Modulations in Spectra of Galactic Gamma-ray sources as a result of photon-ALPs mixing.

Abstract

Axion like particles (ALPs) are fundamental pseudo scalar particles with properties similar to Axions which are a well-known extensions of the standard model to solve the strong CP problem in Quantum Chromodynamics. ALPs can oscillate into photons and vice versa in the presence of an external tranversal magnetic field. This oscillation of photon and ALPs could have important implications for astronomical observations, i.e. a characteristic energy dependent attenuation in Gamma ray spectra for astrophysical sources. Here we have revisited the opportunity to search Photon-ALPs coupling in the disappearance channel. We use eight years of Fermi Pass 8 data of a selection of promising galactic Gamma-ray source candidates and study the modulation in the spectra in accordance with Photon-ALPs mixing and estimate best fit values of the parameters i.e. Photon-ALPs coupling constant (gαγγ) and ALPs mass(mα). For the magnetic field we use large scale galactic magnetic field models based on Faraday rotation measurements and we have also studied the survival probability of photons in the Galactic plane.

Searching for spectral oscillations due to photon-axionlike particle conversion using the Fermi-LAT observations of bright supernova remnants

“…The γ-ray data have been widely used to search for ALP signals [16][17][18][19][20][21][22][23][24][25]. The Fermi Collaboration searched for ALPs from the radio galaxy NGC 1275, located in the Persus cluster, which has relatively good magnetic field measurements.…”

“…By studying modulation behaviors in spectra of 6 γ-ray pulsars, Majumdar etal. [23,24] reported intriguing indications of photon-ALP mixing. Even stronger evidence was obtained in a further analysis of 12 non-Galactic plane pulsars [25].…”

Searching for the possible signal of the photon-axionlike particle oscillation in the combined GeV and TeV spectra of supernova remnants

“…The large-scale Galactic magnetic field model developed by Jansson & Farrar [51] (Bfield1) is adopted in our work, which has been wildly used in the relevant investigations [29][30][31][32][33]. This model composes of a disk field, an extended halo field and out of plane component and provides a best fit to WMAP7 Galactic synchrotron emission map and more than 40,000 extragalactic rotation measures (RM) data.…”

“…Collaboration [23] and Zhang et al [28] without significant signal of ALPs found. The γ-ray spectra of bright pulsars [29][30][31] and SNRs [32] obtained from the Fermi-LAT data show intriguing indications for the photon-ALP oscillation, but the best-fit parameters are in tension with the limit from the CAST helioscope. Besides, Liang et al found that higher ALP mass region of the ALP parameter space can be probed by the H.E.S.S.…”

“…Besides, the conversion between γ-ray photons and ALPs in external magnetic fields could create energy-dependent modulations in spectra of γ-ray sources, which is so called the photon-ALP oscillation. Such a spectral oscillation effect could be a smoking-gun signature for the existence of ALPs [16][17][18][19][20][21] and has been widely used to search for ALP signals [22][23][24][25][26][27][28][29][30][31][32][33]. The Fermi-LAT Collaboration have searched for the photon-ALP oscillation signal in the High Energy (HE) spectrum of NGC 1275 and excluded the coupling g aγ above 5×10 −11 GeV −1 for ALP masses 0.5−5 neV [26].…”