TP-35

Early X-ray/UV Line Signatures of GRB Progenitors and Hypernovae

P. Meszaros (1,2), C. Weth (1,3), T. Kallman (4), M. J. Rees (5)

1) Penn State University
2) Caltech
3) Uiversity of Tuebingen, Germany
4) NASA-Goddard
5) University of Cambridge

We calculate the X-ray/UV spectral line signatures expected from the interaction of a gamma-ray burst afterglow and a dense pre-burst environment produced by the progenitor. We calculate the conditions under which Fe line and edge equivalent widths of $\sim$ 1 keV can arise, and discuss the possibility of gaining information about possible progenitor scenarios using X-ray metal line spectra in the first few days of a burst. A wind or supernova remnant around the burst could produce an X-ray emission line spectrum, as well as X-ray absorption, while a hypernova funnel model would produce mainly emission lines. A detectable solar composition wind would require more mass and would produce stronger 0.5-2 keV absorption lines than a metal-enriched supernova remnant. The bound-free Fe edge equivalent widths are predicted to peak later and may be easier to detect than the Fe K-$\alpha$ line in shell models, while the opposite holds for hypernova models.