Detectability of Pair Echoes from Gamma-Ray Bursts and Intergalactic Magnetic Fields

Takahashi, Keitaro; Murase, Kohta; Ichiki, Kiyotomo; Inoue, Susumu; Nagataki, Shigehiro

doi:10.1086/593118

Cited by 50 publications

(55 citation statements)

References 47 publications

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“…The required filling factor of the magnetic field is about 60% (Dolag et al 2011). Other potential effects of a magnetic field in voids on the electromagnetic cascades have also been investigated, including extended emission around gamma-ray point-like sources (Aharonian et al 1994;Neronov & Semikoz 2007;Dolag et al 2009;Elyiv et al 2009;Neronov et al 2010a) and the delayed echoes of multi-TeV gamma-ray flares or gamma-ray bursts (Plaga 1995;Takahashi et al 2008;Murase et al 2008;Murase 2009). …”

Section: Introductionmentioning

confidence: 99%

Relaxation of Blazar-Induced Pair Beams in Cosmic Voids

Miniati

Elyiv

2013

ApJ

141

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The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.

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Section: Introductionmentioning

confidence: 99%

Relaxation of Blazar-Induced Pair Beams in Cosmic Voids

Miniati

Elyiv

2013

ApJ

141

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“…In this context, a method that is sensitive to weak IGMFs utilizing delayed secondary emission from high-energy gamma-ray sources was proposed by Plaga (1995) and subsequently developed by many authors (Dai et al 2002;Razzaque et al 2004;Murase et al 2007Murase et al , 2008Ichiki et al 2008;Takahashi et al 2008Takahashi et al , 2011Elyiv et al 2009;). Such emission that we refer to as "pair echos" is expected to occur typically at GeV energies, for which the Fermi Large Area Telescope (LAT) is currently the most sensitive instrument.…”

Section: Introductionmentioning

confidence: 99%

LOWER BOUNDS ON MAGNETIC FIELDS IN INTERGALACTIC VOIDS FROM LONG-TERM GeV-TeV LIGHT CURVES OF THE BLAZAR MRK 421

Takahashi

Mori

Ichiki

et al. 2013

ApJ

Self Cite

100

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Lower bounds are derived on the amplitude B of intergalactic magnetic fields (IGMFs) in the region between Galaxy and the blazar Mrk 421, from constraints on the delayed GeV pair-echo flux that are emitted by secondary e − e + produced in γ γ interactions between primary TeV gamma rays and the cosmic infrared background. The distribution of galaxies mapped by the Sloan Digital Sky Survey shows that this region is dominated by a large intergalactic void. We utilize data from long-term, simultaneous GeV-TeV observations by the Fermi Large Area Telescope and the ARGO-YBJ experiment extending over 850 days. For an assumed value of B, we evaluate the daily GeV pair-echo flux expected from the TeV data, select the dates where this exceeds the Fermi 2σ sensitivity, compute the probability that this flux is excluded by the Fermi data for each date, and then combine the probabilities using the inverse normal method. Consequently, we exclude B < 10 −20.5 G for a field coherence length of 1 kpc at ∼4σ level, as long as plasma instabilities are unimportant for cooling of the pair beam. This is much more significant than the 2σ bounds we obtained previously from observations of Mrk 501, by virtue of more extensive data from the ARGO-YBJ, as well as improved statistical analysis. Compared with most other studies of IGMF bounds, the evidence we present here for a non-zero IGMF is more robust as it does not rely on unproven assumptions on the primary TeV emission during unobserved periods.

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“…Under the assumption of a certain EBL model and intrinsic source spectrum, the nonobservation of the cascade component at GeV energies with the Fermi Large Area Telescope (LAT) led to a lower limit of  -B 10 G 16 for l = 1 Mpc (Neronov & Vovk 2010;Tavecchio et al 2011), or conversely a lower limit on the filling factor of the IGMF along the line of sight (Dolag et al 2011). Additionally, the IGMF induces a time delay of the cascade emission compared to the primary source emission (Plaga 1995;Dai et al 2002;Murase et al 2008;Takahashi et al 2008;. If this is taken into account, together with conservative assumptions on the AGN γ-ray activity, the limit is relaxed by several orders of magnitude,  -B 10 G 19 , as derived from semianalytical models (Dermer et al 2011;Huan et al 2011;Finke et al 2015) and full Monte Carlo simulations for simultaneous observations with imaging air Cherenkov telescopes (IACTs) and the Fermi LAT, leading to  -B 10 G 17 (Taylor et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the Cherenkov Telescope Array to the Detection of Intergalactic Magnetic Fields

Meyer

Conrad

Dickinson

2016

ApJ

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Very high energy (VHE; energy E100 GeV) γ-rays originating from extragalactic sources undergo pair production with low-energy photons of background radiation fields. These pairs can inverse-Compton-scatter background photons, initiating an electromagnetic cascade. The spatial and temporal structure of this secondary γ-ray signal is altered as the + -e e pairs are deflected in an intergalactic magnetic field (IGMF). We investigate how VHE observations with the future Cherenkov Telescope Array, with its high angular resolution and broad energy range, can potentially probe the IGMF. We identify promising sources and simulate γ-ray spectra over a wide range of values of the IGMF strength and coherence length using the publicly available ELMAG MonteCarlo code. Combining simulated observations in a joint likelihood approach, we find that current limits on the IGMF can be significantly improved. The projected sensitivity depends strongly on the time a source has been γ-ray active and on the emitted maximum γ-ray energy.

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Detectability of Pair Echoes from Gamma-Ray Bursts and Intergalactic Magnetic Fields

Cited by 50 publications

References 47 publications

Relaxation of Blazar-Induced Pair Beams in Cosmic Voids

Relaxation of Blazar-Induced Pair Beams in Cosmic Voids

LOWER BOUNDS ON MAGNETIC FIELDS IN INTERGALACTIC VOIDS FROM LONG-TERM GeV-TeV LIGHT CURVES OF THE BLAZAR MRK 421

Sensitivity of the Cherenkov Telescope Array to the Detection of Intergalactic Magnetic Fields

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