GCN Circular 15286
E. C. Bellm, F. A. Harrison, K. Forster, K. K. Madsen, V. Rana (Caltech), S. E. Boggs, J. Tomsick (U.C. Berkeley), J. M. Miller (Michigan), and S. B. Cenko (NASA/GSFC) report on behalf of the NuSTAR collaboration: NuSTAR observed the unusual ultra-long GRB/TDE candidate GRB 130925A (GCN 15246) beginning 44.3 hours after the Swift trigger for a total of 39.2 ksec exposure time. NuSTAR detects the source to >20 keV; the average 3-20 keV flux over the interval was 1.3E-12 erg/cm^-2/s^-1. The data may be fit with an absorbed power law with spectral index Gamma ~ 3. NuSTAR observes a broad absorption feature centered near 6 keV. Simultaneous Swift-XRT spectra support the existence of this feature at lower SNR. An F-test of a Gaussian absorption feature fit to the combined data sets yields a detection significance of 5.5 sigma. Preliminary searches for features in the early-time XRT data have not identified any clear signatures; additional tests are ongoing. Further observations are in progress; we encourage continued monitoring of this interesting event at all wavelengths. We thank the NuSTAR Mission Operations Team for the rapid turnaround that enabled this observation.