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Register a new userImproved limit on axion-like particles from gamma-ray data on Perseus cluster
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Coupling of axion-like particles (ALPs) to photons in the presence of background magnetic field affects propagation of gamma-rays through magnetized environments. This results in modification in the gamma-ray spectra of sources in or behind galaxy clusters. We search for the ALP induced effects in the Fermi/LAT and MAGIC telescope spectra of the radio galaxy NGC 1275 embedded in Perseus galaxy cluster. We report an order-of-magnitude improved upper limit on the ALP-photon coupling constant in the 0.1-10 neV mass range from non-detection of the ALP imprints on the gamma-ray spectra. The improved upper limit extends into the coupling range in which the ALP particles could form the dark matter. We estimate the sensitivity improvements for the ALP search achievable with extension of the measurements to lower and higher energies with e-ASTROGAM and CTA and show that the gamma-ray probe of ALPs with masses in $10^{-11}-10^{-7}$ eV range will be have order-of-magnitude better sensitivity compared to ground-based experiment IAXO.
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We use the first observation of Betelgeuse in hard $X$-rays to perform a novel search for axion-like particles (ALPs). Betelgeuse is not expected to be a standard source of $X$-rays, but light ALPs produced in the stellar core could be converted back into photons in the Galactic magnetic field, producing a detectable flux that peaks in the hard $X$-ray band ($E_gamma>10mathrm{,keV}$). Using a 50 ks observation of Betelgeuse by the $NuSTAR$ satellite telescope, we find no significant excess of events above the expected background. Using models of the regular Galactic magnetic field in the direction of Betelgeuse, we set a 95% C.L. upper limit on the ALP-photon coupling of ${g_{agamma}<(0.5-1.8)times10^{-11}}$ GeV$^{-1}$ (depending on magnetic field model) for ALP masses ${m_{a}<(5.5-3.5) times10^{-11}}$ eV.
Dark Matter (DM) may be comprised of axion-like particles (ALPs) with couplings to photons and the standard model fermions. In this paper we study photon signals arising from cosmic ray (CR) electron scattering on background ALPs. For a range of masses we find that these bounds can place competitive new constraints on the ALP-electron coupling, although in many models lifetime constraints may supersede these bounds. In addition to current Fermi constraints, we also consider future e-Astrogram bounds which will have greater sensitivity to ALP-CR induced gamma-rays.
Axion-like particles (ALPs) provide a feasible explanation for the observed low TeV opacity of the Universe. If the low TeV opacity is caused by ALP, then the $>{rm TeV}$ fluxes of unresolved extragalactic point sources will be correspondingly enhanced, resulting in an enhancement of the observed EGB spectrum at high energies. In this work, we for the first time investigate the ALP effect on the EGB spectrum. Our results show that the existence of ALPs can cause the EGB spectrum to deviate from a pure EBL absorption case. The deviation occurs at about $sim$1 TeV and current EGB measurements by Fermi-LAT cannot identify such an effect. The observation from forthcoming VHE instruments like LHAASO and CTA may be useful for studying this effect. We find that although most of the sensitive ALP parameters have been ruled out by existing ALP results, some unrestricted parameters could be probed with the EGB observation around 10 TeV.
Axion-Like Particles (ALPs) are predicted by many extensions of the Standard Model and give rise to characteristic dimming and polarization effects in a light beam travelling in a magnetic field. In this Letter, we demonstrate that photon-ALP mixing in cosmic magnetic fields produces an observable distortion in the energy spectra of distant gamma-ray sources (like AGN) for ranges of the ALP parameters allowed by all available constraints. The resulting effect is expected to show up in the energy band 100 MeV - 100 GeV, and so it can be serched with the upcoming GLAST mission.
Axion-like-particles (ALPs) emitted from the core of a magnetar can convert to photons in its magnetosphere. The resulting photon flux is sensitive to the product of $(i)$ the ALP-nucleon coupling $G_{an}$ which controls the production cross section in the core and $(ii)$ the ALP-photon coupling $g_{agamma gamma}$ which controls the conversion in the magnetosphere. We study such emissions in the soft-gamma-ray range (300 keV to 1 MeV), where the ALP spectrum peaks and astrophysical backgrounds from resonant Compton upscattering are expected to be suppressed. Using published quiescent soft-gamma-ray flux upper limits in 5 magnetars obtained with $CGRO$ COMPTEL and $INTEGRAL$ SPI/IBIS/ISGRI, we put limits on the product of the ALP-nucleon and ALP-photon couplings. We also provide a detailed study of the dependence of our results on the magnetar core temperature. We further show projections of our result for future $Fermi$-GBM observations. Our results motivate a program of studying quiescent soft-gamma-ray emission from magnetars with the $Fermi$-GBM.
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