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1. Characterizing the Ordinary Broad-line Type Ic SN 2023pel from the Energetic GRB 230812B

   https://doi.org/10.3847/2041-8213/ad16e7  

   Srinivasaragavan, Gokul P. ; Swain, Vishwajeet ; O’Connor, Brendan ; Anand, Shreya ; Ahumada, Tomás ; Perley, Daniel ; Stein, Robert ; Sollerman, Jesper ; Fremling, Christoffer ; Cenko, S. Bradley ; et al ( January 2024 , The Astrophysical Journal Letters)

   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 (E_γ,iso∼ 10⁵³erg) 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 peakr-band magnitude ofM_r= −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 ofM_Ni= 0.38 ± 0.01M_⊙and a peak bolometric luminosity ofL_bol∼ 1.3 × 10⁴³erg 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 therband and derive a photospheric expansion velocity ofv_ph= 11,300 ± 1600 km s⁻¹at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta massM_ej= 1.0 ± 0.6M_⊙and kinetic energy$E_{\mathrm{KE}}={1.3}_{-1.2}^{+3.3}\times {10}^{51}\mathrm{erg}$. 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 andE_γ,isofor 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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2. Self-similarities and Power Laws in the Time-resolved Spectra of GRB 190114C, GRB 130427A, GRB 160509A, and GRB 160625B

   https://doi.org/10.3847/1538-4357/acb20b  

   Li, Liang ; Rueda, J. A. ; Moradi, R. ; Wang, Y. ; Xue, S. S. ; Ruffini, R. ( March 2023 , The Astrophysical Journal)

   Abstract Binary-driven hypernova (BdHN) models have been adopted to explain the observed properties of long gamma-ray bursts (GRBs). Here, we perform a comprehensive data analysis (temporal and spectral analysis, GeV emission, and afterglow) on GRB 130427A, GRB 160509A, and GRB 160625B. We identify three specific episodes characterized by different observational signatures and show that these episodes can be explained and predicted to occur within the framework of the BdHNe I model, as first observed in GRB 190114C and reported in an accompanying paper. Episode 1 includes the “SN-rise” with the characteristic cutoff power-law spectrum; Episode 2 is initiated by the moment of formation of the black hole, coincident with the onset of the GeV emission and the ultrarelativistic prompt emission phase, and is characterized by a cutoff power law and blackbody spectra; Episode 3 is the “cavity,” with its characteristic featureless spectrum. 

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3. The First JWST Spectrum of a GRB Afterglow: No Bright Supernova in Observations of the Brightest GRB of all Time, GRB 221009A

   https://doi.org/10.3847/2041-8213/acc2c1  

   Levan, A. J. ; Lamb, G. P. ; Schneider, B. ; Hjorth, J. ; Zafar, T. ; de Ugarte Postigo, A. ; Sargent, B. ; Mullally, S. E. ; Izzo, L. ; D’Avanzo, P. ; et al ( March 2023 , The Astrophysical Journal Letters)

   Abstract We present James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) observations of the afterglow of GRB 221009A, the brightest gamma-ray burst (GRB) ever observed. This includes the first mid-IR spectra of any GRB, obtained with JWST/Near Infrared Spectrograph (0.6–5.5 micron) and Mid-Infrared Instrument (5–12 micron), 12 days after the burst. Assuming that the intrinsic spectral slope is a single power law, with F ν ∝ ν − β , we obtain β ≈ 0.35, modified by substantial dust extinction with A V = 4.9. This suggests extinction above the notional Galactic value, possibly due to patchy extinction within the Milky Way or dust in the GRB host galaxy. It further implies that the X-ray and optical/IR regimes are not on the same segment of the synchrotron spectrum of the afterglow. If the cooling break lies between the X-ray and optical/IR, then the temporal decay rates would only match a post-jet-break model, with electron index p < 2, and with the jet expanding into a uniform ISM medium. The shape of the JWST spectrum is near-identical in the optical/near-IR to X-SHOOTER spectroscopy obtained at 0.5 days and to later time observations with HST. The lack of spectral evolution suggests that any accompanying supernova (SN) is either substantially fainter or bluer than SN 1998bw, the proto-type GRB-SN. Our HST observations also reveal a disk-like host galaxy, viewed close to edge-on, that further complicates the isolation of any SN component. The host galaxy appears rather typical among long-GRB hosts and suggests that the extreme properties of GRB 221009A are not directly tied to its galaxy-scale environment. 

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4. GRB 210217A: a short or a long GRB?

   https://doi.org/10.1007/s12036-022-09822-x  

   Dimple ; Misra, Kuntal ; Ghosh, Ankur ; Arun, K. G. ; Gupta, Rahul ; Kumar, Amit ; Resmi, L. ; Pandey, S. B. ; Yadav, Lallan ( December 2022 , Journal of Astrophysics and Astronomy)
5. The Distant, Galaxy Cluster Environment of the Short GRB 161104A at z ∼ 0.8 and a Comparison to the Short GRB Host Population

   https://doi.org/10.3847/1538-4357/abc24a  

   Nugent, A. E. ; Fong, W. ; Dong, Y. ; Palmese, A. ; Leja, J. ; Escorial, A. Rouco ; Blanchard, P. K. ; Paterson, K. ; Chornock, R. ; Monson, A. ; et al ( November 2020 , The Astrophysical Journal)