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arXiv · 1402.6755

X-ray Spectral Components in the Afterglow of GRB 130925A

Eric C. Bellm·Nicolas M. Barriere·Varun Bhalerao·Steven E. Boggs·S. Bradley Cenko·Finn E. Christensen·William W. Craig·Karl Forster·Chris L. Fryer·Charles J. Hailey·Fiona A. Harrison·Assaf Horesh·Chryssa Kouveliotou·Kristin K. Madsen·Jon M. Miller·Eran O. Ofek·Daniel A. Perley·Vikram R. Rana·Stephen P. Reynolds·Daniel Stern·John A. Tomsick·William W. Zhang
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Abstract

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.

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Eric C. Bellm, Nicolas M. Barriere, Varun Bhalerao, Steven E. Boggs, S. Bradley Cenko, Finn E. Christensen, William W. Craig, Karl Forster, Chris L. Fryer, Charles J. Hailey, Fiona A. Harrison, Assaf Horesh, Chryssa Kouveliotou, Kristin K. Madsen, Jon M. Miller, Eran O. Ofek, Daniel A. Perley, Vikram R. Rana, Stephen P. Reynolds, Daniel Stern, John A. Tomsick, William W. Zhang. 2014-02-27. X-ray Spectral Components in the Afterglow of GRB 130925A. https://doi.org/10.1088/2041-8205/784/2/l19

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