An Observed Correlation Between Thermal and Non-Thermal Emission in Gamma-Ray Bursts

Abstract

Recent observations by the $Fermi$ Gamma-ray Space Telescope have confirmed the existence of thermal and non-thermal components in the prompt photon spectra of some Gamma-ray bursts (GRBs). Through an analysis of six bright Fermi GRBs, we have discovered a correlation between the observed photospheric and non-thermal $\gamma$-ray emission components of several GRBs using a physical model that has previously been shown to be a good fit to the Fermi data. From the spectral parameters of these fits we find that the characteristic energies, $E_{\mathrm{p}}$ and $kT$, of these two components are correlated via the relation $E_{\mathrm{p}}\propto T^{\alpha }$ which varies from GRB to GRB. We present an interpretation in which the value of index $\alpha$ indicates whether the jet is dominated by kinetic or magnetic energy. To date, this jet composition parameter has been assumed in the modeling of GRB outflows rather than derived from the data.

References in corpus (7)

• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724B
• A Comprehensive Analysis of Fermi Gamma-Ray Burst Data. I. Spectral Components and Their Possible Physical Origins of LAT/GBM GRBs
• GRB110721A: An extreme peak energy and signatures of the photosphere
• Quasi-blackbody component and radiative efficiency of the prompt emission of gamma-ray bursts
• A new method of determining the initial size and Lorentz factor of gamma-ray burst fireballs using a thermal emission component
• The photospheric radiation model for the prompt emission of Gamma-ray Bursts: Interpreting four observed correlations

Cited by in corpus (12)

• The Physics of Gamma-Ray Bursts and Relativistic Jets
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: 10 Years of Data
• Photosphere emission in the X-Ray Flares of Swift Gamma-Ray Bursts and Implications for the Fireball Properties
• On the $\alpha$-Intensity Correlation in Gamma-Ray Bursts: Subphotospheric Heating with Varying Entropy
• Ultra-high Energy Cosmic Rays and Neutrinos from Gamma-Ray Bursts, Hypernovae and Galactic Shocks
• Testing a model for subphotospheric dissipation in GRBs: fits to Fermi data constrain the dissipation scenario
• Constraining the bulk Lorentz factor from the photosphere emission
• One Fits All: A Unified Synchrotron Model Explains GRBs with FRED-Shaped Pulses
• Statistical properties of Fermi GBM GRBs' spectra
• A comprehensive view of blackbody components in the X-ray spectra of GRBs
• Broadening of the thermal component of the prompt GRB emission due to rapid temperature evolution
• A Comprehensive Study of Bright Fermi-GBM Short Gamma-Ray Bursts: II. Very Short Burst and Its Implications