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1. 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)
2. The Short GRB 170817A: Modeling the Off-axis Emission and Implications on the Ejecta Magnetization

   https://doi.org/10.3847/1538-4357/aaf564  

   Fraija, N.; Colle, F. De; Veres, P.; Dichiara, S.; Duran, R. Barniol; Galvan-Gamez, A.; do E. S. Pedreira, A. C. (January 2019, The Astrophysical Journal)
3. The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A

   https://doi.org/10.3847/2041-8213/ac8421  

   Laskar, Tanmoy; Escorial, Alicia Rouco; Schroeder, Genevieve; Fong, Wen-fai; Berger, Edo; Veres, Péter; Bhandari, Shivani; Rastinejad, Jillian; Kilpatrick, Charles D.; Tohuvavohu, Aaron; et al (August 2022, The Astrophysical Journal Letters)

   Abstract We present the discovery of the first millimeter afterglow of a short-durationγ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲z≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction,A_V≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at $t_{\mathrm{jet}}={29.2}_{-4.0}^{+4.5}$days. For a presumed redshift ofz= 1, we infer an opening angle,θ_jet= (15.°5 ± 1.°4), and beaming-corrected kinetic energy of $\log \left(E_{\mathrm{K}}/\mathrm{erg}\right)=51.8\pm 0.3$, making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%–40% on timescales of ≳2 days at rates of ≈0.8–1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows. 

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4. 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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5. GRB 191019A: A Short Gamma-Ray Burst in Disguise from the Disk of an Active Galactic Nucleus

   https://doi.org/10.3847/2041-8213/acd18c  

   Lazzati, Davide; Perna, Rosalba; Gompertz, Benjamin P.; Levan, Andrew J. (June 2023, The Astrophysical Journal Letters)

   Abstract Long and short gamma-ray bursts (GRBs), canonically separated at around 2 s duration, are associated with different progenitors: the collapse of a massive star and the merger of two compact objects, respectively. GRB 191019A was a long GRB (T₉₀∼ 64 s). Despite the relatively small redshiftz= 0.248 and Hubble Space Telescope follow-up observations, an accompanying supernova was not detected. In addition, the host galaxy did not have significant star formation activity. Here we propose that GRB 191019A was produced by a binary compact merger, whose prompt emission was stretched in time by the interaction with a dense external medium. This would be expected if the burst progenitor was located in the disk of an active galactic nucleus, as supported by the burst localization close to the center of its host galaxy. We show that the light curve of GRB 191019A can be well modeled by a burst of intrinsic durationt_eng= 1.1 s and of energyE_iso= 10⁵¹erg seen moderately off axis, exploding in a medium of density ∼10⁷–10⁸cm⁻³. The double-peaked light curve carries the telltale features predicted for GRBs in high-density media, where the first peak is produced by the photosphere and the second by the overlap of reverse shocks that take place before the internal shocks could happen. This would make GRB 191019A the first confirmed stellar explosion from within an accretion disk, with important implications for the formation and evolution of stars in accretion flows and for gravitational-waves source populations. 

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