%0 Journal Article
%T X-ray Spectral Components in the Afterglow of GRB 130925A
%A Eric C. Bellm
%A Nicolas M. Barriere
%A Varun Bhalerao
%A Steven E. Boggs
%A S. Bradley Cenko
%A Finn E. Christensen
%A William W. Craig
%A Karl Forster
%A Chris L. Fryer
%A Charles J. Hailey
%A Fiona A. Harrison
%A Assaf Horesh
%A Chryssa Kouveliotou
%A Kristin K. Madsen
%A Jon M. Miller
%A Eran O. Ofek
%A Daniel A. Perley
%A Vikram R. Rana
%A Stephen P. Reynolds
%A Daniel Stern
%A John A. Tomsick
%A William W. Zhang
%J Physics
%D 2014
%I arXiv
%R 10.1088/2041-8205/784/2/L19
%X We have identified spectral features in the late-time X-ray afterglow of the unusually long, slow-decaying GRB 130925A using NuSTAR, Swift-XRT, and Chandra. A spectral component in addition to an absorbed power-law is required at $>4\sigma$ significance, and its spectral shape varies between two observation epochs at $2\times10^5$ and $10^6$ seconds after the burst. Several models can fit this additional component, each with very different physical implications. A broad, resolved Gaussian absorption feature of several keV width improves the fit, but it is poorly constrained in the second epoch. An additive black body or second power-law component provide better fits. Both are challenging to interpret: the blackbody radius is near the scale of a compact remnant ($10^8$ cm), while the second powerlaw component requires an unobserved high-energy cutoff in order to be consistent with the non-detection by Fermi-LAT.
%U http://arxiv.org/abs/1402.6755v1