N. Fraija

OBSERVATION OF SMALL-SCALE ANISOTROPY IN THE ARRIVAL DIRECTION DISTRIBUTION OF TeV COSMIC RAYS WITH HAWC

The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic rays at TeV energies. The detector is still under construction, but data acquisition with the partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 4.9 × 1010 events recorded between 2013 June and 2014 February shows anisotropy at the 10–4 level on angular scales of about 10°. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to l = 15 contribute significantly to the excesses.

Search for Gamma-Rays from the Unusually Bright GRB 130427A with the HAWC Gamma-Ray Observatory

The first limits on the prompt emission from the long gamma-ray burst (GRB) 130427A in the >100 GeV energy band are reported. GRB 130427A was the most powerful burst ever detected with a redshift z 0.5 and featured the longest lasting emission above 100 MeV. The energy spectrum extends at least up to 95 GeV, clearly in the range observable by the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, a new extensive air shower detector currently under construction in central Mexico. The burst occurred under unfavorable observation conditions, low in the sky and when HAWC was running 10% of the final detector. Based on the observed light curve at MeV-GeV energies, eight different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith would be easily detected by the full HAWC detector, which will be completed soon. The detection rate of the full HAWC detector may be as high as one to two GRBs per year. A detection could provide important information regarding the high energy processes at work and the observation of a possible cut-off beyond the Fermi Large Area Telescope energy range could be the signature of gamma-ray absorption, either in the GRB or along the line of sight due to the extragalactic background light.

GeV–PeV neutrino production and oscillation in hidden jets from gamma-ray bursts

Long gamma-ray bursts have been widely associated with collapsing massive stars in the framework of collapsar model. High-energy neutrinos and photons can be produced in the internal shocks of middle relativistic jets from core-collapse supernova. Although photons can hardly escape, high-energy neutrinos could be the only signature when the jets are hidden. We show that using suitable parameters, high-energy neutrinos in GeV - PeV range can be produced in the hidden jet inside the collapsar, thus demonstrating that these objects are candidates to produce neutrinos with energies between 1 - 10 PeV which were observed with IceCube. On the other hand, due to matter effects, high-energy neutrinos may oscillate resonantly from one flavor to another before leaving the star. Using two (solar, atmospheric and accelerator parameters) and three neutrino mixing, we study the possibility of resonant oscillation for these neutrinos created in internal shocks. Also we compute the probabilities of neutrino oscillations in the matter at different distances along the jet (before leaving the star) and after in vacuum, on their path to Earth. Finally, neutrino flavor ratios on Earth are estimated.

Search for TeV Gamma-Ray Emission from Point-like Sources in the Inner Galactic Plane with a Partial Configuration of the HAWC Observatory

Author(s): Abeysekara, AU; Alfaro, R; Alvarez, C; Alvarez, JD; Arceo, R; Arteaga-Vela Zquez, JC; Solares, HAA; Barber, AS; Baughman, BM; Bautista-Elivar, N; Reyes, ADB; Belmont, E; Benzvi, SY; Bernal, A; Braun, J; Caballero-Mora, KS; Capistran, T; Carraminana, A; Casanova, S; Castillo, M; Cotti, U; Cotzomi, J; Leon, SCD; Fuente, EDL; Leon, CD; Deyoung, T; Diaz Hernandez, R; Dingus, BL; Duvernois, MA; Ellsworth, RW; Enriquez-Rivera, O; Fiorino, DW; Fraija, N; Garfias, F; Gonzalez, MM; Goodman, JA; Gussert, M; Hampel-Arias, Z; Harding, JP; Hernandez, S; Huntemeyer, P; Hui, CM; Imran, A; Iriarte, A; Karn, P; Kieda, D; Lara, A; Lauer, RJ; Lee, WH; Lennarz, D; Vargas, HL; Linnemann, JT; Longo, M; Raya, GL; Malone, K; Marinelli, A; Marinelli, SS; Martinez, H; Martinez, O; Martinez-Castro, J; Matthews, JA; Miranda-Romagnoli, P; Moreno, E; Mostafa, M; Nellen, L; Newbold, M; Noriega-Papaqui, R; Patricelli, B; Pelayo, R; Perez-Perez, EG; Pretz, J; Ren, Z; Riviere, C; Rosa-Gonzalez, D; Salazar, H; Greus, FS; Sandoval, A; Schneider, M; Sinnis, G; Smith, AJ; Woodle, KS; Springer, RW; Taboada, I; Tibolla, O; Tollefson, K | Abstract:

CORRELATION OF γ-RAY AND HIGH-ENERGY COSMIC RAY FLUXES FROM THE GIANT LOBES OF CENTAURUS A

The spectral energy distribution of giant lobes shows one main peak detected by the Wilkinson Microwave Anisotropy Probe at the low energy of 10?5?eV and a faint ?-ray flux imaged by the Fermi Large Area Telescope at an energy of ?100?MeV. On the other hand, the Pierre Auger Observatory associated some ultra-high-energy cosmic rays with the direction of Centaurus A and IceCube reported 28 neutrino-induced events in a TeV-PeV energy range, although none of them related with this direction. In this work, we describe the spectra for each of the lobes, the main peak with synchrotron radiation, and the high-energy emission with p-p interactions. After obtaining a good description of the main peak, we deduce the magnetic fields, electron densities, and the age of the lobes. Successfully describing the ?-ray emission by p-p interactions and considering thermal particles in the lobes with density in the range 10?10-10?4 cm?3 as targets, we calculate the number of ultra-high-energy cosmic rays. Although the ?-spectrum is well described with any density in the range, only when 10?4 cm?3 is considered are the expected number of events very similar to that observed by the Pierre Auger Observatory, otherwise we obtain an excessive luminosity. In addition, correlating the ?-ray and neutrino fluxes through p-p interactions, we calculate the number of high-energy neutrinos expected in IceCube. Our analysis indicates that neutrinos above 1 TeV cannot be produced in the lobes of Centaurus A, which is consistent with the results recently published by the IceCube Collaboration.

Hadronic-Origin TeV -Rays and Ultra-High Energy Cosmic Rays from Centaurus A

Centaurus A (Cen A) is the nearest radio-loud AGN and is detected from radio to very high energy gamma-rays. Its nuclear spectral energy distribution (SED) shows a double-peak feature, which is well explained by the leptonic synchrotron + synchrotron self-Compton model. This model however cannot account for the observed high energy photons in the TeV range, which display a distinct component. Here we show that ~ TeV photons can be well interpreted as the neutral pion decay products from p-gamma interactions of Fermi accelerated high energy protons in the jet with the seed photons around the second SED peak at ~170 keV. Extrapolating the inferred proton spectrum to high energies, we find that this same model is consistent with the detection of 2 ultra-high-energy cosmic ray events detected by Pierre Auger Observatory from the direction of Cen A. We also estimate the GeV neutrino flux from the same process, and find that it is too faint to be detected by current high-energy neutrino detectors.

Gamma-ray fluxes from the core emission of Centaurus A: a puzzle solved

A high-energy component in the radio galaxy Centaurus A was reported after analyzing four years of Fermi data. The spectrum of this component is described by means of a broken power law with a break energy of 4 GeV and, below and above spectral indices of

Propagation and Neutrino Oscillations in the Base of a Highly Magnetized Gamma-Ray Burst Fireball Flow

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GRB 110731A: Early Afterglow in Stellar Wind Powered By a Magnetized Outflow

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Signatures of neutrino cooling in the SN1987A scenario

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