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Search Results: 1 - 10 of 198117 matches for " N. Fraija "
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Very high energy neutrino expectation from Fanaroff-Riley I sources
A. Marinelli,N. Fraija
Physics , 2014, DOI: 10.1017/S1743921315002136
Abstract: Fanaroff-Riley I radiogalaxies have been observed in TeV gamma-rays during the last decades. The origin of the emission processes related with this energy band is still under debate. Here we consider the case of the two closest Fanaroff-Riley I objects: Centaurus A and M87. Their entire broadband spectral energy distributions and variability fluxes show evidences that leptonic models are not sufficient to explain their fluxes above 100 GeV. Indeed, both objects have been imaged by LAT instrument aboard of Fermi telescope with measured spectra well connected with one-zone leptonic models. However, to explain the TeV spectra obtained with campaigns by H.E.S.S., for Centaurus A, and by VERITAS, MAGIC and H.E.S.S. for M87, different emission processes must be introduced. In this work we evoke hadronic scenarios to describe the TeV gamma-ray fluxes observed and to obtain the expected neutrino counterparts for each considered TeV campaign. With the obtained neutrino spectra we calculate, through Monte Carlo simulations, the expected neutrino event rate in a hypothetical Km$^{3}$ neutrino telescope and we compare the results with what has been observed by IceCube experiment up to now.
The Hadronic Picture of the Radiogalaxy M87
A. Marinelli,N. Fraija,B. Patricelli
Physics , 2014,
Abstract: Very high energy gamma-ray emission of Fanaroff-Riley I objects is not univocally explained by a single emission model. Leptonic models with one and multi-zone emission regions, occurring in the jet of these objects, are usually used to describe the broadband spectral energy distribution. A correlation between the X-ray and TeV emission is naturally expected within leptonic models whereas a lack of correlation between these two observables represents a challenge and favors the hadronic scenarios. This is the case of M87 as we show here by analyzing its TeV and X-ray emission recorded in the last decade. Furthermore, we point out that the spectra obtained by MAGIC, H.E.S.S. and VERITAS telescopes cannot be described with the same leptonic model introduced by the Fermi-LAT collaboration. We introduce hadronic scenarios to explain the TeV gamma-ray fluxes of this radiogalaxy as products of Fermi-accelarated protons interacting with seed photons in the jet or thermal particles in the giant lobes. By fitting this part of spectral energy distribution as pion decay products, we obtain the expected neutrino counterpart and the luminosity of accelerating protons in the jet and/or lobes. With the expected neutrino fluxes we investigate, through Monte Carlo simulations, the possibility to see the signal from M87 with a Km$^{3}$ neutrino telescope, and compare the results with what has been seen by IceCube experiment up to now. Finally we constrain the features of giant lobes through the observations performed at ultra high energies by TA experiment.
Hadronic processes as origin of TeV emission in Fanaroff-Riley Class I: Cen A, M87 and NGC1275
N. Fraija,M. M. Gonzalez,M. Perez
Physics , 2012,
Abstract: Recent detections of Fanaroff-Riley Class I AGNs by HESS, MAGIC, and VERITAS suggest that very-high-energy gamma-rays (VHE, E > 100 GeV) may not have a leptonic origin. We present a hadronic model to describe the TeV photons as the neutral pion decay resulting from pgamma and pp interactions. For the pgamma interaction, we assume that the target photons are produced by leptonic processes and apparent at the second spectral peak. For the pp interaction we consider as targets the thermal particle densities in the lobes. We show that this model can describe the TeV spectra of the radio galaxies NCG 1275, M87 and Cen A
Hadronic flares and associated neutrinos for Markarian 421
A. Marinelli,B. Patricelli,N. Fraija
Physics , 2015, DOI: 10.1017/S174392131500215X
Abstract: Markarian 421 (Mrk 421) is one of the brightest, fastest and closest BL Lac object known. Its very high energy (VHE) spectrum has been successfully modeled with both leptonic and hadronic models and not conclusive results have been achieved yet about the origin of its VHE emission. Here we investigate the possibility that a fraction of the VHE flares of Mrk 421 are due to hadronic processes and calculate the expected neutrino flux associated. We introduce the obtained neutrino flux in a Monte Carlo simulation to see the expectation for a Km$^{3}$ Cherenkov neutrino telescope.
Long and short high energy components presented in GRBs
N. Fraija,M. M. Gonzalez,R. Sacahui,W. H. Lee
Physics , 2012,
Abstract: We present a leptonic model on the external shock framework to describe the long- and short- lasting GeV component of some GRBs. This model was already applied successfully to GRB 090926A, and we extend it to describe the high-energy emission of GRB 090902B and GRB 090510. We argue that the high-energy emission consists of two components, one at MeV energies with a duration of a few seconds during the prompt phase, and a second GeV component lasting hundred of seconds after the prompt phase. The short high-energy component can be described as SSC emission from a reverse shock and the longer component arises from SSC emission of the forward shock. The main assumption of our model is that the jet is magnetized and evolves in the thick-shell case. The calculated fluxes and break energies are all consistent with the observed values.
GeV - PeV Neutrino Production and Oscillation in hidden jets from GRBs
Nissim Fraija
Physics , 2013, DOI: 10.1093/mnras/stt2036
Abstract: 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.
Could a plasma in quasi-thermal equilibrium be associated to the "orphan" TeV flares ?
Nissim Fraija
Physics , 2015, DOI: 10.1016/j.astropartphys.2015.04.007
Abstract: TeV $\gamma$-ray detections in flaring states without activity in X-rays from blazars have attracted much attention due to the irregularity of these "orphan" flares. Although the synchrotron self-Compton model has been very successful in explaining the spectral energy distribution and spectral variability of these sources, it has not been able to describe these atypical flaring events. On the other hand, an electron-positron pair plasma at the base of the AGN jet was proposed as the mechanism of bulk acceleration of relativistic outflows. This plasma in quasi-themal equilibrium called Wein fireball emits radiation at MeV-peak energies serving as target of accelerated protons. In this work we describe the "orphan" TeV flares presented in blazars 1ES 1959+650 and Mrk421 assuming geometrical considerations in the jet and evoking the interactions of Fermi-accelerated protons and MeV-peak target photons coming from the Wein fireball. After describing successfully these "orphan" TeV flares, we correlate the TeV $\gamma$-ray, neutrino and UHECR fluxes through p$\gamma$ interactions and calculate the number of high-energy neutrinos and UHECRs expected in IceCube/AMANDA and TA experiment, respectively. In addition, thermal MeV neutrinos produced mainly through electron-positron annihilation at the Wein fireball will be able to propagate through it. By considering two- (solar, atmospheric and accelerator parameters) and three-neutrino mixing, we study the resonant oscillations and estimate the neutrino flavor ratios as well as the number of thermal neutrinos expected on Earth.
GRB 110731A: Early afterglow in stellar wind powered by a magnetized outflow
Nissim Fraija
Physics , 2015, DOI: 10.1088/0004-637X/804/2/105
Abstract: One of the most energetic gamma-ray burst GRB 110731A was observed from optical to GeV energy range. Previous analysis on the prompt phase revealed similarities with the Large Area Telescope (LAT) bursts observed by Fermi: i) a delayed onset of the high-energy emission ($> 100$ MeV), ii) a short-lasting bright peak at later times and iii) a temporally extended component from this phase and lasting hundreds of seconds. Additionally to the prompt phase, multiwavelength observations over different epochs showed that the spectral energy distribution was better fitted by a wind afterglow model. We present a leptonic model based on an early afterglow that evolves in a stellar wind of its progenitor. We apply this model to interpret the temporally extended LAT emission and the brightest LAT peak exhibited by the prompt phase of GRB 110731A. Additionally, using the same set of parameters, we describe the multiwavelength afterglow observations. The origin of the temporally extended LAT, X-ray and optical flux is explained through synchrotron radiation from the forward shock and the brightest LAT peak is described evoking the synchrotron self-Compton emission from the reverse shock. The bulk Lorentz factor required in this model ($\Gamma\simeq520$) lies in the range of values demanded for most LAT-detected gamma-ray bursts. We show that the strength of the magnetic field in the reverse-shock region is $\sim$ 50 times stronger than in the forward-shock region. This result suggests that for GRB 110731A, the central engine is likely entrained with strong magnetic fields.
Propagation and neutrino oscillations in the base of a highly magnetized gamma-ray burst fireball flow
Nissim Fraija
Physics , 2014, DOI: 10.1088/0004-637X/787/2/140
Abstract: Neutrons play an important role in the dynamics of gamma-ray bursts. The presence of neutrons in the baryon-loaded fireball is expected. If the neutrons abundance is comparable to that of protons, important features may be observed such as quasi-thermal multi-GeV neutrinos in coincidence with a subphotospheric $\gamma$-ray emission, nucleosynthesis at later times and rebrightening of the afterglow emission. Additionally, thermal MeV neutrinos are created by electron-positron annihilation, electron (positron) capture on protons (neutrons) and nucleonic bremsstrahlung. Although MeV neutrinos are difficult to detect, quasi-thermal GeV neutrinos are expected in km$^3$ detectors and/or DeepCore+IceCube. In this paper, we show that neutrino oscillations have outstanding implications for the dynamics of the fireball evolution and also that they can be detected through their flavor ratio on Earth. For that we derive the resonance and charged-neutrality conditions as well as the neutrino self-energy and effective potential up to order $m_W^{-4}$ at strong, moderate and weak magnetic field approximation to constrain the dynamics of the fireball. We found important implications: i) resonant oscillations are suppressed for high baryon densities as well as neutrons abundance larger than that of protons and ii) the effect of magnetic field is to decrease the proton-to-neutron ratio aside from the number of multi-GeV neutrinos expected in DeepCore detector. Also we estimate the GeV neutrino flavor ratios along the jet and on Earth.
Gamma-ray fluxes from the core emission of Centaurus A: A puzzle solved
Nissim Fraija
Physics , 2014, DOI: 10.1093/mnras/stu652
Abstract: 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 $\alpha_1$=2.74$\pm$0.03 and $\alpha_2$=2.09$\pm$0.20, respectively. Also a faint $\gamma$-ray flux at TeV energies was detected by H.E.S.S.. In this paper we show that the spectrum at GeV-TeV energies is described through synchrotron self-Compton emission up to a few GeV ($\sim$ 4 GeV) and $\pi^0$ decay products up to TeV energies, although the emission of synchrotron radiation by muons could contribute to the spectrum at GeV energies, if they are rapidly accelerated. Muons and $\pi^0$s are generated in the interactions of accelerated protons with two populations of seed photons which were reported by Compton Gamma-Ray Observatory: one population at intermediate state emission with energy peak of 0.15 MeV and another at low state emission with energy peak of 0.59 MeV. In addition, we show that the reported observations of ultra-high-energy cosmic rays and non high-energy neutrino detection around Centaurus A can be explained through these interactions, assuming that proton spectrum is extended up to ultra-high-energies.
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