2001/08/14 by B. T. Draine, Lei Hao · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/339394
submitted to ApJ, 27 pages, 11 figures, Latex
arxiv created 2001/08/14 · openalex publication_date 2002/04/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
A gamma-ray burst (GRB) with strong optical-UV emission occurring in a molecular cloud will photodissociate H 2 , photoionize H 2 , H, and He, and destroy dust grains. We model these processes, including time-dependent radiative transfer, in both continuum radiation and the resonance lines of H 2 . The UV will pump H 2 into vibrationally excited levels. We calculate the absorption spectrum imprinted on radiation from the GRB at various times. In addition to the strong absorption lines of v = 0 H 2 at λ < 1110 Å due to cold ambient gas, we find that radiation reaching us from the GRB and its afterglow will show strong absorption lines due to vibrationally excited H 2 at 1110 Å < λ < 1705 Å. These absorption lines, if observed, would provide unequivocal evidence for the association of the GRB with molecular gas. Low-resolution spectra will exhibit conspicuous features due to clustering of individual lines; a list of the strongest such absorption features is given for the spectral resolution R ≈ 350 characteristic of the grism on the Swift UV-optical telescope.