Passage of a Gamma-Ray Burst Through a Molecular Cloud: Cloud Ionization Structure

Abstract

The model is constructed of the propagation of gamma-ray burst radiation through a dense molecular cloud. The main processes of the interaction of the radiation with the interstellar gas are taken into account in the simulations: the ionization of H and He atoms, the ionization of metal ions and the emission of Auger electrons, the photoionization and the photodissociation of H${}_2$ molecules, the absorption of ultraviolet radiation via Lyman and Werner band transitions of H${}_2$, the thermal sublimation of dust grains. The ionization of metal ions by X-ray radiation determines the gas ionization fraction in the cloud region, where the gas is predominantly neutral. The ionization of inner electron shells of ions is accompanied by the emission of Auger electrons, giving rise to metal ions in a high ionization state. In particular, the column densities of Mg, Si, Fe in the ionization states I$-$IV are much lower than the column densities of these ions in the ionization state V and higher. The photoionization of metal ions by ultraviolet radiation takes place at distances smaller than the dust-destruction radius and only for neutral atoms with an ionization threshold below 13.6 eV. The simulations have confirmed the previously made suggestion that the ionization of He atoms plays an important role in the absorption of radiation in the X-ray wavelength range. For a low metallicity, $[M/H]\le -1$, the role of He atoms is dominant.

22 pages, 8 figures, translation from Russian by author

References in corpus (11)

• The Physics of Gamma-Ray Bursts and Relativistic Jets
• GRB Radiative Efficiencies Derived from the Swift Data: GRBs vs. XRFs, Long vs. Short
• Gamma Ray Bursts Are Observed Off-Axis
• Very different X-ray to optical column density ratios in gamma-ray burst afterglows: ionisation in GRB environments
• High-Ion Absorption in Seven GRB Host Galaxies at z=2-4: Evidence for both Circumburst Plasma and Outflowing Interstellar Gas
• A Survey for NV Absorption at z~z_GRB in GRB Afterglow Spectra: Clues to Gas Near the Progenitor Star
• Electrons' energy in GRB afterglows implied by radio peaks
• Unveiling the Secrets of Metallicity and Massive Star Formation Using DLAs along Gamma-ray Bursts
• Clustering of LAT light curves: a clue to the origin of high-energy emission in Gamma-Ray Bursts
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. II. Waiting mode bursts simultaneously detected by Swift/BAT
• Exceptionally bright optical emission from a rare and distant $\gamma -$ray burst

Cited by in corpus (2)

• Passage of a Gamma-Ray Burst Through a Molecular Cloud: The Absorption of its Afterglow in the X-ray Wavelength Range
• Numerical model of fast electron energy deposition in interstellar molecular gas