Gamma-ray emission from the impulsive phase of the 2017 September 06 X9.3 flare

Abstract

We report hard X-ray and gamma-ray observations of the impulsive phase of the SOL2017-09-06T11:55 X9.3 solar flare. We focus on a high-energy part of the spectrum, >100 keV, and perform time resolved spectral analysis for a portion of the impulsive phase, recorded by the Konus-Wind experiment, that displayed prominent gamma-ray emission. Given a variety of possible emission components contributing to the gamma-ray emission, we employ a Bayesian inference to build the most probable fitting model. The analysis confidently revealed contributions from nuclear deexcitation lines, electron-positron annihilation line at 511 keV, and a neutron capture line at 2.223 MeV along with two components of the bremsstrahlung continuum. The revealed time evolution of the spectral components is particularly interesting. The low-energy bremsstrahlung continuum shows a soft-hard-soft pattern typical for impulsive flares, while the high-energy one shows a persistent hardening at the course of the flare. The neutron capture line emission shows an unusually short time delay relative to the nuclear deexcitation line component, which implies that the production of neutrons was significantly reduced soon after the event onset. This in turn may imply a prominent softening of the accelerated proton spectrum at the course of the flare, similar to the observed softening of the low-energy component of the accelerated electrons responsible for the low-energy bremsstrahlung continuum. We discuss possible physical scenarios, which might result in the obtained relationships between these gamma-ray components.

arXiv commentAccepted for publication in ApJ

References in corpus (18)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• Bayes in the sky: Bayesian inference and model selection in cosmology
• Statistics: Handle with Care, Detecting Multiple Model Components with the Likelihood Ratio Test
• Fermi Large Area Telescope Bright Gamma-ray Source List
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare
• Properties of Energetic Ions in the Solar Atmosphere from γ -Ray and Neutron Observations
• Analysis of Energy Spectra with Low Photon Counts via Bayesian Posterior Simulation
• Eruption of a multi-flux-rope system in solar active region 12673 leading to the two largest flares in Solar Cycle 24
• Statistical Properties of Super-hot Solar Flares
• Fermi Detection of γ-ray emission from the M2 Soft X-ray Flare on 2010 June 12
• Fermi-LAT observations of the 2017 September 10${}^{th}$ solar flare
• Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017
• Roles of photospheric motions and flux emergence in the major solar eruption on 2017 September 6
• Statistics of "Cold" Early Impulsive Solar Flares in X-ray and Microwave domains
• Konus-Wind and Helicon-Coronas-F Observations of Solar Flares
• CORONAS-F observation of gamma-ray emission from the solar flare on 2003 October 29

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