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Author Basak, Rupal ♦ Rao, A. R.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ AFTERGLOW ♦ COMPARATIVE EVALUATIONS ♦ COOLING ♦ COSMIC GAMMA BURSTS ♦ COSMIC PHOTONS ♦ DATA ANALYSIS ♦ HARD X RADIATION ♦ JETS ♦ KEV RANGE ♦ LAYERS ♦ PHOTON EMISSION ♦ RESOLUTION ♦ SOFT X RADIATION ♦ TELESCOPES
Abstract GRB 130925A is an ultra-long gamma-ray burst (GRB), and it shows clear evidence for thermal emission in the soft X-ray data of the Swift/X-ray Telescope (XRT; ∼0.5 keV), lasting until the X-ray afterglow phase. Due to the long duration of the GRB, the burst could be studied in hard X-rays with high-resolution focusing detectors (NuSTAR). The blackbody temperature, as measured by the Swift/XRT, shows a decreasing trend until the late phase (Piro et al.) whereas the high-energy data reveal a significant blackbody component during the late epochs at an order of magnitude higher temperature (∼5 keV) compared to contemporaneous low energy data (Bellm et al.). We resolve this apparent contradiction by demonstrating that a model with two black bodies and a power law (2BBPL) is consistent with the data right from the late prompt emission to the afterglow phase. Both blackbodies show a similar cooling behavior up to late times. We invoke a structured jet, having a fast spine and a slower sheath layer, to identify the location of these blackbodies. Independent of the physical interpretation, we propose that the 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 GRBs reflects the lingering thermal component of the prompt emission with different timescales. We strengthen this proposal by pointing out a close similarity between the spectral evolutions of this GRB and GRB 090618, a source with significant wide band data during the early afterglow phase.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-07-01
Publisher Place United States
Journal Astrophysical Journal
Volume Number 807
Issue Number 1


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