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Title: Signatures of axion-like particles in the spectra of TeV gamma-ray sources

Abstract

No abstract prepared.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
910490
Report Number(s):
FERMILAB-PUB-07-082-A
Journal ID: ISSN 0556-2821; PRVDAQ; arXiv eprint number arXiv:0704.3044; TRN: US200724%%199
DOE Contract Number:
AC02-07CH11359
Resource Type:
Journal Article
Resource Relation:
Journal Name: Phys.Rev.D76:023001,2007; Journal Volume: 76
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS, 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; SPECTRA; GAMMA SOURCES; FERMILAB; Astrophysics, Phenomenology-HEP

Citation Formats

Mirizzi, Alessandro, /Munich, Max Planck Inst. /Bari U. /INFN, Bari, Raffelt, Georg G., /Munich, Max Planck Inst., Serpico, Pasquale D., and /Fermilab. Signatures of axion-like particles in the spectra of TeV gamma-ray sources. United States: N. p., 2007. Web. doi:10.1103/PhysRevD.76.023001.
Mirizzi, Alessandro, /Munich, Max Planck Inst. /Bari U. /INFN, Bari, Raffelt, Georg G., /Munich, Max Planck Inst., Serpico, Pasquale D., & /Fermilab. Signatures of axion-like particles in the spectra of TeV gamma-ray sources. United States. doi:10.1103/PhysRevD.76.023001.
Mirizzi, Alessandro, /Munich, Max Planck Inst. /Bari U. /INFN, Bari, Raffelt, Georg G., /Munich, Max Planck Inst., Serpico, Pasquale D., and /Fermilab. Sun . "Signatures of axion-like particles in the spectra of TeV gamma-ray sources". United States. doi:10.1103/PhysRevD.76.023001. https://www.osti.gov/servlets/purl/910490.
@article{osti_910490,
title = {Signatures of axion-like particles in the spectra of TeV gamma-ray sources},
author = {Mirizzi, Alessandro and /Munich, Max Planck Inst. /Bari U. /INFN, Bari and Raffelt, Georg G. and /Munich, Max Planck Inst. and Serpico, Pasquale D. and /Fermilab},
abstractNote = {No abstract prepared.},
doi = {10.1103/PhysRevD.76.023001},
journal = {Phys.Rev.D76:023001,2007},
number = ,
volume = 76,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}
  • Axion Like Particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in amore » decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN source being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at z=0.444) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the EBL intensity at 3.6 {micro}m (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at z=0.1-0.2. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and imaging atmospheric Cherenkov telescopes like CANGAROO, HESS, MAGIC and VERITAS.« less
  • Photons couple to Axion-Like Particles (ALPs) or more generally to any pseudo Nambu-Goldstone boson in the presence of an external electromagnetic field. Mixing between photons and ALPs in the strong magnetic field of a Gamma-Ray Burst (GRB) jet during the prompt emission phase can leave observable imprints on the gamma-ray polarization and spectrum. Mixing in the intergalactic medium is not expected to modify these signatures for ALP mass > 10{sup −14} eV and/or for < nG magnetic field. We show that the depletion of photons due to conversion to ALPs changes the linear degree of polarization from the values predictedmore » by the synchrotron model of gamma ray emission. We also show that when the magnetic field orientation in the propagation region is perpendicular to the field orientation in the production region, the observed synchrotron spectrum becomes steeper than the theoretical prediction and as detected in a sizable fraction of GRB sample. Detection of the correlated polarization and spectral signatures from these steep-spectrum GRBs by gamma-ray polarimeters can be a very powerful probe to discover ALPs. Measurement of gamma-ray polarization from GRBs in general, with high statistics, can also be useful to search for ALPs.« less
  • We extend previous searches for X-ray spectral modulations induced by ALP-photon conversion to a variety of new sources, all consisting of quasars or AGNs located in or behind galaxy clusters. We consider a total of seven new sources, with data drawn from the Chandra archive. In all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the ALP-photon coupling parameter g {sub a} {sub γγ}. Two sources are particularly good: the Seyfert galaxy 2E3140 in A1795 and the AGN NGC3862 within the cluster A1367, leading to 95%more » bounds for light ALPs ( m {sub a} ∼< 10{sup −12} eV) of g {sub a} {sub γγ} ∼< 1.5 × 10{sup −12} GeV{sup −1} and g {sub a} {sub γγ} ∼< 2.4 × 10{sup −12} GeV{sup −1} respectively.« less
  • We revise the bound from the supernova SN1987A on the coupling of ultralight axion-like particles (ALPs) to photons. In a core-collapse supernova, ALPs would be emitted via the Primakoff process, and eventually convert into gamma rays in the magnetic field of the Milky Way. The lack of a gamma-ray signal in the GRS instrument of the SMM satellite in coincidence with the observation of the neutrinos emitted from SN1987A therefore provides a strong bound on their coupling to photons. Due to the large uncertainty associated with the current bound, we revise this argument, based on state-of-the-art physical inputs both formore » the supernova models and for the Milky-Way magnetic field. Furthermore, we provide major amendments, such as the consistent treatment of nucleon-degeneracy effects and of the reduction of the nuclear masses in the hot and dense nuclear medium of the supernova. With these improvements, we obtain a new upper limit on the photon-ALP coupling: g{sub aγ} ∼< 5.3 × 10{sup -12} GeV{sup -1}, for m{sub a} ∼< 4.4 × 10{sup -10} eV, and we also give its dependence at larger ALP masses m{sub a}. Moreover, we discuss how much the Fermi-LAT satellite experiment could improve this bound, should a close-enough supernova explode in the near future.« less
  • Extensions of the Standard Model of particles commonly predict the existence of axion(-like) particles (ALPs) that could be detected through their coupling to photons in external magnetic fields. This coupling could lead to modifications of γ-ray spectra from extragalactic sources. Above a certain energy, the γ-ray flux should be exponentially damped due to the interaction with photons of background radiations fields. ALPs, on the other hand, propagate unimpeded over cosmological distances and a reconversion into γ-rays could lead to an additional component in the spectra. Here, we present the sensitivity of the proposed Cherenkov Telescope Array (CTA) to detect thismore » spectral hardening. Using the full instrumental response functions of CTA, a combined likelihood analysis of four γ-ray sources shows that a significant detection of the ALP signal is possible for couplings g{sub aγ} ≳ 2 × 10{sup −11} GeV{sup −1} and ALP masses m{sub a} ∼< 100 neV. We discuss the dependency of these values on different model assumptions and magnetic-field scenarios and identify the best observation strategy to search for an ALP induced boost of the γ-ray flux.« less