Implications of Cosmological Gamma-Ray Absorption II. Modification of gamma-ray spectra
نویسندگان
چکیده
Bearing on the model for the time-dependent metagalactic radiation field developed in the first paper of this series, we compute the gamma-ray attenuation due to pair production in photon-photon scattering. Emphasis is on the effects of varying the star formation rate and the fraction of UV radiation assumed to escape from the star forming regions, the latter being important mainly for high-redshift sources. Conversely, we investigate how the metagalactic radiation field can be measured from the gamma-ray pair creation cutoff as a function of redshift, the Fazio-Stecker relation. For three observed TeV-blazars (Mkn501, Mkn421, H1426+428) we study the effects of gamma-ray attenuation on their spectra in detail.
منابع مشابه
Water Absorption of Chitosan, Collagen and Chitosan/Collagen Blend Membranes Exposed to Gamma-ray Irradiation
TThis study investigated the water absorption of chitosan, collagen, and chitosan/collagen blend membranes exposed to gamma-ray irradiation. These membranes were produced via the solvent evaporation method. All membranes then underwent irradiation at 15 or 25 kGy gamma-ray doses, while membranes without irradiation were used as controls. After immersing the membranes in distilled water for up t...
متن کاملTheoretical Models of Gamma-Ray Bursts
Models of gamma ray bursts are reviewed in the light of recent observations of afterglows which point towards a cosmological origin. The physics of fireball shock models is discussed, with attention to the type of light histories and spectra during the gamma-ray phase. The evolution of the remnants and their afterglows is considered, as well as their implications for our current understanding o...
متن کاملGamma-ray Bursts: Multiwaveband Spectral Predictions for Blast Wave Models
In almost any scenario for ’cosmological’ gamma-ray bursts (and in many models where they originate in our own Galaxy), the initial energy density is so large that the resulting relativistic plasma expands with v ∼ c producing a blast wave ahead of it and a reverse shock moving into the ejecta, as it ploughs into the external medium. We evaluate the radiation expected from these shocks, for bot...
متن کاملThe absorption properties of gamma-ray burst afterglows measured by BeppoSAX
We present an analysis of the X-ray absorption properties of 6 gamma-ray burst (GRB) afterglows measured with BeppoSAX. Between 8 hrs and 20 hrs after the initial GRB trigger, individual spectra can be described by a power-law with a photon index of ∼2 and absorption, NH, marginally consistent with the galactic value. Taken collectively, the data are inconsistent with zero NH at the >99.999% co...
متن کاملPair Production Absorption Troughs in Gamma-ray Burst Spectra: a Potential Distance Discriminator
In order to explain the emergence of a high-energy continuum in gamma-ray bursts (GRBs) detected by EGRET, relativistic bulk motion with large Lorentz factors has recently been inferred for these sources regardless of whether they are of galactic or cosmological origin. This conclusion results from calculations of internal pair production opacities in bursts that usually assume an infinite powe...
متن کامل