in nature. In tenuous cloud regions, its spectra tend to be represented by thermal emission of several keV. In contrast, in more dense regions, they exhibit flat continua (a photon index of ~1), suggesting bremsstrahlung emission by sub-MeV electrons. All the results can be explained in terms of strong shocks of the stellar winds from young OB stars.

2409: EUSO: an Experiment to Study Extreme Energy Cosmic Rays from Space

Authors: P. Galeotti (University and INFN, Torino) on behalf of the Euso Collaboration)

The “Extreme Universe Space Observatory– EUSO” is an international mission to be flown on-board the Columbus module on the International Space Station. EUSO will investigate the nature and origin of Extreme Energy Cosmic Rays (EECRs) while opening a new window to the Universe: the High Energy Neutrino Astronomy. EUSO will offer a unique possibility to discriminate the production mechanisms, namely Bottom-Up or Top-Down, of EECRs. EUSO will observe the fluorescence signal (330-400 nm operating wavelengths) looking to the Nadir at the dark Earth’s atmosphere under a 60° full field-of-view from its location, as external payload, onboard of the ISS, about 400 km altitude. The Čerenkov signal, diffused when the shower hits ground or the top of a cloud, will be also imaged. EUSO will measure the primary energy, arrival direction and composition of EECRs, using a target volume far greater than is possible from the ground. Such data will shed light on the origin of EECRs, on the sources that are producing them, on the propagation environment from the source to the Earth, and, possibly, on the particle physics mechanisms at energies well beyond the ones achievable in man-made accelerators. In the case of Super-GZK, about 3.000 showers are expected to be observed above 10**20 eV. For the GZK case, the number of events observed for energies above 10**20 eV is still about 500. This implies that the GZK decrease can be precisely measured as well as the GZK recovery.

2410: Rapid Correlated X/TeV Variability in Mkn421

Authors: Berrie Giebels, Guillaume Dubus (LLR Ecole Polytechnique), Bruno Khelifi (MPI Heidelberg)

A very high emission state of Mkn421 and its correlated variability in the X-ray and TeV bands are reported. The lightcurve and spectral variability are analyzed and we specify how physical parameters derived in the context of the SSC model are obtained for this highly interesting episode.

2411: Multiwavelength Observations of the BL Lac PKS 2155-304 with the H.E.S.S. Cherenkov Telescopes

Authors: Berrie Giebels (LLR Ecole Polytechnique) for the H.E.S.S. collaboration

The BL Lac object PKS 2155-304 was subjected to an intensive 2-month multi-wavelength survey in 2003, featuring for the first time simultaneous radio-optical-X-GeV/TeV observations on this object. Continuous detections indicate that H.E.S.S. possibly sees the for the first time a quiescent level in a BL Lac, and broadband modeling of the spectral energy distribution constrained by a well-measured VHE spectrum sheds new light on the properties of this source.

2412: Non--Fermi Power law Acceleration in Astrophysical Plasma Shocks

Authors: Troels Haugbølle (NBI), Christian B. Hededal (NBI), Jacob Trier Frederiksen (Stockholm Observatory), Aake Nordlund (NBI)

Collisionless plasma shock theory, which applies for example to the afterglow of gamma ray bursts, still contains key issues that are poorly understood. We have studied charged particle dynamics in a highly relativistic collisionless shock numerically, using ~10^9 particles. We find a power law distribution of accelerated electrons, which upon detailed investigation turns out to originate from an acceleration mechanism that is decidedly different from Fermi acceleration. The electrons are accelerated and decelerated instantaneously and locally; a scenery that differs qualitatively from recursive acceleration mechanisms such as Fermi acceleration. The slopes of the electron distribution power laws are in concordance with the particle power law spectra inferred from observed afterglow synchrotron radiation in gamma ray bursts, and the mechanism can possibly explain more generally the origin of non--thermal radiation from shocked inter-- and circum--stellar regions and from relativistic jets.

2413: Radio Detection of High-Energy Cosmic Rays: LOPES

Authors: Andreas Haungs (Forschungszentrum Karlsruhe) for the LOPES Collaboration

The detection of radio pulses emitted in the atmosphere during the air shower development of high-energy primary cosmic rays is the task of the LOPES project. To test this technology and to demonstrate its ability to measure air showers a 'LOFAR Prototype Station' (LOPES) is set up to operate in conjunction with an existing air shower experiment (KASCADE-Grande). LOFAR (Low Frequency Array) is a new digital radio interferometer under development using high bandwidth ADCs and fast data processing to filter out most of the interference. By storing the whole waveform information in digital form transient events like air showers can be analysed even after they have been recorded. The LOPES antennas are operating in the frequency range of 40-80 MHz. For several air-shower events a coincident and coherent signal has been found and a preliminary analysis has already been performed. The main goal of further investigations is to calibrate the radio signal with help of the observables of the individual air-showers given by KASCADE-Grande.

2414: Cosmic Rays in the PeV Energy Range: KASCADE-Grande

Authors: Andreas Haungs (Forschungszentrum Karlsruhe) for the KASCADE-Grande Collaboration

Recent results from the multidetector set-up KASCADE on measurements of cosmic rays in the energy range of the so called knee (at ~3 PeV) are presented. The multidimensional analysis of the air shower data indicates a distinct knee in the energy spectra of light primary cosmic rays and an increasing dominance of heavy ones towards higher energies. This provides, together with the results of large scale anisotropy studies, implications for discriminating astrophysical models of the origin of the knee. To improve the reconstruction quality and statistical accuracy at higher energies, where the knee of the heavy primaries is expected at around 100 PeV, KASCADE has recently been extended by a factor 10 in area to the new experiment KASCADE-Grande.

2415: Up-to-Date Proton-Proton Interaction Modeling and Galactic Gamma-ray, Positrons and Anti-Proton Spectra

Authors: T. Abe, T. Kamae, N. Karlsson, T. Koi, and T. Mizuno (SLAC)

We have calculated gamma-ray, positron, anti-proton and neutrino spectra from high energy pp interactions in the astrophysical environment. The calculation includes the diffraction dissociation and incorporates the Feynman scaling violation for the first time. We found that the diffractive process makes light-mass secondary particle spectra harder than the incident proton spectrum, and, that the scaling violation produces more pions and anti-protons than previous calculations based on the scaling model. Combination of the two can explain about a half of the ``GeV Excess'' in the EGRET Galactic diffuse gamma-ray spectrum with the local cosmic proton spectrum (power-law index around 2.7). The excess can be fully explained if the proton spectral index in the Galactic ridge is harder by 0.2 in power-law index. We also found that the diffractive process enhances positrons over electrons and the scaling violation gives 50-100% higher antiproton yield than without the violation, both in the multi-GeV range. For a power-law proton spectrum of index 2, our interaction model predicts the neutrino flux be twice higher than the Feynman scaling model in the 100TeV range.

2416: Radiative Effect on Particle Acceleration via Relativistic Electromagnetic Expansion

Authors: K. Noguchi, E. Liang (Rice Univ.)

One of the unsolved problems in astrophysics is the acceleration of nonthermal high-energy particles. Recently, a new mechanism of relativistic nonthermal particle acceleration, called the Diamagnetic Relativistic Pulse Accelerator(DRPA), discovered using multi-dimensional Particle-in-Cell(PIC) simulations. Here we study the effect of radiation on an electron-positron plasma accelerated by the DRPA, by introducing the radiation force in our 2D PIC code. We find that even with the radiation dumping the DRPA mechanism remains robust and particles are accelerated to over gamma>100. After the simulation reaches the quasi-equilibrium state, kinetic energy becomes constant, and field energy is converted to radiation using particles as the transfer agent. We discuss the angular distribution and polarization of the radiation.

2417: Measurement of Air Fluorescence at 28.5 GeV and in Electromagnetic Showers

Authors: Kevin Reil (SLAC)

Air fluorescence telescopes, such as those employed by the HiRes and Auger experiments, are used to determine the energy deposited as ultra-high energy cosmic rays (UHECR) shower in the atmosphere. The Fluorescence in Air from Showers (FLASH) experiment will improve the calibration of this technique by measuring the yield of ultra-violet light produced per charged particle in air. The 28.5 GeV electron beam of the Final Focus Test Beam (FFTB) facility at SLAC was used to measure the amount of light produced and its spectral distribution. Additionally, an investigation was made to confirm that the fluorescence light produced in an electromagnetic shower follows the predicted shower development. The electron beam was showered through a variety of radiation lengths of alumina (critical energy and effective radiation length similar to air). Preliminary results are presented.

2418: Detection of TeV Gamma-Rays from Extended Sources with Milagro

Authors: Pablo M. Saz Parkinson (University of California, Santa Cruz) for the Milagro Collaboration

The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. A 4800 m^2 pond instrumented with 723 8" PMTs detects Cherenkov light produced by secondary air-shower particles. An array of 175 4000 liter water tanks surrounding the central pond detector was recently added, extending the physical area of the Milagro observatory to 40,000 m^2 and substantially increasing the sensitivity of the detector. Because of its wide field of view and high duty cycle, Milagro is ideal for monitoring the northern sky almost continuously (>90% duty cycle) in the 100 GeV to 100 TeV energy range. Here we discuss the first detection of TeV gamma-rays from the inner Galactic plane region. We also report the detection of an extended TeV source coincident with the EGRET source 3EG J0520+2556, as well as the observation of extended TeV emission from the Cygnus region of the Galactic plane.

2419: TeV Emission from Active Black Holes

Authors: Stefan J. Wagner (Landessternwarte) for the H.E.S.S. Collaboration

We discuss gamma-ray observations of active black holes with the H.E.S.S. Cherenkov array. Being in full operation since early 2004, the H.E.S.S. array has observed several active black holes, mostly together with simultaneous observations in other energy bands. In this presentation we describe the observational results, discuss newly discovered sources, and present variability and spectral data for previously identified and newly detected sources. Due to its improved sensitivity, multifrequency studies studies with improved temporal sampling, better spectral coverage and wider dynamic range. Modelling of the new data results in much improved insight into Blazar emission processes as well as in new constraints on the opacitity of the universe in the TeV energy band.

2501: Recent Results from the High Resolution Fly's Eye Experiment

Authors: Robert Atkins (University of Utah) for the HiRes Collaboration

The High Resolution Fly's Eye group (HiRes) has been operating the HiRes UHECR observatory at the US Army's Dugway Proving Grounds. We will be presenting our most recent results in regards to cosmic-ray anisotropy, spectrum, and the proton-air cross section measurements. These results are based on five years of monocular data and two years of stereo data

2502: Status of the ANTARES Neutrino Telescope

Authors: Paschal Coyle (Centre de Physiques des Particules de Marseille)

ANTARES is a high energy neutrino telescope currently under construction in the Mediterranean Sea near Toulon. The detector design and the expected performances are reported. The results from prototype tests and the current status of the project are described.

2503: Search for Possible Exotic Contributions to Atmospheric Neutrino Oscillations

Authors: G.Giacomelli, V.Popa, M.Sioli (University of Bologna and INFN, Bologna)

Using a set of MACRO data on upward going muons for which an energy measurement was made via multiple Coulomb scattering, a search was made for possible exotic contributions to atmospheric neutrino oscillations coming from Lorentz invariance violation or violation of the equivalence principle. A discussion of the data and limits are presented.

2504: Strong Cosmic Magnetic Fields and Currents in Astrophysics

Authors: Howard D. Greyber

For about 100 years, orthodox belief has been that only gravitational attraction from a positive density fluctuation forms galaxies. However, in my "SMF Induced Galaxy Formation" model, a series of plasma astrophysics processes occurred after "Combination Time" in the Big Bang model which explain both the origin of a very large-scale primordial magnetic field together with the origin of very large-scale structure in the Universe. When all galaxies and quasars formed by gravitational collapse, in the presence of the almost uniform primordial magnetic field, plasma physics shows that an equatorial electric current is generated in each, i.e. a "Storage Ring" or "Gravitationally Bound Current Loop" (GBCL). The presence of a Storage Ring (SR) around the galactic nucleus, presumably a Black Hole, defines the nature of the galactic "Central Engine". When the ratio of magnetic energy to rotational energy is very high, quasars and radio galaxies with strong, very long jets result. But when that ratio is much smaller, what appears more like a disk is formed, and, due to Rayleigh-Taylor instability, usually two spiral arms are formed with magnetic field lines directed in one direction above the plane of the galaxy, and in the opposite direction below the plane. In his thoughtful 1997 article in "Critical Dialogues in Astrophysics", Princeton Univ. Press, Professor. Eugene Parker (UChicago) stresses a very fundamental astrophysics puzzle, concluding that very large-scale magnetic fields in the Universe apparently cannot be explained by present-day physics. In my Ref. 3 below, the very same problem is analyzed and an explanation described that is based on Spinodal Decomposition around Combination Time in the Big Bang Model The SR probably lasts only a few billion years after the gravitational collapse that forms the galaxy/quasar, since once the gravitational collapse ends, all processes tend to force it to decay. Thus no SR is expected in the Local Group made up mostly of very old spiral galaxies like our own Milky Way. Gamma Ray Bursts involve the release of galactic gravitational collapse stored energy. The recent discovery of almost 100% polarization of the prompt gamma ray emission from GRB021206, (1), confirms my 44 year old "Strong" Magnetic Field model (SMF) for galactic dynamics. In SMF, Storage Ring particles were accelerated long ago during the original gravitational collapse of the pregalactic or prequasar plasma cloud that is permeated by an almost uniform primordial magnetic field (2,3,4) The enormous, intense, slender, relativistic, stable, completely coherent Storage Ring stores a small fraction of the huge galactic gravitational collapse energy in an almost radiationless state, unless disturbed. The concept of an Astrophysical Storage Ring was introduced by me in l961. At first it was to explain galactic structure, but soon it proved useful to explain active galactic nuclei (AGN) and the dynamics of quasar/AGN jets (3) In SMF, AGN and galactic morphology and dynamics vary as the ratio of magnetic energy to rotational energy in the particular object. Gamma ray bursts (GRB) are due simply to a "rock". i.e. a white dwarf, ordinary star, neutron star, asteroid, planet, etc. falling rapidly through the Storage Ring and being almost instantly vaporized into a hot plasma fireball, causing an electromagnetic shower (2). Then the fireball speeds into the huge organized magnetic field surrounding the current ring, thus generating very highly polarized prompt gamma ray emission (as seen in GRB021206) from the synchrotron radiation process. Note that the very hot fireball produced by the beam-target interaction speeds on, and is the GRB "Afterglow" that is measured by a great many observers for weeks later The timing fits the GRB observations nicely. For instance, a "rock" racing at 1000 kilometers per second across a 20,000 km. path in the beam would produce a twenty second burst. Other times, a target might track across a short chord for a short burst. Space missions have shown that often typical currents in space plasmas include some slender filaments. Thus the puzzling less than one millisecond spikes observed in some GRB are simply describing the structure of that particular ring current at that particular time.

2505: The Particle Physics Reach of High-Energy Neutrino Astronomy

Authors: Dan Hooper (Oxford University)

A great number of questions in particle physics can be addressed by the new generations of astro-particle physics experiments being developed. I will discuss, in particular, some of the particle physics scenarios which may be probed by next generation high-energy neutrino telescopes including models of low scale quantum gravity, microscopic black hole production, electroweak instanton induced interactions, quantum decoherence, neutrino decay and others.

2506: Gamma Rays from Dark Matter Annihilation in the Galactic Center

Authors: Dieter Horns (Max-Planck-Institut fuer Kernphysik), Agnieszka Jacholkowska (Groupe d'Astroparticules de Montpellier, France)

Recent observations of ground based Cherenkov telescopes have identified a gamma ray signal from within 10~pc of the Galactic center. The signal appears steady and point-like. The possibility of a Dark matter annihilation origin are discussed and conclusions on the required Dark Matter density, halo profile, and Dark matter particle mass are drawn.

2507: Constraining Neutrino Masses by CMB Experiments Alone

Authors: Kazuhide Ichikawa, Masataka Fukugita, Masahiro Kawasaki (Institute for Cosmic Ray Research, University of Tokyo)

It is shown that a subelectronvolt upper limit can be derived on the neutrino mass from the CMB data alone in the Lambda CDM model with the power-law adiabatic perturbations, without the aid of any other cosmological data. Assuming the flatness of the universe, the upper bound we can derive from the current WMAP observations is 2.2 eV at the 95% confidence level for the sum over three species of neutrinos (0.75 eV for each species assuming neutrino mass is degenerate). This constraint may be loosened if we abandon the flatness assumption but only by up to 4% for total Omega =1.02, the WMAP limit on the spatial curvature. We argue that it would be difficult to improve the limit much beyond 1.5 eV using only the CMB data, even if their statistics are substantially improved. However, a significant improvement of the limit is possible if an external input is introduced that constrains the Hubble constant from below. The parameter correlation and the mechanism of CMB perturbations that give rise to the limit on the neutrino mass are also elucidated. [Ref. K. Ichikawa, M. Fukugita, M. Kawasaki, astro-ph/0409768]

2508: Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)

Authors: G. Bogaert (Ecole Polytechnique, France), Y. Fukazawa (Hiroshima University), Y. Saito, T. Takahashi (ISAS, Japan); L. Barbier, P. Bloser, A. Harding, S. Hunter, J. Krizmanic, J. Mitchell, R. Streitmatter (NASA-GSFC), R. Fernholz, E. Groth, D. Marlow (Princeton University), P. Carlson, W. Klamra, M. Pearce (Royal Inst. of Tech. (KTH), Sweden); P. Chen, T. Kamae, V. Andersson, G. Madejski, T. Mizuno, J. Ng, H. Tajima, T. Thurston (SLAC), C.-I. Bjornsson, C. Fransson, S. Larsson, F. Ryde (Stockholm Univ., Sweden), J. Kataoka, N. Kawai (Tokyo Inst. of Tech.), S. Gunji, H. Sakurai, Y. Yamashita (Yamagata University)

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters. Gamma-rays enetering from 5deg FOV will strike a fast scintillator and some will be Compton scattered. A fraction of scattered photons will be absorbed in another fast scintillator (or undergo a second scatter). Two or more clean hits on fast scitillators, compatible with photo-absorption and Compton scattering(s) will be required for a valid event. A prototype instrument has been tested in a polarized soft gamma-ray beam at Advanced Photon Source, confirming predictions on EGS4 and Geant4. Its background rejection capability has also been demonstrated with high rate electrons from Sr90.

2509: X-ray Dissociation Regions in the NGC 6334 Complex

Authors: Sungeun Kim (Sejong University)

Photodissociation by ultraviolet radiation plays an important role in the evolution of high-mass star forming regions, but less is known about the effects of X-ray fluxes on the molecular clouds in these regions. Strong X-ray emission has been detected from the massive star forming complex NGC6334 by the ASCA satellite, giving us the opportunity to examine the effect of X-ray emission on star formation. We present maps of submillimeter emission from NGC6334, in both CI 809 GHz fine structure line of atomic carbon and CO 7-6 rotatonal transition of CO. Comparing these maps to the archival ASCA data, we show that, in the south of NGC6334, the majority of the CI emission can be accounted for by the effects of the X-ray flux on the molecular cloud.

2510: Strong Enhancement of Neutrino Emission in Magnetized Relativistic Jets

Authors: Vl.V. Kocharovsky, E.V. Derishev (Inst. Applied Physics RAS, Russia), V.V. Kocharovsky (Texas A&M University/Inst. Applied Physics RAS)

We consider two-component (protons plus neutrons) relativistic jets in the regime of strong decoupling, when the Lorentz factor of the proton component relative to the neutron component is much greater than unity. In this case, inelastic nucleon- nucleon collisions in the presence of magnetic field give rise to powerful neutrino emission. The latter, according to the solution of hydrodynamical equations with losses, drains the major part of the jet's kinetic energy. One of the most interesting features of the neutrino emission is that the energy of individual neutrinos (in the observer's frame, it is in GeV-TeV range) greatly exceeds the sum of energies of colliding proton and neutron. The phenomenon of enhanced neutrino emission, which is inherent to supercritically-accreting black holes, makes it more difficult to obtain highly relativistic outflows, but on the other hand, increases the neutrino signal to the level which is possible to detect.

2511: Observations of the Shell-Type Supernova Remnants RX J0852.0-4622 (Vela Junior) and RX J1713.7-3946 with H.E.S.S.

Authors: David Berge (Max Planck Institut fur Kernphysik), Nukri Komin (Humboldt-Universitat zu Berlin), Marianne Lemoine-Goumard (Laboratoire Leprince-Ringuet, Ecole Polytechnique), Mathieu de Naurois (Laboratoire de Physique Nucleaire et de Hautes Energies, Universites Paris VI & VII), Gavin Rowell (Max Planck Institut fur Kernphysik)

Shell-type supernova remnants (SNR) are the prime candidates for cosmic ray production. TeV gamma emission from the shells is believed to be the decisive ingredient for unravelling the underlying acceleration mechanisms. We report on the detection of the SNRs RX J0852.0-4622 and RX J1713.7-3946 by H.E.S.S. in observations made in 2003 and 2004. Both sources are found to be clearly extended with morphologies correlated with those from X-ray observations. RX J0852.0-4622 and RX J1713.7-3946 are thus the first SNRs ever resolved in TeV gamma rays. Preliminary results on signal strength, source morphologies and energy spectra are presented.

2512: The On-going CDMS-II Dark Matter Search at the Soudan Mine

Authors: R.W. Ogburn for the CDMS II Collaboration

The Cryogenic Dark Matter Search (CDMS) has recently completed its first year of running in the deep site at the Soudan Underground Laboratory (2090 mwe). This year produced two distinct data sets: the first, Run 118, used the same four germanium and two silicon detectors as previous CDMS data sets from the shallower Stanford site; while the second, Run 119, included two additional Ge detectors and four Si detectors. The Run 118 data set, with 52.7 kg-days of Ge exposure before cuts, currently gives the world's best exclusion limit for spin-independent WIMP interactions: 4 x 10^-43 cm^2 for a WIMP mass of 60 GeV / c^2 (90% confidence level). Run 119 provides 110 kg-days of Ge exposure before cuts. The blinded analysis of this data set is in progress, with an expected improvement in combined sensitivity of a factor of three.

2513: The Dynamics of Charged Particle of Ultra High Energy in CMB

Authors: Viktor Musakhanyan (Yerevan State Medical University)

The dynamics of charged particle of ultra high-energy moving in the Cosmic Microwave Background (CMB) is considered. Since the parameters for CMB, 1) the intensity and 2) the ratio of quantum’s energy to the energy of charged particle are small, we handle the problem within the frameworks of Classical Electrodynamics. Solution of relativistic equation of motion results, after averaging over random phases of the waves, in a small additional acceleration, hence the well-known GZK cut-off for charged Ultra High Energy Cosmic Rays (UHECR) becomes controversial. Owing to the relativistic invariance of the wave’s phase, the huge increase of frequency both in the rest and in the center of mass reference frames of the ultra high-energy charged particle results in the corresponding decrease of the length of interaction. Therefore, the obtained energy gain is independent of chosen reference frames. Thus, there is no theoretical constrains for UHECR originated in far Universe during their long journey to Earth. Spectrum of UHECR is discussed and both the knee and the ankle are considered.

2514: The Status of XENON Dark Matter Project

Authors: Elena Aprile, Karl-Ludwig Giboni, Pawel Majewski, Kaixuan Ni, Bhartendu Singh, Masaki Yamashita(Columbia University), Richard Gaitskell, Peter Sorensen, Luiz de Viveiros(Brown University), Uwe Oberlack (Rice University), Tom Shutt, John Kwong (Princeton University), Laura Baudis (University of Florida), Daniel McKinsey, Richard Hasty, Angel Manzur(Yale University), Chris Hagmann, Adam Bernstein, Celeste Winant(LLNL)

Liquid xenon detector is one of the most promising technologies to produce unambiguous signals from dark matter, by directly detecting WIMPs (Weakly Interacting Massive Particles) via their elastic scattering off Xe nuclei. The XENON experiment with a fiducial mass of 1 tonne liquid xenon (XENON1T), distributed in 10 independent detectors (XENON100), will be able to probe the lowest WIMP interaction cross sections predicted by various SUSY models. The key idea is to use 3-D position sensitive dual-phase (liquid/gas) xenon time projection chambers (TPCs) to discriminate, event by event, between nuclear recoils from WIMPs or neutrons, and electron recoils from background, down to at least a 16 keV recoil energy level. We will first illustrate our technology in details. Then we will present the results from the XENON R&D phase, and current status and the most recent progress towards a prototype with 10kg fiducial mass (XENON10), which will be deployed in an underground lab in 2005. We will also discuss the expected signature and physics results from XENON10 from detailed simulations.

2515: Accelerator Measurements of the Askaryan effect in Rock Salt: Towards Teraton Underground Neutrino Detectors

Authors: Radovan Milincic (University of Hawaii)

We report on accelerator measurements of the Askaryan effect--coherent radio emission from charge asymmetry in electromagnetic cascades--using synthetic rock salt as the dielectric medium for cascades produced by GeV bremsstrahlung photons provided by the Stanford Linear Accelerator. Our goal was to extend our prior discovery measurements to a wider range of parameter space and explore the effect in a dielectric medium of great potential interest to large scale ultra-high energy neutrino detectors: rock salt, which occurs naturally in high purity formations containing in many cases hundreds of km^3 of water-equivalent mass. We observed strong coherent pulsed radio emission over a frequency band from 0.2-15 GHz, confirming that the predicted effect obtains for this medium. A grid of embedded dual-polarization antennas was used to confirm the high degree of linear polarization and track the change of direction of the electric-field vector with azimuth around the shower. Coherence was observed over 4 orders of magnitude of shower energy. The frequency dependence of the radiation was tested over two orders of magnitude of UHF and microwave frequencies.

2516: Tuning in to UHE Neutrinos in Antarctica - The ANITA Experiment

Authors: Predrag Miocinovic (University of Hawaii), for ANITA Collaboration

The Antarctic Impulsive Transient Antenna (ANITA) experiment is being developed to search for very-high-energy neutrino interactions in the Antarctic ice cap. A neutrino interaction in the ice will produce a radio pulse by the means of Askaryan effect. The large radio transparency of ice allows for such a pulse to be recorded by a cluster of balloon-borne antennas. The details of the ANITA instrument, now in a construction phase, and the exciting science we hope to achieve will be discussed. In order to prepare for the main mission (planned for Dec. 2006), we have flown ANITA-lite during the 2003/04 austral seasoon. ANITA-lite consisted of two quadridge horn antennas and a prototype RF triggering and recording system. Here we present the results of impulsive RF background survey of Antarctica, as well as proof-of-principle gain, tracking, and timing calibrations conducted by observing solar radio emissions and calibration radio-pulses. The preliminary UHE neutrino flux limits based on ANITA-lite data will also be presented.

2517: The CERN Solar Axion Telescope CAST: Status and First Results

Authors: M. Kuster (Max-Planck-Institut fuer Extraterrestrische Physik) on behalf of the CAST collaboration

The axion is a pseudo scalar particle and with the neutralino the leading dark matter candidate. The axion was predicted by Peccei and Quinn in 1977 to solve the strong CP problem. If the Peccei-Quinn-Mechanism is realized in nature, axions can be produced in the inner most core of the sun by Primakoff effect. Thereby, thermally distributed photons which typically have an energy of several keV are scattered from the electromagnetic field of charged nuclei in the plasma in the solar interior and converted to axions. The physical principle of the CAST experiment is based on the inverse process using a 9 T, 9.26 m long magnetic field of a superconducting LHC prototype magnet to reconvert the axions to X-rays on Earth. Due to the strong magnetic field and the length of the conversion volume the detection limit of the experiment is largely improved compared to earlier experiments and for the first time reaches the limits predicted by theoretical-astrophysical models. We will give a general overview on axions, the CAST experiment, and will present first results from data acquired in 2003 and 2004.

2518: HAWC: A Next Generation All-Sky VHE Gamma-Ray Telescope

Authors: Gus Sinnis (LANL), Andrew Smith (University of Maryland), Julie McEnery (NASA Goddard), James T. Linnemann (Michigan State University)

The study of the universe at energies above 100 GeV is a relatively new and exciting field. The current generation of pointed instruments has detected TeV gamma rays from at least 10 sources and the next generation of detectors promises a large increase in sensitivity. We have also seen the development of a new type of all-sky monitor in this energy regime based on water Cherenkov technology (Milagro). To fully understand the universe at these extreme energies requires a highly sensitive detector capable of continuously monitoring the entire overhead sky. Such an instrument could observe prompt emission from gamma-ray bursts and probe the limits of Lorentz invariance at high energies. With sufficient sensitivity it could detect short transients (~15 minutes) from active galaxies and study the time structure of flares at energies unattainable to space-based instruments. Unlike pointed instruments, a wide-field instrument can make an unbiased study of all active galaxies and enable many multi-wavelength campaigns to study these objects. This contribution describes the current understanding of the design and performance of a next generation water Cherenkov detector. To attain a low energy threshold and high sensitivity, the detector should be located at high altitude (> 4km) and have a large area (~40,000 m^2). Such an instrument could detect gamma ray bursts out to a redshift of 1, observe flares from active galaxies as short as 15 minutes in duration, and survey the overhead sky at a level of <50 mCrab in one year.

2519: Search for Dark Matter with GLAST

Authors: Aldo Morselli (INFN Roma2)

The direct detection of annihilation products in cosmic rays offers an alternative way to search for supersymmetric dark matter particles candidates. The study of the spectrum of gamma-rays and positrons in space has already showed some deviation from the expected signals but with weak statistical evidence. We will review the present situation and the achievable limits with the experiments GLAST, AMS and PAMELA.

2520: High-Energy Neutrinos Produced by Interactions of Relativistic Protons in Shocked Pulsar Winds

Authors: Shigehiro Nagataki (Yukawa Institute for Theoretical Physics, Kyoto University)

We have estimated fluxes of neutrinos and gamma rays that are generated from the decay of charged and neutral pions from a pulsar surrounded by supernova ejecta in our Galaxy, including effects of interactions between high-energy cosmic rays themselves in the nebula flow, assuming that hadronic components are the energetically dominant species in the pulsar wind. We have found that fluxes of neutrinos and gamma rays depend very sensitively on the wind luminosity, which is assumed to be comparable to the spin-down luminosity. In the case where B=10^12 G and P=1 ms, neutrinos should be detected by km^3 high-energy neutrino detectors such as AMANDA and IceCube. Also, gamma rays should be detected by Cerenkov telescopes such as CANGAROO and HESS, as well as by gamma-ray satellites such as GLAST.

2521: Particle Acceleration Efficiencies in Astrophysical Shear Flows

Authors: Frank M. Rieger, Peter Duffy (National University of Ireland)

The acceleration of energetic particles in astrophysical shear flows is analyzed. We show that in the presence of a non-relativistic gradual velocity shear, power law particle momentum distributions may be generated, assuming a momentum-dependent scattering time. We consider possible acceleration sites in astrophysical jets and study the conditions for efficient acceleration. It is shown, for example, that in the presence of a gradual shear flow and a gyro-dependent particle mean free path, synchrotron radiation losses are longer be able to stop the acceleration once it has started to work efficiently. This suggests that shear acceleration may naturally account for a second, non-thermal population of energetic particles in addition to a shock-accelerated one. The possible relevance of shear acceleration is shortly discussed with reference to the relativistic jet in the quasar 3C~273.

2522: The Gamma-ray Large Area Space Telescope (GLAST) Mission

Authors: Peter Michelson (Stanford), Charles Meegan (NASA Marshall Space Flight Center), J. Grindlay (Harvard), S. Ritz (NASA Goddard Space Flight Center) on behalf of the GLAST Mission Team

The Gamma-ray Large Area Space Telescope, GLAST, is a mission under construction to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of high energy phenomena, including black holes and active galactic nuclei; gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations, Lorentz invariance violation, and exotic relics from the Big Bang. In addition to the science opportunities, this poster will include a description of the instruments, the opportunities for guest observers, and the mission status.

2523: COUPP: Searching for WIMP Dark Matter with a New Kind of Bubble Chamber

Authors: J.I Collar, J. Hall, D. Nakazawa, K. O'Sullivan, A. Raskin (University of Chicago), A. Sonnenschein (University of Chicago/KIPAC), M. Crisler, D. Holmgren, R. Plunkett, E. Ramberg (Fermilab)

The Chicago Observatory for Underground Particle Physics (COUPP) will be an experiment to search for Weakly Interacting Massive Particles (WIMPs), based a new type of bubble chamber. Improvements in bubble chamber technology now allow the construction of detectors that are nearly continuously sensitive to WIMP-nucleus scattering, while remaining insensitive to backgrounds from environmental beta and gamma radiation. The scalability and favorable enconomics of this technology may allow WIMP searches with sensitivity improved by several orders of magnitude over the current generation experiments, such as CDMS-II. We will discuss the first measurements made with a 1 liter chamber and prospects for the future.

2524: Micro-Channel Plate (MCP) Detector for Liquid Xenon Dark Matter Search

Authors: Richard Gaitskell, Peter Sorensen (Brown University)

We have tested the response of a Micro-Channel Plate (MCP) to liquid xenon (LXe) scintillation light, for use in next-generation LXe Dark Matter direct-detection experiments. This is the first report of such a device operating immersed in LXe. We compare response to Xe electron recoils (gamma events) and nuclear recoils (neutron events). The MCP has inherently faster time resolution than a PMT, which provides greater sensitivity to pulse shape for low-energy (few tens of keV) events. This is exploited for Pulse-Shape Discrimination (PSD) of nuclear v. electron recoils. Other features of the MCP which are attractive for LXe Dark Matter direct-detection experiments include a segmented anode and compact, square geometry. The former is shown to yield position resolution of ~ 10mm. We also present preliminary results of dual-phase operation, in which ionization electrons (from gamma and neutron interactions) are extracted through the liquid-gas interface under external E-field, and causes electroluminesence in the gas phase. This additional signal provides a powerful discrimination technique against background events. It is also adversely affected by impurities in the LXe; we assess the impact of the MCP in this regard.

2525: Design and Performance of Soft Gamma-ray Detector for NeXT Mission

Authors: H. Tajima, T. Kamae, G. Madejski (KIPAC/SLAC) T. Mitani, K. Nakazawa, T. Tanaka, T. Takahashi, S. Watanabe (ISAS/JAXA), Y. Fukazawa (Hiroshima University), M. Kokubun, K. Makishima (University of Tokyo), Y. Terada (RIKEN), M. Nomachi (Osaka University), J. Kataoka (Tokyo Institute of Technology), M. Tashiro (Saitama University) and the NeXT/SGD team

The Soft Gamma-ray Detector (SGD) on board NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view (FOV), which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and CdTe detectors. It can detect photons in a wide energy band (0.05-1 MeV) at a background level of 10^-7 counts/s/cm^2/keV; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD, allowing to achieve both high angular resolution and good background rejection capability. It is worthwhile mentioning an additional capability of the SGD, its ability to measure gamma-ray polarization, which opens up a new window to study properties of astronomical objects. We will present the development of key technologies to realize the SGD; high quality CdTe, low noise front-end ASIC and bump bonding tecnology. The energy resolution of 1.6 keV (FWHM) for CdTe pixel detectors and 1.2 keV for Si strip detectors have been measured. We also present the validation of EGS4 MC simulation used to evaluate the perfromance of the SGD.

2526: Stochastic Particle Acceleration in Relativistic Parallel Shocks

Authors: Joni J.P. Virtanen (Tuorla Observatory), Rami Vainio (University of Helsinki)

We present results of test-particle simulations on both the first and the second order Fermi acceleration for relativistic parallel shock waves. Our studies suggest that the role of the second order mechanism in the turbulent downstream of a relativistic shock with respect to the first order mechanism at the shock front may have been underestimated in the past, and that the second order mechanism may have significant effects on the form of the particle spectra and its time evolution.

2527: Cosmic Ray Transport in MHD Turbulence

Authors: Huirong Yan, A. Lazarian (University of Wisconsin, Madison)

Recent advances in understanding of magnetohydrodynamic (MHD) turbulence call for revisions in the picture of cosmic ray transport. We use recently obtained scaling laws for MHD modes to obtain the scattering frequency for cosmic rays. Adopting recently obtained scaling laws for MHD modes, we studied CR transport and acceleration for various astrophysical environments with realistic interstellar turbulence driving. We found that dynamics of turbulence must be taken into account when considering transit time damping even for high energy CRs. We show that fast modes provide the dominant contribution to cosmic ray scattering for the typical interstellar conditions in spite of the fact that fast modes are subjected to damping. We determine how the efficiency of the scattering depends on the characteristics of ionized media, e.g. plasma beta. In addition, we found that the traditional picture of shock acceleration is incomplete, as it ignores the effect of preexisting turbulence in the surrounding gas. Our research revealed suppression of streaming instability, which is an essential component of first order Fermi acceleration in shocks, by the ambient MHD turbulence. This suppression limits the energy of cosmic rays that can be accelerated by supernovae and invalidates many conclusions reached on cosmic ray confinement for models of galaxies embedded in fully ionized plasma.

2528: Recent Results from the ADMX Dark Matter Axion Search

Authors: Daniel B. Yu (LLNL) for the ADMX Collaboration

We report results from an experiment to search for axions, a hypothetical elementary particle and cold dark matter candidate. In this experiment, halo axions entering a resonant RF cavity immersed in a static magnetic field convert into microwave photons, with the resulting photons detected by a low-noise receiver. We present new limits on the axion-to-photon coupling and local axion dark matter halo mass density in the axion mass range 1.9--2.3 micro eV, broadening the search range to 1.9--3.3 micro eV. This is the mass where dark matter axions are expected. In addition, we report first results from an improved analysis technique, which enhances the experiment sensitivity by 13 %.

2529: Beyond the CDMS-II Dark Matter search: SuperCDMS

Authors: Paul L. Brink (Stanford University) for the CDMS II collaboration

Presently the CDMS II collaboration's Weakly Interacting Massive Particle (WIMP) search at the Soudan Underground Laboratory sets the most stringent exclusion limits of any Cold Dark Matter direct-detection experiment. To extend our reach further, and thus probe supersymmetry models also of interest at the LHC, we propose SuperCDMS that would take advantage of a new deeper site at the recently approved SNOLab facility in Canada. To utilize the full potential of this new site the first part of the SuperCDMS program, a 'Development Phase' proposal recently submitted to NSF & DOE, will develop new larger, higher performance, and more radioactively clean detectors of a similar technology developed at Stanford for CDMS II. The later SuperCDMS Phase A and Phase B proposals will outline our plans to deploy 27 kg, and later 145 kg-worth of Ge detectors.

2530: Relativistic Collisionless Shocks: Shock Structure and Particle Acceleration

Authors: Anatoly Spitkovsky (KIPAC, Stanford University)

I discuss the 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization ("sigma" parameter). I will demonstrate how the structure of the shock varies as a function of sigma for both perpendicular and oblique shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. I demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). I further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this poses a restriction on the structure and composition of gamma-ray bursts and pulsar wind outflows.

2531: CDMS-II: Spin-dependent limits

Authors: Jeffrey Filippini (UC Berkeley) for the CDMS Collaboration

The first data set from the CDMS II experiment represents 52.7 raw kg-days of data, taken at a depth of 2090 mwe at the Soudan Underground Laboratory. The analysis of these data has produced the strongest limits to date on spin-independent WIMP-nucleon interactions. In addition, CDMS possesses substantial sensitivity to spin-dependent WIMP-nucleon interactions – in particular, to WIMP-neutron couplings. We have carried out a spin-dependent analysis of our recent data set, yielding limits competitive with those of other major experiments: 1.5x10^-37 cm^2 for WIMP-neutron couplings of a 60 GeV/c^2 WIMP, 1.0x10^-35 cm^2 for WIMP-proton couplings of such a WIMP. When combined with a previous data set taken at a shallow site, we exclude an interpretation of the DAMA signal region in terms of pure spin-dependent WIMP-neutron coupling (within the standard halo model). The additional data expected from our 2004 and 2005 runs should further extend our reach by a factor of ~20.