TeV Particle Astrophysics 2013

Session

High-energy gamma rays

28 Aug 2013, 16:30

Beckman Center of the National Academies of Sciences and Engineering

Conveners

High-energy gamma rays

• Justin Vandenbroucke (University of Wisconsin, Madison)
• Brenda Dingus (LANL)

High-energy gamma rays

• Brenda Dingus (LANL)
• Justin Vandenbroucke (University of Wisconsin, Madison)

High-energy gamma rays

• Brenda Dingus (LANL)
• Justin Vandenbroucke (University of Wisconsin, Madison)

73. The Impact of Gamma-ray Halos on the Angular Anisotropy of the Extragalactic Gamma-ray Background

Tonia Venters

28/08/2013, 16:30

The study of the development of electromagnetic cascades in intergalactic magnetic fields (IGMF) serves as a robust probe into the strength and structure of these magnetic fields. Charged particles in electromagnetic cascades are deflected by magnetic fields giving rise to gamma-ray halos around extragalactic sources of VHE gamma rays (e.g., BL Lacertae-type objects). Such gamma-ray halos can...

74. The measurement of the expansion rate of the Universe from gamma-ray attenuation

Alberto Dominguez

28/08/2013, 16:54

The first statistically significant detection of the cosmic gamma-ray horizon (CGRH) that is independent of any extragalactic background light (EBL) model is presented in this talk. The CGRH is a fundamental quantity in cosmology. It gives an estimate of the opacity of the Universe to very-high energy (VHE) gamma-ray photons due to photon-photon pair production with the EBL. Our CGRH detection...

75. Constraining emission models with observations of the highest-energy gamma rays from the exceptional GRB 130427A

Taylor Aune

28/08/2013, 17:18

The prompt emission from the very bright and nearby gamma-ray burst GRB 130427A was detected by several orbiting telescopes and prompt optical emission was also detected from the ground. Observations of the afterglow emission from GRB 130427A show detections from radio to gamma-ray wavelengths and include well-sampled early afterglow lightcurves at optical and X-ray wavelengths. Apart from...

76. Search for high energy emission from GRBs with the HAWC Observatory

Dmitry Zaborov

28/08/2013, 17:42

The High Altitude Water Cherenkov Observatory (HAWC) is an air shower array currently under construction in Mexico at an altitude of 4100 m. HAWC will consist of 300 large water tanks covering an area of about 22000 square meters and instrumented with 4 photomultipliers each. HAWC's primary purpose is the observation of cosmic gamma-ray sources, including large extended sources and transient...

112. Multi-Wavelength Study of HESS J1809-193: Suzaku and Chandra Observations of the North-East Extension

Blagoy Rangelov

28/08/2013, 18:06

Multi-wavelength observations of the HESS J1809−193 field reveal a complex picture. Although the majority of the bright TeV emission can be attributed to the pulsar-wind nebula (PWN) of PSR J1809−1917, several supernova remnants, as well as another PWN, may contribute to the observed VHE emission. The H.E.S.S. image shows an extension toward north-east, which could be a separate TeV source. We...

63. The Fermi bubbles: foreground subtraction and energy spectrum

Dmitry Malyshev

29/08/2013, 14:00

The Fermi bubbles are a spectacular remnant of a past activity in or around the Galactic center. I will describe our analysis of the Fermi bubbles using 50 months of the Fermi-LAT data (pass7 reprocessed). One of the main challenges in the analysis is the separation of the Fermi bubbles from the other components of the Galactic diffuse emission. I will talk about two different methods to...

64. Search for Gamma-ray Spectral Lines with the Fermi Large Area Telescope

Andrea Albert

29/08/2013, 14:24

There is overwhelming evidence that non-baryonic dark matter constitutes ~27% of the energy density of the universe. Weakly Interacting Massive Particles are promising dark matter candidates that may produce monochromatic gamma rays via annihilation or decay. Such interactions would give a narrow spectral line in the Galactic diffuse gamma-ray energy spectrum. We have searched for spectral...

65. A GeV Gamma-Ray Spectral Feature in the Inner Galaxy

Tracy Slatyer

29/08/2013, 14:48

I will present evidence that the spectral feature in few-GeV diffuse gamma-rays previously identified in the Galactic Center (GC) extends to much higher Galactic latitudes, 5-20 degrees from the Galactic plane. I will discuss the spectrum and morphology of the signal and some systematic uncertainties in extraction of the spectrum, with their consequences for dark matter interpretations....

66. Disentangling Hadronic and Leptonic Cascade Scenarios from the Very-high-energy Gamma-ray Emission of Hard-spectrum Blazars

Hajime Takami

29/08/2013, 15:12

The very-high-energy (VHE; > 100 GeV) gamma-ray spectra of extreme high-frequency peaked BL Lac objects and distant hard-spectrum blazars can be well explained either by gamma rays emitted at the source or by cascades induced by ultra-high-energy cosmic rays. The confirmation of the hadronic scenario provides strong evidence for the origin of ultra-high-energy cosmic rays. In this talk, we...

67. Neutron-Proton-Conversion Acceleration at Subphotospheres of Relativistic Outflows

Kazumi Kashiyama

29/08/2013, 15:36

We study a type of particle acceleration that operates via neutron-proton conversion (NPC) in in- elastic nuclear collisions. This mechanism can be expected for relativistic shocks at subphotospheres if relativistic outflows contain neutrons. Using a test-particle approximation, we numerically calcu- late the energy spectrum and the efficiency of accelerated particles, and show that a good...

68. Relativistic MHD Simulations of Ponyting Flux-Driven Jets

Xiaoyue Guan

29/08/2013, 16:30

Relativistic, magnetized jets are observed to propagate to very large distances in many Active Galactic Nuclei (AGN). We use 3D relativistic MHD (RMHD) simulations to study the propagation of Ponyting flux-driven jets in AGN. These jets are assumed already being launched from the vicinity (~10^3 gravitational radii) of supermassive black holes and we follow the propagation of these jets to ~...

69. The Gamma-ray Spectrum of PKS 1424+240, the Most Distant TeV Source

David Williams

29/08/2013, 16:54

The very-high-energy (VHE) gamma-ray source PKS 1424+240, a blazar, has Lyman forest absorption in its UV spectrum out to a redshift of 0.6035, making it the most distant VHE gamma-ray source known. At a redshift at least this high, the most energetic gamma-rays detected in archival results from this blazar are expected to be strongly absorbed by interactions with the extragalactic background...

96. Multi-Messenger Tests of the IceCube Excess

Markus Ahlers

29/08/2013, 17:18

The IceCube Collaboration has recently reported evidence for an extraterrestrial neutrino flux. The flux is consistent with an isotropic diffuse emission which favors an extragalactic origin. However, it is not yet possible to rule out a quasi-diffuse or sub-dominant emission from multiple high-latitude or extended Galactic sources. I discuss the implications of gamma-ray observations for...

70. Secondary photons and neutrinos from distant blazars and the intergalactic magnetic fields

Warren Essey

29/08/2013, 17:42

Secondary photons and neutrinos produced in the interactions of cosmic ray protons and gamma rays emitted by distant Active Galactic Nuclei (AGN) with the photon background along the line of sight can reveal a wealth of new information about the intergalactic magnetic fields (IGMF), extragalactic background light (EBL), and the acceleration mechanisms of cosmic rays. The secondary photons...

71. Long-term Optical Study of Extragalactic TeV sources

Omar Kurtanidze

29/08/2013, 18:06

About forty (Mrk 421, Mrk 501, 1ES 1959+650 end others) northern TeV extragalactic sources have been discovered during last two decades. Most of them (2/3) we are monitoring in Abastumani Observatory from the beginning of 1997 using 125-cm and 70-cm meniscus telescopes. All observations (over 2500 nights) have been conducted with Apogee Ap6E and SBIG ST-6 CCD cameras in BVRI bands. The densest...