http://www.kitp.ucsb.edu/online/grb_c06/ KITP Conference: Supernova and Gamma-Ray Burst Remnants KITP Conference: Supernova and Gamma-Ray Burst Remnants en-us © 2006 by the individual authors doug@kitp.ucsb.edu webmaster@kitp.ucsb.edu Thu, 16 Mar 2006 14:21:41 -0800 Thu, 16 Mar 2006 14:21:41 -0800 Education http://blogs.law.harvard.edu/tech/rss 240 http://online.kitp.ucsb.edu/online/grb_c06/aharonian/ Felix Aharonian (MPI, Heidelberg) (Felix Aharonian (MPI, Heidelberg)) Felix Aharonian (MPI, Heidelberg) Felix Aharonian (MPI, Heidelberg) Felix Aharonian (MPI, Heidelberg) (Thu, 09 Feb 2006 09:00) I will review the recent observations of multi-TeV gamma-rays from young shell type supernova remnants, and argue that TeV gamma ray emission is produced through interactions of protons accelerated in the shell up toenergies $E \geq$ 100 TeV. I also will discus the high energy signatures, as well as possible observational strategies for the search for GalacticPeVatrons. http://online.kitp.ucsb.edu/online/grb_c06/aharonian/ Thu, 09 Feb 2006 09:00:00 -0800 39:07 http://online.kitp.ucsb.edu/online/grb_c06/allen/ Glenn Allen (MIT) (Glenn Allen (MIT)) Glenn Allen (MIT) Glenn Allen (MIT) Glenn Allen (MIT) (Fri, 10 Feb 2006 14:20) G. E. Allen (MIT), M. D. Stage (UMass), J. C. Houck (MIT) and J. E. Davis (MIT)We present the results of spectroscopic analyses of 1.1 megaseconds of Chandra ACIS X-ray data for the supernova remnant Cas A. The analyses were performed by extracting spectra from 1\"x1\" to 7\"x7\" overlapping boxes at each point on a rectangular grid with 1\" spacing. Each set of spectra and spatially-dependent responses was fitted with a simple thermal model. The results of this analysis suggest that some, if not all, of the regions in which the X-ray synchrotron emission is produced can be identified. These regions have relatively high fitted electron temperatures and relatively low elemental abundances. The regions whose X-ray emission is dominated by synchrotron radiation seem be distributed around the forward shock, except, perhaps, for portions of the southwestern face of the remnant. The data for these regions were subsequently fitted with a synchrotron emission model. The fitted critical frequencies associated with the highest-energy electrons vary from about 10^16-10^18 Hz. This variation indicates that the cut-off energy of the electron spectrum varies by as much as one order of magnitude and/or the magnetic field strength varies by as much as two orders of magnitude. In the regions with the highest critical frequencies, the electrons must be accelerated about as fast as possible (i.e. have diffusion coefficients comparable to the Bohm coefficient). http://online.kitp.ucsb.edu/online/grb_c06/allen/ Fri, 10 Feb 2006 14:20:00 -0800 33:08 http://online.kitp.ucsb.edu/online/grb_c06/badenes/ Carlos Badenes (Rutgers) (Carlos Badenes (Rutgers)) Carlos Badenes (Rutgers) Carlos Badenes (Rutgers) Carlos Badenes (Rutgers) (Fri, 10 Feb 2006 10:50) Thanks to Chandra and XMM-Newton, spatially resolved spectroscopy of SNRs in the X-ray band has become a reality. Several impressive data sets for ejecta-dominated SNRs can now be found in the archives, the Cas A VLP just being one (albeit probably the most spectacular) example. However, it is often hard to establish quantitative, unambiguous connections between the X-ray observations of SNRs and the dramatic events involved in a core collapse or thermonuclear SN explosion. The reason for this is that the very high quality of the data sets generated by Chandra and XMM for the likes of Cas A, SNR 292.0+1.8, Tycho, and SN 1006 has surpassed our ability to analyze them. The core of the problem is in the transient nature of the plasmas in SNRs, which results in anintimate relationship between the structure of the ejecta and AM, the SNR dynamics arising from their interaction, and the ensuing X-ray emission. Thus, the ONLY way to understand the X-ray observations of ejecta-dominated SNRs at all levels, from the spatially integrated spectra to the subarcsecond scales that can be resolved by Chandra, is to couple hydrodynamic simulations to nonequilibrium ionization (NEI) calculations and X-ray spectral codes. I will review the basic ingredients that enter this kind of calculations, and what are the prospects for using them to understand the X-ray emission from the shocked ejecta in young SNRs. This understanding (when it is possible), can turn SNRs into veritable time machines, revealing the secrets of the titanic explosions that generated them hundreds of years ago. http://online.kitp.ucsb.edu/online/grb_c06/badenes/ Fri, 10 Feb 2006 10:50:00 -0800 33:27 http://online.kitp.ucsb.edu/online/grb_c06/baring/ Matthew Baring (Rice Univ.) (Matthew Baring (Rice Univ.)) Matthew Baring (Rice Univ.) Matthew Baring (Rice Univ.) Matthew Baring (Rice Univ.) (Thu, 09 Feb 2006 12:10) The principal paradigm for gamma-ray bursts (GRBs) suggests that the prompt transient gamma-ray signal arises from multiple shocks internal to the relativistic expansion. Since this signal is most probably electromagnetic in origin, a major issue concerns how the electrons get energized and accelerated in burst environments. This paper explores this issue of electron heating/acceleration at relativistic shocks that pertain to GRB models. Spectral fits to BATSE/EGRET burst data indicate that the preponderance of electrons that are responsible for the prompt emission reside in an intrinsically non-thermal population. Thisdiffers markedly from typical populations generated in acceleration simulations; potential resolutions of this conflict such as the action of self-absorption are discussed. In addition, the spectral analysissuggests that the synchrotron mechanism is favored over synchrotron self-Compton scenarios due to the latter$apos;s characteristically broad curvature near the spectral \"peak.\" The merits of other emission processes are also touched upon. A connection of this data interpretation to heating in the shock layer is then made. Expectations for heating of electrons from cross shock electrostatic potentials are presented, exploring the capability of relativistic shocks to generate predominantly non-thermal electron distributions from thermal poolsupstream. Constraints that the EGRET power-law indices provide on the shock parameters will also be discussed. http://online.kitp.ucsb.edu/online/grb_c06/baring/ Thu, 09 Feb 2006 12:10:00 -0800 38:20 http://online.kitp.ucsb.edu/online/grb_c06/blondin/ John Blondin (North Carolina) (John Blondin (North Carolina)) John Blondin (North Carolina) John Blondin (North Carolina) John Blondin (North Carolina) (Tue, 07 Feb 2006 09:00) The origin of asymmetry in core-collapse supernovae may arise in the first few hundred milliseconds after bounce when the nascent shockwave is susceptible to the spherical accretion shock instability. We provide quantitative measurement of the growth of both an axisymmetric mode (l=1) and a non-axisymmetric mode (m=1) in the linear regime, and argue that this instability is a growing pressure wave driven by the dynamic response of the accretion shock. Recent 3D simulations haveshown that the non-axisymmetric mode of the SASI dominates the nonlinear evolution, and can impart a significant amount of angular momentum to the underlying neutron star. http://online.kitp.ucsb.edu/online/grb_c06/blondin/ Tue, 07 Feb 2006 09:00:00 -0800 35:23 http://online.kitp.ucsb.edu/online/grb_c06/burrows/ David Burrows (Penn State) (David Burrows (Penn State)) David Burrows (Penn State) David Burrows (Penn State) David Burrows (Penn State) (Tue, 07 Feb 2006 14:20) NASA's Swift Gamma-Ray Burst Explorer is designed to localize and study Gamma-Ray Bursts (GRBs) and their afterglows, beginning within a few minutes of the burst events. Swift has now discovered over 100 GRBs and has produced detailed X-ray light curves and spectroscopy on over 90% of these, exceeding in the first nine months the total sample of GRB afterglows found in the previous 8 years. Key findings to date include rapid decays at early times and giant X-ray flares, suggesting that the central engines of GRBs continue long past the end of the prompt gamma-ray emission. We have also localized several short GRBs, providing important supporting evidence for compact merger theories for short bursts, but yielding puzzling afterglows with flares that suggest somewhat complex merger processes. I will discuss what these observations may be telling us about black hole creation associated with GRBs. http://online.kitp.ucsb.edu/online/grb_c06/burrows/ Tue, 07 Feb 2006 14:20:00 -0800 38:36 http://online.kitp.ucsb.edu/online/grb_c06/burrows1/ Adam Burrows (Univ. of Arizona) (Adam Burrows (Univ. of Arizona)) Adam Burrows (Univ. of Arizona) Adam Burrows (Univ. of Arizona) Adam Burrows (Univ. of Arizona) (Fri, 10 Feb 2006 09:00) We present a new mechanism for core-collapse supernova explosions that relies upon acoustic power generated in the inner core as the driver. If, and in the circumstances in which, the neutrino mechanism does not obtain, this acoustic mechanism would come into its own. In our simulations, a strong advective-acoustic oscillation a la Foglizzo with a period of ~25-30 milliseconds (ms) arises ~200 ms after bounce. Its growth saturates due to the generation of secondary shocks, and kinks in the resulting shock structure funnel and regulate subsequent accretion onto the inner core. However, this instability is not the primary agent of explosion. Rather, it is the acoustic power generated in the inner turbulent region and most importantly by the excitation and sonic damping of core g-mode oscillations. An l=1 mode with a period of ~3 ms grows to be prominent around ~500 ms after bounce. The accreting protoneutron star is a self-excited oscillator. The associated acoustic power seen in our 11-solar-mass simulation is sufficient to drive the explosion. The angular distribution of the emitted sound is fundamentally aspherical, and the resulting blast is almost unipolar. The sound pulses radiated from the core steepen into shock waves that merge as they propagate into the outer mantle and deposit their energy and momentum with high efficiency. The core oscillation acts like a transducer to convert accretion energy into sound. An advantage of the acoustic mechanism is that acoustic power does not abate until accretion subsides, so that it is available as long as it may be needed to explode the star, unless a black hole is formed. The consequences of this new mechanism for the explosion morphology, the r-process, pulsar kicks, and the systematics with progentior mass and rotation will be explored. http://online.kitp.ucsb.edu/online/grb_c06/burrows1/ Fri, 10 Feb 2006 09:00:00 -0800 41:44 http://online.kitp.ucsb.edu/online/grb_c06/chapman/ Sandra Chapman (Univ. of Warwick) (Sandra Chapman (Univ. of Warwick)) Sandra Chapman (Univ. of Warwick) Sandra Chapman (Univ. of Warwick) Sandra Chapman (Univ. of Warwick) (Thu, 09 Feb 2006 15:00) Recent kinetic simulations of supercritical, quasi-perpendicular shocks yield time varying shock solutions that cyclically reform on the spatio-temporal scales of the incoming protons. Whether a shock solution is stationary or reforming depends upon the plasma parameters which, for SNR shocks are ill defined but believed to be within thetime-dependent regime. We will first review the structure and evolution of the time dependentsolutions, and the acceleration processes of the ions and electrons in these time dependent fields, for a proton-electron plasma. We will then present recent results for a three component plasma: background protons; electrons; and a second heavier ion population. These acceleration mechanisms may generate a suprathermal\"injection$quot; population - a seed population for subsequent acceleration at the shock, which can in turn generate particles at cosmic ray energies. http://online.kitp.ucsb.edu/online/grb_c06/chapman/ Thu, 09 Feb 2006 15:00:00 -0800 30:27 http://online.kitp.ucsb.edu/online/grb_c06/chevalier/ Roger Chevalier (UVA) (Roger Chevalier (UVA)) Roger Chevalier (UVA) Roger Chevalier (UVA) Roger Chevalier (UVA) (Wed, 08 Feb 2006 09:40) The environment of core collapse supernovae is probed by their radio and X-ray emission. The various supernova types (IIP, IIL, IIb, IIn, Ib/c) have characteristic radio properties; the differences can be attributed to the mass loss density and the velocity of the interaction region. The Type Ic SN 1998bw, associated with GRB 980425, fits into this scheme, although with a high velocity. The afterglows of long GRBs are more difficult to reconcile with the expected mass loss environment. http://online.kitp.ucsb.edu/online/grb_c06/chevalier/ Wed, 08 Feb 2006 09:40:00 -0800 38:17 http://online.kitp.ucsb.edu/online/grb_c06/delaney/ Tracey Delaney (Harvard-Smithsonian CfA) (Tracey Delaney (Harvard-Smithsonian CfA)) Tracey Delaney (Harvard-Smithsonian CfA) Tracey Delaney (Harvard-Smithsonian CfA) Tracey Delaney (Harvard-Smithsonian CfA) (Fri, 10 Feb 2006 12:10) I will present an overview of some of the exciting results from Spitzer observations of the young supernova remnant Cassiopeia A. The images from the MIPS instrument at 24 and 70 microns are dominated by thermal emission from dust within the remnant and clearly show the counterjet extending in the opposite direction from the well-known North-East jet. One of the most surprising results from the 24 micron observations is the presence of infrared light echoes in the vicinity of Cas A. These are thought to result from interstellar dust heated by the explosion and by flares from the compact central object. Images taken in the four IRAC bands show the presence of synchrotron emission. The spectral indices measured between 6 cm and IRAC channel 1 at 3.6 micron are flatter than those measured between 6 cm and 20 cm indicating a curved synchrotron spectrum consistent with cosmic-ray-modified shocks. We have also used the IRS instrument in mapping mode to obtainlow-resolution spectra over nearly the entire extent of Cas A. This is the largest single spectral map yet constructed with Spitzer. The spectra, in conjunction with the IRAC images, show that different dust components are associated with different ejecta/circumstellar media components of the remnant. The distribution and composition of the inhomogeneous ejecta and the associated dust indicate that in each direction different nucleosynthetic layers have reached the reverse shock. We have identified diffuse Si and S emission near the center of the remnant that matches the morphology of the absorption seen in the radio at 74 MHz. This material is thought to be ejecta that has not yet encountered the reverse shock but has been photoionized by X-ray and ultraviolet radiation from the remnant. We are able to identify [Ni II] in the remnant. Since the half-life of 56Ni is only 6 days, this material may not be the remains of the Ni synthesized in the supernova explosion. Finally, we have identified strong Ne emission from isolated regions on the northern and southern bright ring. The Ne emission to the south is red-shifted and has no bright optical or X-ray counterpart while the Ne emission to the north forms a blue-shifted ring structure coincident with optical and X-ray oxygen emission. The line connecting these \"caps\" passes within a few arcseconds of the center of the remnant, is roughly oriented along the inferred kick direction of the central compact object, and is approximately at a right angle to the jet direction, perhaps suggesting a bi-directional outflow of Ne-rich ejecta. http://online.kitp.ucsb.edu/online/grb_c06/delaney/ Fri, 10 Feb 2006 12:10:00 -0800 43:04 http://online.kitp.ucsb.edu/online/grb_c06/dermer/ Charles Dermer (NRL) (Charles Dermer (NRL)) Charles Dermer (NRL) Charles Dermer (NRL) Charles Dermer (NRL) (Thu, 09 Feb 2006 09:00) We describe leptonic and hadronic processes in GRB blast waves that lead to the production of multi-MeV photons. Gamma rays emitted by leptons are likely to be synchrotron self-Compton emission, though external Compton photons could be important in some cases. Cascades associated with photohadronic processes are probably the most important source of hadronic gamma rays. Cosmic-ray production by GRBs could explain the origin of high-energy cosmic rays. High-energy neutrinos would be the most clearcut prediction of this scenario, though gamma rays associated with hadronic processes would have distinct signatures compared to those emitted by leptons. http://online.kitp.ucsb.edu/online/grb_c06/dermer/ Thu, 09 Feb 2006 09:00:00 -0800 36:24 http://online.kitp.ucsb.edu/online/grb_c06/dwarkadas/ Vikram Dwarkadas (Univ. of Chicago) (Vikram Dwarkadas (Univ. of Chicago)) Vikram Dwarkadas (Univ. of Chicago) Vikram Dwarkadas (Univ. of Chicago) Vikram Dwarkadas (Univ. of Chicago) (Tue, 07 Feb 2006 14:20) I discuss the formation and growth of the medium around massive stars, especially Wolf-Rayet stars, and its impact on the evolution of the resultant shock wave when the star ends its life as a SN. The circumstellar medium is formed by mass-loss from the star during its various evolutionary stages. Using analytical calculations and numerical simulations, I study the evolution of this medium, multidimensional effects such as hydrodynamical instabilities, and the onset of turbulence. When the star explodes as a SN, the resulting shock wave will interact with this medium. I further explore the impact of the ambient medium on the expansion of the shock wave and the evolution of the remnant. Similarly, the impact on GRB afterglows and absorption spectra of GRBs is considered. http://online.kitp.ucsb.edu/online/grb_c06/dwarkadas/ Tue, 07 Feb 2006 14:20:00 -0800 25:48 http://online.kitp.ucsb.edu/online/grb_c06/einhorn/ Martin Einhorn (KITP Deputy Director) (Martin Einhorn (KITP Deputy Director)) Martin Einhorn (KITP Deputy Director) http://online.kitp.ucsb.edu/online/grb_c06/einhorn/ Mon, 06 Feb 2006 09:00:00 -0800 03:59 http://online.kitp.ucsb.edu/online/grb_c06/ellison/ Donald Ellison (North Carolina) (Donald Ellison (North Carolina)) Donald Ellison (North Carolina) Donald Ellison (North Carolina) Donald Ellison (North Carolina) (Thu, 09 Feb 2006 16:50) The theory of diffusive shock acceleration (DSA) operating in strong, nonrelativistic shocks, clearly allows for the mechanism to be highly efficient. However, it is still an open question if actual collisionless shocks, such as those in young supernova remnants (SNRs), are as efficient as predicted. Fortunately, the nonlinear feedback effects resulting from efficient DSA should produce observable consequences including changes in the morphology of the remnant and a strongly amplified magnetic field. I will outline the theory for nonlinear DSA and apply it to recent observations of young SNRs. Preliminary work on magnetic field amplification will also be presented. This work, which employs a well-tested Monte Carlo simulation, will self-consistently determine the plasma flow, magnetic field, and particle spectrum. Amplified magnetic fields may result in large increases in the maximum particle energy produced in a given shock. http://online.kitp.ucsb.edu/online/grb_c06/ellison/ Thu, 09 Feb 2006 16:50:00 -0800 38:56 http://online.kitp.ucsb.edu/online/grb_c06/fesen/ Robert Fesen (Dartmouth) (Robert Fesen (Dartmouth)) Robert Fesen (Dartmouth) Robert Fesen (Dartmouth) Robert Fesen (Dartmouth) (Mon, 06 Feb 2006 14:20) I will discuss observational evidence suggesting the presence of high-velocity ejecta in the for of opposing jets in likely remnants of core-collapse SNe. I will concentrate on the bright radio and X-ray source Cassiopeia A (Cas A), the youngest known supernova remnant in the Milky Way, which shows optical jets of S-rich ejecta moving at10,000 - 15,000 km/s. While these jets are best seen in optical HST images, they are coincident with extended emission observed in both the X-rays and infrared. http://online.kitp.ucsb.edu/online/grb_c06/fesen/ Mon, 06 Feb 2006 14:20:00 -0800 36:37 http://online.kitp.ucsb.edu/online/grb_c06/fransson/ Claes Fransson (Stockholm Obs.) (Claes Fransson (Stockholm Obs.)) Claes Fransson (Stockholm Obs.) http://online.kitp.ucsb.edu/online/grb_c06/fransson/ Wed, 08 Feb 2006 10:50:00 -0800 34:36 http://online.kitp.ucsb.edu/online/grb_c06/ghavamian/ Parviz Ghavamian (JHU) (Parviz Ghavamian (JHU)) Parviz Ghavamian (JHU) Parviz Ghavamian (JHU) Parviz Ghavamian (JHU) (Thu, 09 Feb 2006 14:20) Our understanding of astrophysical collisionless shocks is limited because they occur in conditions too extreme to model in terrestrial laboratories.The plasma processes responsible for heating and isotropizing the electron and ion distributions at the shock front are poorly understood. In cases where the collisionless shock is non-radiative (adiabatic) and propagates into partially neutralgas, the excitation of cold hydrogen and charge exchange with hot ions close to the shock frontproduces both narrow and broad lines in the optical (Balmer emission) and UV (Lyman emission). The excitation of heavy ions (He, C, N and O) alsoproduces broad emission lines in the optical and UV range. I will show how spectroscopy of non-radiative supernova remnants provides valuable diagnostics of the plasma heating processes in highMach number interstellar shocks. The observations can be compared with predictions from numerical shock models to (1) infer the degree of electron-ion and ion-ion temperatureequilibration in collisionless shocks from the emission line widths and flux ratios, and (2) gain clues to the collisionless heating mechanism(s) from the shapes of the broad hydrogen line profiles. http://online.kitp.ucsb.edu/online/grb_c06/ghavamian/ Thu, 09 Feb 2006 14:20:00 -0800 40:48 http://online.kitp.ucsb.edu/online/grb_c06/granot/ Jonathan Granot (KIPAC/SLAC) (Jonathan Granot (KIPAC/SLAC)) Jonathan Granot (KIPAC/SLAC) Jonathan Granot (KIPAC/SLAC) Jonathan Granot (KIPAC/SLAC) (Mon, 06 Feb 2006 12:10) The structure of GRB jets has important implications for their energy budget and event rate, as well as for the mechanism responsible forthe collimation and acceleration of the outflow. I review our current understanding of the structure of GRB jets and their dynamics as they sweep up the external medium and decelerate. A good understanding of the jet dynamics is important in order to use afterglow observations to constrain the jet structure and energy, as well as the external density and its radial profile, and the micro-physical parameters of the afterglow shock. I end by briefly commenting about the possibleimplications of recent early X-ray observations by Swift for the energy budget of GRBs for different jet structures. http://online.kitp.ucsb.edu/online/grb_c06/granot/ Mon, 06 Feb 2006 12:10:00 -0800 37:05 http://online.kitp.ucsb.edu/online/grb_c06/hughes/ John P. Hughes (Rutgers) (John P. Hughes (Rutgers)) John P. Hughes (Rutgers) http://online.kitp.ucsb.edu/online/grb_c06/hughes/ Mon, 06 Feb 2006 09:00:00 -0800 34:05 http://online.kitp.ucsb.edu/online/grb_c06/hungerford/ Aimee Hungerford (LANL) (Aimee Hungerford (LANL)) Aimee Hungerford (LANL) Aimee Hungerford (LANL) Aimee Hungerford (LANL) (Tue, 07 Feb 2006 11:30) The distribution and abundance of elements synthesized during the explosion of a core collapse supernova are critical parameters in understanding the chemical evolution of galaxies and the stellar populations within the galaxy. The presence of explosion asymmetries in supernovae alters both the extent of the hydrodynamically mixed regions, as well as the conditions for burning within the supernova shock. This serves to change both the distribution and abundance of the ejected elements. Additionally, asymmetries in the remaining proto-neutron star affect the r-process synthesis of very heavy elements. In this talk, I will discuss trends in burning processes for a range of physical conditions which exist in core-collapse supernova simulations. Intuition gained from 1D explosion simulations will be compared against preliminary results from a 3D explosion simulation. http://online.kitp.ucsb.edu/online/grb_c06/hungerford/ Tue, 07 Feb 2006 11:30:00 -0800 41:59 http://online.kitp.ucsb.edu/online/grb_c06/immler/ Stefan Immler (GSFC/NASA/USRA) (Stefan Immler (GSFC/NASA/USRA)) Stefan Immler (GSFC/NASA/USRA) Stefan Immler (GSFC/NASA/USRA) Stefan Immler (GSFC/NASA/USRA) (Tue, 07 Feb 2006 14:20) Recent results from high-energy observations of young supernovae (SNe) in the SWIFT, Chandra, and XMM-Newton era are presented.A coherent picture regarding the CSM structure is slowly emerging from long-term X-ray monitoring programs, which indicates that the CSM profiles are strikingly similar for all core-collapse SNe out to large radii (>E18 cm) from the sites of the explosions. Establishing the long-term X-ray lightcurves also allows to study the spectral evolution from a hard spectral component originating in the forward shock at early times to the emergence of soft X-rays from the reverse shock. Our long-term programs to monitor the X-ray evolution of decades old SNe such as SNe 1970G, 78K and 79C allow, forthe first time, to directly witness the transition from a SN into a SNR. http://online.kitp.ucsb.edu/online/grb_c06/immler/ Tue, 07 Feb 2006 14:20:00 -0800 24:48 http://online.kitp.ucsb.edu/online/grb_c06/janka/ Thomas Janka (MPA, Garching) (Thomas Janka (MPA, Garching)) Thomas Janka (MPA, Garching) Thomas Janka (MPA, Garching) Thomas Janka (MPA, Garching) (Tue, 07 Feb 2006 09:40) Hydrodynamic instabilities -- of convective nature or based on the action of a vortical-acoustic cycle or pressure-wave amplification -- in the neutrino-heated postshock layer during the phase of shock stagnation can grow to global asymmetries of neutrino-driven supernova explosions. The talk discusses the status of the numerical modeling andthe possible implications of these instabilities for pulsar kicks and observable anisotropies of core-collapse supernovae. In particular, simulations are presented which demonstrate that major observational properties of SN 1987A may be explained by such instabilities without invoking rapid rotation in the core of the exploding star. http://online.kitp.ucsb.edu/online/grb_c06/janka/ Tue, 07 Feb 2006 09:40:00 -0800 40:29 http://online.kitp.ucsb.edu/online/grb_c06/kirk/ John Kirk (MPI, Heidelberg) (John Kirk (MPI, Heidelberg)) John Kirk (MPI, Heidelberg) John Kirk (MPI, Heidelberg) John Kirk (MPI, Heidelberg) (Thu, 09 Feb 2006 10:50) I will review the status of theory of the first order Fermi acceleration mechanism at relativistic shocks. Recent Monte-Carlo simulations that challenge the results of the simple kinematicapproach will be discussed. These raise deeper questions concerning the nature of the transport process in the magnetic fields generated by shock fronts. http://online.kitp.ucsb.edu/online/grb_c06/kirk/ Thu, 09 Feb 2006 10:50:00 -0800 33:04 http://online.kitp.ucsb.edu/online/grb_c06/kulkarni/ Shrinivas Kulkarni (Caltech) (Shrinivas Kulkarni (Caltech)) Shrinivas Kulkarni (Caltech) http://online.kitp.ucsb.edu/online/grb_c06/kulkarni/ Mon, 06 Feb 2006 09:00:00 -0800 38:20 http://online.kitp.ucsb.edu/online/grb_c06/kumar/ Pawan Kumar (Univ. Texas) (Pawan Kumar (Univ. Texas)) Pawan Kumar (Univ. Texas) Pawan Kumar (Univ. Texas) Pawan Kumar (Univ. Texas) (Wed, 08 Feb 2006 10:50) I will provide an overview of our understanding of the environment within about one parsec of gamma-ray bursts. Evidence for and against the presence of a stratified medium carved out by theprogenitor star's wind will be described. http://online.kitp.ucsb.edu/online/grb_c06/kumar/ Wed, 08 Feb 2006 10:50:00 -0800 39:34 http://online.kitp.ucsb.edu/online/grb_c06/laming/ Martin Laming (NRL) (Martin Laming (NRL)) Martin Laming (NRL) Martin Laming (NRL) Martin Laming (NRL) (Tue, 07 Feb 2006 12:10) In April-May 2004 the instruments on the Chandra X-ray observatory acquired an unprecedented deep integration of the Cassiopeia A supernova remnant, for a total of 1 million seconds. I will present the results of an initial analysis of the so-called \"jet\" regions of the remnants, and review analyses of earlier data from the Chandra archive, with a view to highlighting aspects of the explosion asymmetry that are visible today in the morphology and spectra of the remnant. In particular from x-ray spectroscopy, we canshow that the \"jets\" are indeed associated with asymmetry of the explosion as opposed to asymmetry in the circumstellar medium, and start to place numbers on the various parameters involved. We also make initial inferences on asymmetries in the Fe/Si inner ejecta and their possible relation to the direction of the compact central object natal kick. http://online.kitp.ucsb.edu/online/grb_c06/laming/ Tue, 07 Feb 2006 12:10:00 -0800 40:40 http://online.kitp.ucsb.edu/online/grb_c06/langer/ Norbert Langer (Utrecht Univ.) (Norbert Langer (Utrecht Univ.)) Norbert Langer (Utrecht Univ.) http://online.kitp.ucsb.edu/online/grb_c06/langer/ Wed, 08 Feb 2006 10:50:00 -0800 19:55 http://online.kitp.ucsb.edu/online/grb_c06/medvedev/ Mikhail Medvedev (Univ. Kansas) (Mikhail Medvedev (Univ. Kansas)) Mikhail Medvedev (Univ. Kansas) Mikhail Medvedev (Univ. Kansas) Mikhail Medvedev (Univ. Kansas) (Thu, 09 Feb 2006 11:30) Supernova, gamma-ray bursts and other violent cosmic phenomenaare known (or believed) to drive strong, relativistic or sub-relativistic shocks. Unlike the standard hydrodynamic shocks mediated by particle-particle collisions, these shocks are collisionless and, hence, involve more complicated electromagnetic processes. Despite this, we often continue to use the hydrodynamic models to compare with observations. In this talk we will discuss important theoretical ideas developed recently in this field, and the role of the Weibel instability, in particular. We will then link them to the observational aspects, e.g., the radiation processes, the physics jitter radiation, and the effects relativistic kinematics on the observed spectra. http://online.kitp.ucsb.edu/online/grb_c06/medvedev/ Thu, 09 Feb 2006 11:30:00 -0800 38:44 http://online.kitp.ucsb.edu/online/grb_c06/nomoto/ Ken'ichi Nomoto (Tokyo) (Ken'ichi Nomoto (Tokyo)) Ken'ichi Nomoto (Tokyo) Ken'ichi Nomoto (Tokyo) Ken'ichi Nomoto (Tokyo) (Wed, 08 Feb 2006 10:50) Authors: K. Nomoto, N. Tominaga, P.A. Mazzali, J. Deng, K. Maeda, M. Tanaka(Tokyo), and M. Modjaz, R.P. Kirshner (CfA) Observations and modeling for the light curve (LC) and spectra ofsupernova (SN) 2005bf are reported. This SN showed unique features: theLC had two maxima, and declined rapidly after the second maximum, whilethe spectra showed strengthening He lines whose velocityincreased with time. The double-peaked LC can be reproduced by adouble-peaked 56Ni distribution, with most 56Ni at low velocity and asmall amount at high velocity. The rapid post-maximum declinerequires a large fraction of the gamma-rays to escape from the56Ni-dominated region, possibly because of low-density ``holes''. Thepresence of Balmer lines in the spectrum suggests that the He layer of theprogenitor was substantially intact. Increasing gamma-raydeposition in the He layer due to enhanced gamma-ray escape from the56Ni-dominated region may explain both the delayed strengthening and theincreasing velocity of the He lines. The SN has massive ejecta (6-7Msun), normal kinetic energy (1.0-1.5 E51 ergs), high peakbolometric luminosity (5 E42 erg/s) for an epoch as late as 40 days, and alarge 56Ni mass (0.3 Msun). These properties, and the presence of a smallamount of H suggest that the progenitor was initiallymassive (25-30 Msun) and had lost most of its H envelope, possibly a WNstar. The double-peaked 56Ni distribution suggests that theexplosion may have formed jets that did not reach the He layer.The properties of SN 2005bf resemble those of the explosion ofCassiopeia A. http://online.kitp.ucsb.edu/online/grb_c06/nomoto/ Wed, 08 Feb 2006 10:50:00 -0800 20:54 http://online.kitp.ucsb.edu/online/grb_c06/pakull/ Manfred Pakull (France) (Manfred Pakull (France)) Manfred Pakull (France) Manfred Pakull (France) Manfred Pakull (France) (Tue, 07 Feb 2006 14:20) An interesting result from the optical study of ultraluminous (i.e. L_x 10^39.5 erg/s) variable X-ray sources in nearby galaxies has been the discovery of huge (several hundred pc diameter (!)) bubble-like emission nebulae surrounding these objects. From the measured line widths (corresponding to ~ 100 km/s) and diagnostic emission-line ratios (e.g. [OI]6300/H_alpha > 0.3) we find that these ULX bubbles are young (<10**6 yrs), largely shock-excited structures, although there is also evidence for contribution from (X-ray) photoionisation close to the sources. Using SUBARU, ESO-VLT and HST photometry of the recently identified underlying poor star clusters to which the ULXs belong, stellar isochrones yield cluster ages of some 20--60 Myrs proving that the stellar population is much older than the ULX bubbles.Straightforward application of adiabatic SNR or wind-bubble dynamics, plus an estimate of the interstellar density from the observed recombination line luminosity of radiative shocks, yields ULX bubble energies of some 10^53 erg. This is much larger than the kinetic energy of a single SNR, and more than the superbubble history from the cluster could have possibly provided during its entire lifetime, let alone during the past 10^6 yrs.Taking into account the effects of a clumpy, rather than uniform ISM and of expansion of the shocks into previously excavated stellar wind bubbles, the energy requirements could be lessened by a factor of ten. This is still much higher than the 10^51 erg kinetic energy of a SN explosion, but is comparable to what has been claimed for \"hypernova\" remnants. However, inspired by the properties of the famous SS433/W50 system and the largely \"dark jets\" from galactic black hole binaries, I will present evidence for ongoing inflation of ULX bubbles by relativistic jets emanating from the presumed accreting black holes in ULXs.Finally, our optical search for nebula around ULXs that are currently X-ray inactive, or that are possibly beamed away from our line-of-sight, has revealed at least one very large (> 200 pc diameter) [OI]6300 bright, i.e. shock-excited, nebula in the nearby spiral NGC~1313. We will discuss these results in the light of current knowledge of past and ongoing energetic input of black-hole binaries into the ISM. http://online.kitp.ucsb.edu/online/grb_c06/pakull/ Tue, 07 Feb 2006 14:20:00 -0800 18:49 http://online.kitp.ucsb.edu/online/grb_c06/proga/ Daniel Proga (UNLV) (Daniel Proga (UNLV)) Daniel Proga (UNLV) Daniel Proga (UNLV) Daniel Proga (UNLV) (Mon, 06 Feb 2006 10:50) I review recent results from numerical simulations of a magnetized flow in the vicinity of a black hole in the context of the collapsar model for GRBs.The simulations show that after an initial transient, the flow settles intoa complex convolution of several distinct flow components. I discuss the nature and connection between these components, in particular between the inflows and related outflows. I also discuss how and under what conditions the collapsing stellar envelope can trigger a very strong and fast outflow that can become a super-relativistic jet. http://online.kitp.ucsb.edu/online/grb_c06/proga/ Mon, 06 Feb 2006 10:50:00 -0800 43:38 http://online.kitp.ucsb.edu/online/grb_c06/rakowski/ Cara Rakowski (Harvard-Smithsonian CfA) (Cara Rakowski (Harvard-Smithsonian CfA)) Cara Rakowski (Harvard-Smithsonian CfA) Cara Rakowski (Harvard-Smithsonian CfA) Cara Rakowski (Harvard-Smithsonian CfA) (Fri, 10 Feb 2006 14:20) Collisionless plasmas are a common feature of many astrophysical systems (e.g. active galactic nuclei, supernova remnants, clusters of (galaxies) and exhibit unique properties stemming from the loose coupling between particle species and the plasma instabilities that can accelerate some species efficiently and others not at all. Supernova remnant shocks are efficient particle accelerators and may be responsible for the bulk of cosmic rays below 1000 TeV. Galactic and Magellanic Cloud remnants are close enough that the Chandra X-ray observatory has enabled us to spatially resolve theshock heated material as it relaxes downstream. A complete picture of the particle acceleration in collisionless shocks requires the examination of the magnetic field, the thermal and cosmic raypopulations of protons, ion and electrons, and the dynamical effects of magnetic field amplification and cosmic ray losses. In this talk I will focus on the diagnostic capabilities of X-ray spectralobservations of the thermal plasma advecting away from the shock to determine not only the initial electron heating at the shock front butalso to see the effects of the elusive cosmic-ray ions. http://online.kitp.ucsb.edu/online/grb_c06/rakowski/ Fri, 10 Feb 2006 14:20:00 -0800 33:16 http://online.kitp.ucsb.edu/online/grb_c06/reeves/ James Reeves (GSFC) (James Reeves (GSFC)) James Reeves (GSFC) James Reeves (GSFC) James Reeves (GSFC) (Mon, 06 Feb 2006 16:10) The evidence for X-ray line emission in GRB afterglows is reviewed. Evidence from XMM-Newton observations of GRB afterglows has showed moderate statistical significance soft X-ray lines in at least 3 GRB afterglows, GRB 011211, GRB 030227 and GRB 040106. Blue-shifted soft X-ray lines from Si, S, Ar were originally claimed in GRB 011211, which was interpreted as emission from hot, outflowing gas around the GRB progenitor, possibly originating from a supernova explosion. The statistical significance of the line features. e.g. through Monte Carlo simulations, will be addressed. Preliminary results from the afterglow spectra provided by Swift XRT will also be presented. A small number of these afterglows may show evidence for a soft X-ray excess, while a large proportion show excess X-ray absorption. None of the afterglows appear to show evidence for Fe line emission, in contrast with very early afterglow spectra obtained by Beppo-SAX, ASCA and Chandra, but in agreement with the XMM-Newton observations. The potential for detecting X-ray line features at higher statistical significance will be discussed. http://online.kitp.ucsb.edu/online/grb_c06/reeves/ Mon, 06 Feb 2006 16:10:00 -0800 31:22 http://online.kitp.ucsb.edu/online/grb_c06/romani/ Roger Romani (Stanford) (Roger Romani (Stanford)) Roger Romani (Stanford) Roger Romani (Stanford) Roger Romani (Stanford) (Tue, 07 Feb 2006 10:50) Chandra X-ray imaging has shown that equatorial tori, often with polar jets, are very common in young pulsar wind nebulae (PWNe). We review how simple models of these toroidal structures can provide (nearly) model-independent measurements of the neutron star spin orientation. Abetted by recent progress in measuring pulsar proper motions and ininterpreting polarization observations, the PWN images give a set of young pulsars for which we can compare the linear and spin angular momentum vectors. If preserved since core collapse, these vectors give an important new handle on kick dynamics and, less directly, core collapse physics. Early modeling of the data set shows significant constraint on the pulsar initial spin and kick amplitude and timescale. We comment briefly on other kick constraints and onthe connection with core modeling. http://online.kitp.ucsb.edu/online/grb_c06/romani/ Tue, 07 Feb 2006 10:50:00 -0800 36:11 http://online.kitp.ucsb.edu/online/grb_c06/sako/ Masao Sako (KIPAC/SLAC) (Masao Sako (KIPAC/SLAC)) Masao Sako (KIPAC/SLAC) Masao Sako (KIPAC/SLAC) Masao Sako (KIPAC/SLAC) (Mon, 06 Feb 2006 16:50) The detection of discrete X-ray spectral features during the afterglows of gamma-ray burst is an important and difficult measurement, which will undoubtedly provide indispensable clues to help us understand the physical nature of the burst progenitor star. Several interesting cases have been reported, but the reality of the detections as well as their identifications and interpretations remain rather controversial. I will give a brief review the current status of X-ray emission line detections in GRB afterglows, some of the existing models, and the prospects for detecting them with present and future observatories.v http://online.kitp.ucsb.edu/online/grb_c06/sako/ Mon, 06 Feb 2006 16:50:00 -0800 28:50 http://online.kitp.ucsb.edu/online/grb_c06/soderberg/ Alicia Soderberg (Caltech) (Alicia Soderberg (Caltech)) Alicia Soderberg (Caltech) Alicia Soderberg (Caltech) Alicia Soderberg (Caltech) (Tue, 07 Feb 2006 14:20) With the launch of the Swift satellite in 2004, great strides have been made toward understanding the once mysterious gamma-raybursts. By studying their X-ray, optical and radio afterglows, we have been able to derive the energy of the explosion, the geometry of the outflow, the density structure of the circumburst medium, and the properties of their host galaxies. Although many questions remain unanswered, a basic picture is beginning to emerge in which long-duration gamma-ray bursts originate from the birth of a black hole. The subsequent explosion, with a typical energy of 10^51 erg, drives a highly collimated, ultra-relativistic shock in thecircumburst medium with a density of order 1 cm-3. We now know that most long duration GRBs are also accompanied by a sub-relativisticquasi-spherical explosion which gives rise to a Type Ibc supernova. In this talk, I will illustrate how radio observations of GRB afterglows have enabled this progress to be achieved. In addition I will discuss how radio observations of local Type Ibc supernovae can be used as a unique tool to shed light on the GRB-SN connection. In particular, I will present the radio derived constraints on the energy coupled to relativistic ejecta from our survey of ~100 local SNe Ibc which impose severe constraints on the \"hypernova\" model. http://online.kitp.ucsb.edu/online/grb_c06/soderberg/ Tue, 07 Feb 2006 14:20:00 -0800 40:21 http://online.kitp.ucsb.edu/online/grb_c06/vandyk/ Schuyler D. Van Dyk (Caltech) (Schuyler D. Van Dyk (Caltech)) Schuyler D. Van Dyk (Caltech) Schuyler D. Van Dyk (Caltech) Schuyler D. Van Dyk (Caltech) (Tue, 07 Feb 2006 14:20) Using primarily the Hubble Space Telescope we have been identifying the massive progenitor stars that give rise to core-collapse supernovae, which is one of the main pursuits of supernova and stellar evolution studies. Prime examples of this are the Type II-plateau supernovae SN 2003gd in M74 and SN 2005cs in M51. Upper limits on progenitor masses for both Type II and Type Ib/c supernovae have also been established using HST image data by us and by other groups. I would summarize this work and what we know to date. http://online.kitp.ucsb.edu/online/grb_c06/vandyk/ Tue, 07 Feb 2006 14:20:00 -0800 15:04 http://online.kitp.ucsb.edu/online/grb_c06/vink/ Jacco Vink (SRON) (Jacco Vink (SRON)) Jacco Vink (SRON) Jacco Vink (SRON) Jacco Vink (SRON) (Thu, 09 Feb 2006 16:10) Due to Chandra's capabilities for imaging spectroscopy with very high spatial resolution, it has become clear over the last five years that virtually all young supernova remnants emit X-ray synchrotron radiation from a region close to the shock front. The X-ray synchrotron radiation is confined to a region close to the shock front, because the X-ray radiation comes from the highest energy electrons for which radiation loss time scales are short.
The width of the X-ray synchrotron region varies, for example it is small (few arcsec) for Cas A and Tycho, but quite extended for RCW 86 and SN1006. These widths have been interpreted in two ways, both of which can be used to obtain an estimate of the downstream magnetic field strength: 1) The widths corresponds to the time scale over which the advected electrons lose so much energy that they stop emitting X-ray radiation (the advection length scale); i.e. width = v_p *t_x, with v_p the plasma velocity and t_xthe X-ray loss time scale. 2) Alternatively, one can assume that the widths correspond the the diffusion length scale. For the advection length scale one has to assume a plasma velocity based on the (sometimes measured) shock velocity, usually v_p = 1/4v_s, but high shock compression may change this.
For the diffusion length scale method one has to assume a diffusion coefficient; usually the diffusion is assumed to be at the Bohm limit, which is the fastest diffusion possible. However, I will show that for the highest electron energiesin the loss limited case the two different length scales should be roughly equal. This is in agreement with the fact that both methods give similar values for the magnetic field strength near the shock front, and that the spectra are steep. However, the insistency of the results also suggests that the assumptions made, i.e. Bohm diffusion, are indeed valid.
The high magnetic field strength estimated in conjunction with the evidence for Bohm diffusion indicates that young supernova remnants must be capable of acceleration ions well above the cosmic ray \"knee\" (3x10^15 eV). Moreover, the rough scaling of B with the density and shock velocity suggests that the highest energies are reached early in the life of a SNR and preferentially inshocks moving through a red supergiant wind.
Finally, I will show evidence that a simple extrapolation of the radio synchrotron spectrum including an exponential cut-off cannot describe the X-ray synchrotron spectra of Cas A and RCW 86. Instead a flattening of the spectrum has to be assumed in agreement with non-linear shock acceleration theory. http://online.kitp.ucsb.edu/online/grb_c06/vink/ Thu, 09 Feb 2006 16:10:00 -0800 41:04 http://online.kitp.ucsb.edu/online/grb_c06/wang/ Lifan Wang (LBNL) (Lifan Wang (LBNL)) Lifan Wang (LBNL) http://online.kitp.ucsb.edu/online/grb_c06/wang/ Mon, 06 Feb 2006 14:20:00 -0800 38:12 http://online.kitp.ucsb.edu/online/grb_c06/warren/ Jessica Warren (Rutgers) (Jessica Warren (Rutgers)) Jessica Warren (Rutgers) Jessica Warren (Rutgers) Jessica Warren (Rutgers) (Fri, 10 Feb 2006 11:30) The Chandra megasecond observation of Cas A allows for a spectrum to be obtained from every pixel of the CCD. The question of where to begin the analysis and the corresponding answers that can be gleaned from the data are potentially overwhelming. One way to get a handle on the data is with a principal component analysis (PCA). PCA is a mathematical technique used to reduce the dimensionality of a dataset. It compares spectra from different regions in an SNR and identifies those that vary significantly from the average spectrum in some way. This technique has already proven successful in the study of Tycho$apos;s SNR. I will discuss the method of PCA and how it is applied to SNRs, specifically the Cas A megasecond data. I will present some preliminary results, with an eye toward areas that warrant further investigation. http://online.kitp.ucsb.edu/online/grb_c06/warren/ Fri, 10 Feb 2006 11:30:00 -0800 24:25 http://online.kitp.ucsb.edu/online/grb_c06/weiler/ Kurt Weiler (NRL) (Kurt Weiler (NRL)) Kurt Weiler (NRL) Kurt Weiler (NRL) Kurt Weiler (NRL) (Wed, 08 Feb 2006 09:00) The study of radio emission from extragalactic supernovae has resulted in the detection of a few tens of examples of Type Ib/c and Type II SNe ofvarious sub-classes. No Type Ia supernova has ever been detected in the radio. Approaching 200 SNe of all types and sub-types have been studiedwithout detection over the same interval.Out of this extensive study of the radio emission from supernovae, several general observations can be made: (1) Type Ia SNe are not radio emitters tothe detection limit of the VLA; (2) Type Ib/c SNe are radio luminous with steep spectral indices (generally, spectral index < -1) and a fastturn-on/turn-off, usually peaking at 6 cm near or before optical maximum; (3) Type II SNe (with various optically determined sub-types) show a range of radio luminosities with flatter spectral indices (generally, spectral index > -1) and a relatively slow turn-on/turn-off, usually peaking at 6 cm significantly after optical maximum; and (4) At least some type Ib/c SNe are related to the ``soft-slow'' subclass of gamma-ray bursters (GRBs).From the radio data it is possible to classify the properties of supernovae and to develop and test models for the radio emission which match the light curves. Among the results of this work are estimates of the density and structure of the circumstellar material, the density evolution of thepresupernova stellar wind, and insight into the last stages of stellar evolution before the explosion. http://online.kitp.ucsb.edu/online/grb_c06/weiler/ Wed, 08 Feb 2006 09:00:00 -0800 39:02 http://online.kitp.ucsb.edu/online/grb_c06/young/ Patrick Young (LANL) (Patrick Young (LANL)) Patrick Young (LANL) Patrick Young (LANL) Patrick Young (LANL) (Fri, 10 Feb 2006 09:40) Despite the wealth of observational data available for Cassiopeia A, the suggestions for its progenitor span a wide array of stellar types. We compare a suite of 3D explosion calculations and stellar models incorporating advanced physics with observational constraints on the progenitor. We consider binary and single stars from 16 to 40 \sol with a range of explosion energies and geometries. The parameter space allowed by observations of nitrogen rich high velocity ejecta, ejecta mass, compact remnant mass, and $^{44}$Ti and $^{56}$Ni abundances individually and as an ensemble is considered. A progenitor of 15-25 \sol which loses its hydrogen envelope to a binaryinteraction and undergoes an energetic explosion can match all the observational constraints. http://online.kitp.ucsb.edu/online/grb_c06/young/ Fri, 10 Feb 2006 09:40:00 -0800 35:49 http://online.kitp.ucsb.edu/online/grb_c06/zhang/ Weiqun Zhang (KIPAC/SLAC) (Weiqun Zhang (KIPAC/SLAC)) Weiqun Zhang (KIPAC/SLAC) Weiqun Zhang (KIPAC/SLAC) Weiqun Zhang (KIPAC/SLAC) (Mon, 06 Feb 2006 11:30) In this talk, I will discuss numerical simulations of relativistic jets in massive stars in the context of the collapsar model for long soft gamma-ray bursts. The propagation and breakout of such jets are examined in multi-dimensional special relativistic hydrodynamical simulations. During its propagation, the jet is collimated by the passage through the stellar mantle. As it erupts, the highlyrelativistic jet core is surrounded by a cocoon of less energetic, but still moderately relativistic ejecta that expands and becomes visible at larger polar angles. Implications for both the observations and the models which generate the jets are discussed. http://online.kitp.ucsb.edu/online/grb_c06/zhang/ Mon, 06 Feb 2006 11:30:00 -0800 33:55