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GRB 130925A is an ultra-long GRB, and it shows clear evidences for a thermalemission in the soft X-ray data of \emph{Swift}/XRT ($\sim0.5$\,keV), lastingtill the X-ray afterglow phase. Due to the long duration of the GRB, the burstcould be studied in hard X-rays with high-resolution focusing detectors(\emph{NuSTAR}). The blackbody temperature, as measured by the\emph{Swift}/XRT, shows a decreasing trend till the late phase (Piro et al.2014) whereas the high-energy data reveals a significant blackbody componentduring the late epochs at an order of magnitude higher temperature($\sim5$\,keV), as compared to the contemporaneous low energy data (Bellm etal. 2014). We resolve this apparent contradiction by demonstrating that a modelwith two black bodies and a power-law (2BBPL) is consistent with the data rightfrom the late prompt emission to the afterglow phase. Both the blackbodies showa similar cooling behaviour upto the late time. We invoke a structured jet,having a fast spine and a slower sheath layer, to identify the location ofthese blackbodies. Independent of the physical interpretation, we propose thatthe 2BBPL model is a generic feature of the prompt emission of all long GRBs,and the thermal emission found in the afterglow phase of different GRBsreflects the lingering thermal component of the prompt emission with diversetime-scales. We strengthen this proposal by pointing out a close similaritybetween the spectral evolutions of this GRB and GRB~090618, a source withsignificant wide band data during the early afterglow phase.

Thermal Emissions Spanning the Prompt and the Afterglow Phase of the Ultra-long GRB 130925A