Very High Energy Emission From Supernovae and Supernova Remnants

 

The transport and acceleration of test particles in hydrodynamical simulations


Duffy, P.; Dwarkadas, V.; Ball, L.


Proceedings of the 27th International Cosmic Ray Conference. 07-15 August, 2001. Hamburg, Germany. Under the auspices of the International Union of Pure and Applied Physics (IUPAP)., p.2046


08/2001


2001ICRC....6.2046D

Abstract

The interaction of supernovae with their surroundings has been studied with hydrodynamical codes which capture the shock waves produced when the ejecta interact with the medium close to the progenitor star. Observationally it is known that core-collapse supernovae, of which SN1987A and SN1993J are two well-studied examples, emit nonthermal radiation which is associated with electron acceleration at these shock waves. We present a model for the transport and acceleration of test particles in hydrodynamical simulations of young radio supernovae.

Observation of Extended Very High Energy Emission from the Supernova Remnant IC 443 with VERITAS


Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M.; Benbow, W.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; and 82 coauthors


The Astrophysical Journal Letters, Volume 698, Issue 2, pp. L133-L137 (2009).


06/2009

Origin:



2009ApJ...698L.133A

Abstract

We present evidence that the very high energy (VHE, E > 100 GeV) gamma-ray emission coincident with the supernova remnant IC 443 is extended. IC 443 contains one of the best studied sites of supernova remnant/molecular cloud interaction and the pulsar wind nebula CXOU J061705.3+222127, both of which are important targets for VHE observations. VERITAS observed IC 443 for 37.9 hr during 2007 and detected emission above 300 GeV with an excess of 247 events, resulting in a significance of 8.3 standard deviations (σ) before trials and 7.5σ after trials in a point-source search. The emission is centered at 6h16m51s + 22°30'11'' (J2000) ±0fdg03stat ± 0fdg08sys, with an intrinsic extension of 0fdg16 ± 0fdg03stat ± 0fdg04sys. The VHE spectrum is well fit by a power law (dN/dE = N 0 × (E/TeV)-Γ) with a photon index of 2.99 ± 0.38stat ± 0.3sys and an integral flux above 300 GeV of (4.63 ± 0.90stat ± 0.93sys) × 10-12 cm-2 s-1. These results are discussed in the context of existing models for gamma-ray production in IC 443.

Particle spectra from acceleration at forward and reverse shocks of young Type Ia Supernova Remnants


Telezhinsky, I.; Dwarkadas, V. V.; Pohl, M.


Astroparticle Physics, 2012, Volume 35, Issue 6, p. 300-311


We study cosmic-ray acceleration in young Type Ia Supernova Remnants (SNRs) by means of test-particle diffusive shock acceleration theory and 1-D hydrodynamical simulations of their evolution. In addition to acceleration at the forward shock, we explore the particle acceleration at the reverse shock in the presence of a possible substantial magnetic field, and consequently the impact of this acceleration on the particle spectra in the remnant. We investigate the time evolution of the spectra for various time-dependent profiles of the magnetic field in the shocked region of the remnant. We test a possible influence on particle spectra of the Alfvénic drift of scattering centers in the precursor regions of the shocks. In addition, we study the radiation spectra and morphology in a broad band from radio to gamma-rays. It is demonstrated that the reverse shock contribution to the cosmic-ray particle population of young Type Ia SNRs may be significant, modifying the spatial distribution of particles and noticeably affecting the volume-integrated particle spectra in young SNRs. In particular spectral structures may arise in test-particle calculations that are often discussed as signatures of non-linear cosmic-ray modification of shocks. Therefore, the spectrum and morphology of emission, and their time evolution, differ from pure forward-shock solutions.

Time-dependent escape of cosmic rays from supernova remnants, and their interaction with dense media


Telezhinsky, I.; Dwarkadas, V. V.; Pohl, M


Astronomy & Astrophysics, 2012, Volume 541, id.A153, 11 pp


Context. Supernova remnants (SNRs) are thought to be the main source of Galactic cosmic rays (CRs) up to the "knee" in CR spectrum. During the evolution of a SNR, the bulk of the CRs are confined inside the SNR shell. The highest-energy particles leave the system continuously, while the remaining adiabatically cooled particles are released when the SNR has expanded sufficiently and decelerated so that the magnetic field at the shock is no longer able to confine them. Particles escaping from the parent system may interact with nearby molecular clouds, producing γ-rays in the process via pion decay. The soft gamma-ray spectra observed for a number of SNRs interacting with molecular clouds, however, challenge current theories of non-linear particle acceleration that predict harder spectra.

Aims: We study how the spectrum of escaped particles depends on the time-dependent acceleration history in both Type Ia and corecollapse SNRs, as well as on different assumptions about the diffusion coefficient in the vicinity of the SNR.

Methods: We solve the CR transport equation in a test-particle approach combined with numerical simulations of SNR evolution.

Results: We extend our method for calculating the CR acceleration in SNRs to trace the escaped particles in a large volume around SNRs. We calculate the evolution of the spectra of CRs that have escaped from a SNR into a molecular cloud or dense shell for two diffusion models. We find a strong confinement of CRs in a close region around the SNR, and a strong dilution effect for CRs that were able to propagate out as far as a few SNR radii.

On the maximum energy and escape of accelerated particles in young supernova remnants


Dwarkadas, Vikram V.; Telezhinsky, Igor; Pohl, Martin


HIGH ENERGY GAMMA-RAY ASTRONOMY: 5th International Meeting on High Energy Gamma-Ray Astronomy. AIP Conference Proceedings, Volume 1505, pp. 245-248 (2012).



Using analytic expressions and self-similar solutions, we explore different environments in which supernova remnants (SNRs) evolve, and investigate how the maximum energy to which particles are accelerated, and its time evolution, is a function of the complex environment. We take into account the ambient magnetic field and its amplification by resonant or non-resonant modes. We find that particles reach the maximum energies in the ejecta-dominated stage, much earlier than Sedov stage, particularly in the case of core-collapse SNe expanding in the winds of massive stars.

Discovery of TeV Gamma-Ray Emission from CTA 1 by VERITAS



Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Gotthelf, E. V.; Griffin, S.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Kargaltsev, O.; Karlsson, N.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Lee, K.; Madhavan, A. S.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nelson, T.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Orr, M.; Otte, A. N.; Park, N.; Perkins, J. S.; Pohl, M.; Prokoph, H.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Roberts, M.; Saxon, D. B.; Schroedter, M.; Sembroski, G. H.; Slane, P.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tešić, G.; Theiling, M.; Thibadeau, S.; Tsurusaki, K.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Vivier, M.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Welsing, R.; Williams, D. A.; Zitzer, B.



The Astrophysical Journal, Volume 764, Issue 1, article id. 38, 9 pp. (2013)


We report the discovery of TeV gamma-ray emission coincident with the shell-type radio supernova remnant (SNR) CTA 1 using the VERITAS gamma-ray observatory. The source, VER J0006+729, was detected as a 6.5 standard deviation excess over background and shows an extended morphology, approximated by a two-dimensional Gaussian of semimajor (semiminor) axis 0.°30 (0.°24) and a centroid 5' from the Fermi gamma-ray pulsar PSR J0007+7303 and its X-ray pulsar wind nebula (PWN). The photon spectrum is well described by a power-law dN/dE = N 0(E/3 TeV)-Γ, with a differential spectral index of Γ = 2.2 ± 0.2stat ± 0.3sys, and normalization N 0 = (9.1 ± 1.3stat ± 1.7sys) × 10-14 cm-2 s-1 TeV-1. The integral flux, F γ = 4.0 × 10-12 erg cm-2 s-1 above 1 TeV, corresponds to 0.2% of the pulsar spin-down power at 1.4 kpc. The energetics, colocation with the SNR, and the relatively small extent of the TeV emission strongly argue for the PWN origin of the TeV photons. We consider the origin of the TeV emission in CTA 1.

Acceleration of cosmic rays by young core-collapse supernova remnants


Telezhinsky, I.; Dwarkadas, V. V.; Pohl, M.


Astronomy & Astrophysics, Volume 552, id.A102, 12 pp.


Context. Supernova remnants (SNRs) are thought to be the primary candidates for the sources of Galactic cosmic rays. According to the diffusive shock acceleration theory, SNR shocks produce a power-law spectrum with an index of s = 2, perhaps nonlinearly modified to harder spectra at high energy. Observations of SNRs often indicate particle spectra that are softer than that and show features not expected from classical theory. Known drawbacks of the standard approach are the assumption that SNRs evolve in a uniform environment, and that the reverse shock does not accelerate particles. Relaxing these assumptions increases the complexity of the problem, because one needs reliable hydrodynamical data for the plasma flow as well as good estimates for the magnetic field (MF) at the reverse shock.

Aims: We show that these two factors are especially important when modeling young core-collapse SNRs that evolve in a complicated circumstellar medium shaped by the winds of progenitor stars.

Methods: We used high-resolution numerical simulations for the hydrodynamical evolution of the SNR. Instead of parametrizations of the MF profiles inside the SNR, we followed the advection of the frozen-in MF inside the SNR, and thus obtained the B-field value at all locations, in particular at the reverse shock. To model cosmic-ray acceleration we solved the cosmic-ray transport equation in test-particle approximation.

Results: We find that the complex plasma-flow profiles of core-collapse SNRs significantly modify the particle spectra. Additionally, the reverse shock strongly affects the emission spectra and the surface brightness.


VERITAS Observations of the Nova in V407 Cygni



Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bouvier, A.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Decerprit, G.; Dickherber, R.; Duke, C.; Dumm, J.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Godambe, S.; Griffin, S.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Huan, H.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Lee, K.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nuñez, P. D.; Ong, R. A.; Orr, M.; Otte, A. N.; Pandel, D.; Park, N.; Perkins, J. S.; Pohl, M.; Prokoph, H.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Ruppel, J.; Saxon, D. B.; Schroedter, M.; Sembroski, G. H.; Skole, C.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tešić, G.; Theiling, M.; Thibadeau, S.; Tsurusaki, K.; Tyler, J.; Varlotta, A.; Vincent, S.; Vivier, M.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Welsing, R.; Williams, D. A.; Zitzer, B.


The Astrophysical Journal, Volume 754, Issue 1, article id. 77, 7 pp. (2012)


We report on very high energy (E > 100 GeV) gamma-ray observations of V407 Cygni, a symbiotic binary that underwent a nova outburst producing 0.1-10 GeV gamma rays during 2010 March 10-26. Observations were made with the Very Energetic Radiation Imaging Telescope Array System during 2010 March 19-26 at relatively large zenith angles due to the position of V407 Cyg. An improved reconstruction technique for large zenith angle observations is presented and used to analyze the data. We do not detect V407 Cygni and place a differential upper limit on the flux at 1.6 TeV of 2.3 × 10-12 erg cm-2 s-1 (at the 95% confidence level). When considered jointly with data from Fermi-LAT, this result places limits on the acceleration of very high energy particles in the nova.

Discovery of TeV Gamma-Ray Emission toward Supernova Remnant SNR G78.2+2.1


Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bird, R.; Bouvier, A.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Dwarkadas, V. V.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Gotthelf, E. V.; Griffin, S.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Huan, H.; Hughes, G.; Humensky, T. B.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Lee, K.; Madhavan, A. S.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nelson, T.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Orr, M.; Otte, A. N.; Pandel, D.; Park, N.; Perkins, J. S.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Ruppel, J.; Saxon, D. B.; Schroedter, M.; Sembroski, G. H.; Şentürk, G. D.; Skole, C.; Telezhinsky, I.; Tešić, G.; Theiling, M.; Thibadeau, S.; Tsurusaki, K.; Tyler, J.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Welsing, R.; Williams, D. A.; Zitzer, B.


The Astrophysical Journal, Volume 770, Issue 2, article id. 93, 7 pp. (2013)


We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0{.\!\!^\circ }23 +/- {0{.\!\!^\circ }03_stat} {}^{+0{.\!\!^\circ }04}_{-0{.\!\!^\circ }02sys} and its spectrum is well-characterized by a differential power law (dN/dE = N 0 × (E/TeV)-Γ) with a photon index of Γ = 2.37 ± 0.14stat ± 0.20sys and a flux normalization of N 0 = 1.5 ± 0.2stat ± 0.4sys × 10-12 photon TeV-1 cm-2 s-1. This yields an integral flux of 5.2 ± 0.8stat ± 1.4sys × 10-12 photon cm-2 s-1 above 320 GeV, corresponding to 3.7% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the SNR shock.