62 citations · 198 across the 19 of their papers we have counts for
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JWST's Dusty Blue BOAT -- GRB 221009A
Nguyen M. Khang, Gavin P. Lamb, Helena-M. S. Grabham +6
GRB 221009A, the Brightest Of All Time (BOAT), presents a challenge for afterglow modelling due to its low Galactic latitude and consequent high line-of-sight extinction. This has…
Ultraviolet Signatures of Jet-Ejecta Interaction in Early Kilonovae: Prediction from Realistic Atomic Opacities
Smaranika Banerjee, Hamid Hamidani, Kyohei Kawaguchi +1
We investigate the signature of the jet-ejecta interaction in early kilonova (t < 1day) using detailed atomic opacities developed in Banerjee et al. (2020, 2024), appropriate for e…
Multiwavelength Modeling of the Luminous Fast Blue Optical Transient AT2024wpp
Conor M. B. Omand, Nikhil Sarin, Gavin P. Lamb +14
Luminous fast blue optical transients (LFBOTs) are a growing class of enigmatic energetic transients. They show fast rises and declines, high temperatures throughout their evolutio…
EP250108a/SN 2025kg: A Jet-Driven Stellar Explosion Interacting With Circumstellar Material
Gokul P. Srinivasaragavan, Hamid Hamidani, Genevieve Schroeder +28
We present optical, radio, and X-ray observations of EP250108a/SN 2025kg, a broad-line Type Ic supernova (SN Ic-BL) accompanying an Einstein Probe (EP) fast X-ray transient (FXT) a…
EP240414a: A Gamma-Ray Burst Jet Weakened by an Extended Circumstellar Material
Hamid Hamidani, Yuri Sato, Kazumi Kashiyama +3
The recent Einstein Probe (EP) event EP240414a exhibits several unusual observational features. Its prompt and afterglow emissions place it between long gamma-ray bursts (LGRBs) an…
Gamma-Ray Burst Jets in Circumstellar Material: Dynamics, Breakout, and Diversity of Transients
Hamid Hamidani, Kunihito Ioka, Kazumi Kashiyama +1
Recent observations indicate that stripped-envelope core-collapse supernovae are often surrounded by dense circumstellar material (CSM). Motivated by this, we develop an analytic m…
Prompt Periodicity in the GRB 211211A Precursor: Black-hole or magnetar engine?
Gavin P. Lamb, Thomas Baxter, Conor M. B. Omand +18
The merger origin long GRB 211211A was a class (re-)defining event. A precursor was identified with a s separation from the main burst, as well as a claimed candidate quas…
GRB 211211A: The Case for an Engine Powered over r-Process Powered Blue Kilonova
Hamid Hamidani, Masaomi Tanaka, Shigeo S. Kimura +2
The recent Gamma-Ray Burst (GRB) GRB 211211A provides the earliest ( h) data of a kilonova (KN) event, displaying bright ( erg s) and blue early emissio…
High-energy neutrinos from late-time jets of gamma-ray bursts seeded with cocoon photons
Riki Matsui, Shigeo S Kimura, Hamid Hamidani
In gamma-ray bursts (GRBs), 100 - 1000 s after the prompt emission, afterglow observations have consistently shown X-ray excesses detected in the form of flares (XFs; in lon…
Possible X-ray Cocoon Emission from GRB 050709
Naoki Ogino, Makoto Arimoto, Hamid Hamidani +6
The detection of the short gamma-ray burst (SGRB) 050709 by the HETE-2 satellite opened a new window into understanding the nature of SGRBs, offering clues about their emission mec…
Three dimensional end-to-end simulation for kilonova emission from a black-hole neutron-star merger
Kyohei Kawaguchi, Nanae Domoto, Sho Fujibayashi +5
We study long-term evolution of the matter ejected in a black-hole neutron-star (BH-NS) merger employing the results of a long-term numerical-relativity simulation and nucleosynthe…
Peak energy--Isotropic Luminosity Correlation and Jet Opening Angle Evolution in Swift-BAT Short GRBs with Soft Tail Emission
Naoki Ogino, Daisuke Yonetoku, Makoto Arimoto +2
Some short gamma-ray bursts (SGRBs) exhibit a short duration and spectral hard emission (referred to as a "hard spike") followed by a slightly longer soft emission (known as a "sof…
Late Engine Activity in Neutron Star Mergers and Its Cocoon: An Alternative Scenario for the Blue Kilonova
Hamid Hamidani, Shigeo S. Kimura, Masaomi Tanaka +1
Follow-up observations of short gamma-ray bursts (sGRBs) have continuously unveiled late extended/plateau emissions, attributed to jet launch due to late engine activity, the natur…
A search for extragalactic fast optical transients in the Tomo-e Gozen high-cadence survey
Kakeru Oshikiri, Masaomi Tanaka, Nozomu Tominaga +15
The population of optical transients evolving within a time-scale of a few hours or a day (so-called fast optical transients, FOTs) has recently been debated extensively. In partic…
Cocoon breakout and escape from the ejecta of neutron star mergers
Hamid Hamidani, Kunihito Ioka
The cocoon is an inevitable product of a jet propagating through ambient matter, and takes a fair fraction of the jet energy. In short gamma-ray bursts, the ambient matter is the e…
Cocoon cooling emission in neutron star mergers
Hamid Hamidani, Kunihito Ioka
In the gravitational wave event GW170817, there was a hours gap before electromagnetic (EM) observations, without detection of the cocoon. The cocoon is heated by a \text…
Jet Propagation in Expanding Medium for Gamma-Ray Bursts
Hamid Hamidani, Kunihito Ioka
The binary neutron star (BNS) merger event GW170817 clearly shows that a BNS merger launches a short Gamma-Ray Burst (sGRB) jet. Unlike collapsars, where the ambient medium is stat…
Jet Propagation in Neutron Star Mergers and GW170817
Hamid Hamidani, Kenta Kiuchi, Kunihito Ioka
The gravitational wave event from the binary neutron star (BNS) merger GW170817 and the following multi-messenger observations present strong evidence for i) merger ejecta expandin…
Ideal Engine Durations For Gamma-Ray-Burst-Jet Launch
Hamid Hamidani, Koh Takahashi, Hideyuki Umeda +1
Aiming to study GRB engine duration, we present numerical simulations to investigate collapsar jets. We consider typical explosion energy ( erg) but different engine durat…