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- Srinivasaragavan, Gokul P., et al.
(författare)
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Characterizing the Ordinary Broad-line Type Ic SN 2023pel from the Energetic GRB 230812B
- 2024
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 960:2
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Tidskriftsartikel (refereegranskat)abstract
- We report observations of the optical counterpart of the long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity (z = 0.36) and high energy (Eγ,iso ∼ 1053 erg) make it an important event to study as a probe of the connection between massive star core collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peak r-band magnitude of Mr = −19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN of MNi = 0.38 ± 0.01 M⊙ and a peak bolometric luminosity of Lbol ∼ 1.3 × 1043 erg s−1. We confirm SN 2023pel's classification as a broad-line Type Ic SN with a spectrum taken 15.5 days after its peak in the r band and derive a photospheric expansion velocity of vph = 11,300 ± 1600 km s−1 at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta mass Mej = 1.0 ± 0.6 M⊙ and kinetic energy EKE = 1.3 +3.3/-1.2 x 1051 erg. We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness and Eγ,iso for their associated GRBs across a broad range of 7 orders of magnitude provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems.
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- Lesage, S., et al.
(författare)
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Fermi-GBM Discovery of GRB 221009A : An Extraordinarily Bright GRB from Onset to Afterglow
- 2023
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Ingår i: Astrophysical Journal Letters. - : IOP Publishing Ltd. - 2041-8205 .- 2041-8213. ; 952:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the discovery of GRB 221009A, the highest flux gamma-ray burst (GRB) ever observed by the Fermi Gamma-ray Burst Monitor (Fermi-GBM). This GRB has continuous prompt emission lasting more than 600 s, which smoothly transitions to afterglow emission visible in the Fermi-GBM energy range (8 keV-40 MeV), and total energetics higher than any other burst in the Fermi-GBM sample. By using a variety of new and existing analysis techniques we probe the spectral and temporal evolution of GRB 221009A. We find no emission prior to the Fermi-GBM trigger time (t (0); 2022 October 9 at 13:16:59.99 UTC), indicating that this is the time of prompt emission onset. The triggering pulse exhibits distinct spectral and temporal properties suggestive of the thermal, photospheric emission of shock breakout, with significant emission up to & SIM;15 MeV. We characterize the onset of external shock at t (0) + 600 s and find evidence of a plateau region in the early-afterglow phase, which transitions to a slope consistent with Swift-XRT afterglow measurements. We place the total energetics of GRB 221009A in context with the rest of the Fermi-GBM sample and find that this GRB has the highest total isotropic-equivalent energy (E ( & gamma;,iso) = 1.0 x 10(55) erg) and second highest isotropic-equivalent luminosity (L ( & gamma;,iso) = 9.9 x 10(53) erg s(-1)) based on its redshift of z = 0.151. These extreme energetics are what allowed us to observe the continuously emitting central engine of Fermi-GBM from the beginning of the prompt emission phase through the onset of early afterglow.
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