X-ray spectral diagnostics of the immediate environment of GRB 991216

Free access article

Issue		A&A Volume 389, Number 3, July III 2002


Page(s)		L74 - L77
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20020852

A&A 389, L74-L77 (2002)
DOI: 10.1051/0004-6361:20020852

Letter

X-ray spectral diagnostics of the immediate environment of GRB 991216

D. R. Ballantyne¹, E. Ramirez-Ruiz¹, D. Lazzati¹ and L. Piro²

¹ Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
e-mail: drb,enrico,lazzati@ast.cam.ac.uk
² Istituto di Astrofisica Spaziale, CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italy
e-mail: piro@ias.rm.cnr.it

(Received 15 April 2002 / Accepted 6 June 2002)

Abstract
The recent report of iron line features in the afterglow of the gamma-ray burst (GRB) 991216 has important implications for the properties of the radiating material and hence the nature of the immediate burst environment. We argue that the putative strong Fe emission line can be attributed to the reflected emission from Thomson-thick matter which is illuminated by a power-law continuum. The ionization parameter of the material (i.e., the flux to density ratio) is around 10³, resulting in a Fe K $\alpha$ line from He-like iron. A supersolar abundance of iron is not required by the data. Interestingly, the ionizing continuum must be harder than the observed one. We interpret this as due to the fact that the observed continuum is dominated by the standard blast wave emission, while the line is produced by reprocessing material located at much smaller radii.

Key words: gamma rays: bursts -- X-rays: general -- radiation mechanisms: non-thermal -- line: formation

Offprint request: D. Ballantyne, drb@ast.cam.ac.uk

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.