Temporal Evolution of Pair Attenuation Signatures in Gamma-Ray Burst Spectra

Abstract

The spectra obtained above 100 MeV by the EGRET experiment aboard the Compton Gamma-Ray Observatory for a handful of gamma-ray bursts has given no indication of any spectral attenuation that might preclude detection of bursts at higher energies. With the discovery of optical afterglows and counterparts to bursts in the last few years, enabling the determination of significant redshifts for these sources, it is anticipated that profound spectral attenuation will arise in the Gamma-Ray Large Area Space Telescope (GLAST) energy band of 30 MeV-300 GeV for many if not most bursts. This paper explores time-dependent expectations for burst spectral properties in the EGRET/GLAST band, focusing on how attenuation of photons by pair creation internal to the source generates distinctive spectral signatures. The energy of spectral breaks and the associated spectral indices provide valuable information that constrains the bulk Lorentz factor of the GRB outflow at a given time. Moreover, the distinct temporal behavior that is present for internal attenuation is easily distinguished from extrinsic absorption due to intervening cosmic background fields. These characteristics define palpable observational goals for both spaced-based hard gamma-ray experiments such as GLAST, and ground-based Cherenkov telescopes, and strongly impact the observability of bursts above 300 MeV.

16 pages, 5 embedded figures, apjgalley format, To appear in The Astrophysical Journal, Vol 649, October 1, 2006 issue

References in corpus (3)

• Gamma-Ray Bursts in the Swift Era
• Discovery of VHE gamma-ray emission from 1ES1218+30.4
• Flux upper limit of gamma-ray emission by GRB050713a from MAGIC Telescope observations

Cited by in corpus (41)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Gamma-Ray Bursts in the Swift Era
• Insights Into the High-Energy Gamma-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era
• Detection of a spectral break in the extra hard component of GRB 090926A
• Prompt high-energy emission from gamma-ray bursts in the internal shock model
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: 10 Years of Data
• Gamma Ray Bursts
• Opacity Build-up in Impulsive Relativistic Sources
• The Role of Stochastic Acceleration in the Prompt Emission of Gamma-Ray Bursts: Application to Hadronic Injection
• Gamma-Ray Burst Science in the Era of the Cherenkov Telescope Array
• Prompt GeV-TeV Emission of Gamma-Ray Bursts Due to High-Energy Protons, Muons and Electron-Positron Pairs
• High-Energy Multi-Messenger Transient Astrophysics
• High energy neutrino flux from individual blazar flares
• Fermi observations of high-energy gamma-ray emission from GRB 080825C
• Prospects for GRB Science with the Fermi Large Area Telescope
• Probing the Nature of the Weakest Intergalactic Magnetic Fields with the High Energy Emission of Gamma-Ray Bursts
• H.E.S.S. observations of gamma-ray bursts in 2003-2007
• On the Implications of Late Internal Dissipation for Shallow-Decay Afterglow Emission and Associated High-Energy Gamma-Ray Signals
• High-energy neutrino and gamma-ray transients from trans-relativistic supernova shock breakouts
• Constraining the High-Energy Emission from Gamma-ray Bursts with Fermi
• Spectral-Temporal Simulations of Internal Dissipation Models of Gamma-Ray Bursts
• The bulk Lorentz factors of Fermi-LAT GRBs
• Prospects for Detecting Gamma-Ray Bursts at Very High Energies with the Cherenkov Telescope Array
• Diagnosing GRB Prompt Emission Site with Spectral Cut-Off Energy
• H.E.S.S. Observations of the Prompt and Afterglow Phases of GRB 060602B
• High-energy emission as a test of the prior emission model for gamma-ray burst afterglows
• Gamma Ray Bursts
• Correlation of Photon and Neutrino Fluxes in Blazars and Gamma Ray Bursts
• IACT observations of gamma-ray bursts: prospects for the Cherenkov Telescope Array
• Closure Relations for Electron-Positron Pair-Signatures in Gamma-Ray Bursts
• GRB 221009A: A light dark matter burst or an extremely bright Inverse Compton component?
• Can we probe the Lorentz factor of gamma-ray bursts from GeV-TeV spectra integrated over internal shocks?
• The Effect of Pair Cascades on the High-Energy Spectral Cutoff in Gamma-Ray Bursts
• Gamma Ray Burst Predictions for the Fermi Gamma Ray Space Telescope
• Time evolution of the spectral break in the high-energy extra component of GRB 090926A
• On the prospects of gamma-ray burst detection in the TeV band
• Which $E_{\mathrm{peak}}$? - The Characteristic Energy of Gamma-Ray Burst Spectra
• Using Gamma-Ray Burst Prompt Emission to Probe Relativistic Shock Acceleration
• Constraints on the very high energy gamma-ray emission from short GRBs with HAWC
• Lorentz Factor Evolution of an Expanding Jet Shell Observed in Gamma-ray Burst: Case study of GRB 160625B
• Jets in a Gamma-Ray Burst During its Prompt Emission: Evolution of Lorentz Factor