Broadband Modelling of GRB 230812B Afterglow: Implications for VHE $\gamma$-ray Detection with IACTs

Abstract

A significant fraction of the energy from the $\gamma$-ray burst (GRB) jets, after powering the keV-MeV emission, forms an ultra-relativistic shock propagating into the circumburst medium. The particles in the medium accelerate through the shock and produce afterglow emission. Recently, a few GRB afterglows have been observed in TeV $\gamma$-rays by Cherenkov Telescopes. This provides access to broadband spectra of GRB afterglows containing rich information about the microphysics of relativistic shocks and the profile of the circumburst medium. Since the transition from synchrotron to inverse Compton regime in afterglow spectra occurs between hard X-rays and the very-high-energy (VHE) $\gamma$-rays, detection in one of these bands is required to identify the two spectral components. The early afterglow data in the hard X-rays, along with the GeV emission, could accurately constrain the spectral shape and help in capturing the spectral turnover to distinguish the two components. We present the multiwavelength spectral and temporal study, focused on the keV-VHE domain, of GRB 230812B, one of the brightest GRBs detected by Fermi Gamma Ray Burst Monitor (GBM), along with the detection of a 72 GeV photon in Large Area Telescope (LAT) during the early afterglow phase. Through a detailed modelling of the emission within the afterglow external forward shock in a wind-like scenario, we predict optical to high-energy observations up to ~1 day. We emphasize the importance of following up poorly localised GRBs by demonstrating that even without prompt sub-degree localisation, such as in GRB 230812B, it is possible to recover the emission using imaging atmospheric Cherenkov telescopes, thanks to their relatively wider field of view. Moreover, we show that the low energy threshold of Large-Sized Telescope is essential in discovering the VHE component at much higher redshifts, typical of long GRBs.

arXiv commentSubmitted. Comments and Suggestions are welcome

References in corpus (49)

• emcee: The MCMC Hammer
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• The Fermi Gamma-Ray Burst Monitor
• Unsteady Outflow Models for Cosmological Gamma-Ray Bursts
• Optical and Long Wavelength Afterglow from Gamma-Ray Bursts
• Physical processes shaping GRB X-ray afterglow lightcurves: theoretical implications from the Swift XRT observations
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Calibration of X-ray absorption in our Galaxy
• Extragalactic Background Light Inferred from AEGIS Galaxy SED-type Fractions
• The Shape of Spectral Breaks in GRB Afterglows
• Wind Interaction Models for Gamma-Ray Burst Afterglows: The Case for Two Types of Progenitors
• On The Synchrotron Self-Compton Emission from Relativistic Shocks and Its Implications for Gamma-Ray Burst Afterglows
• Analytic Light-Curves of Gamma-Ray Burst Afterglows: Homogeneous versus Wind External Media
• Efficient acceleration and radiation in Poynting flux powered GRB outflows
• Accretion Models of Gamma-Ray Bursts
• An Accurate Flux Density Scale from 50 MHz to 50 GHz
• The Fourth Fermi-GBM Gamma-Ray Burst Catalog: A Decade of Data
• Fundamental Physical Parameters of Collimated Gamma-Ray Burst Afterglows
• Radio Transients from Gamma-Ray Bursters
• Teraelectronvolt emission from the $\gamma$-ray burst GRB 190114C
• A very-high-energy component deep in the Gamma-ray Burst afterglow
• Images and Spectra From the Interior of a Relativistic Fireball
• A decade of Gamma-Ray Bursts observed by $Fermi$-LAT: The 2${}^{nd}$ GRB catalog
• The 3rd Fermi GBM Gamma-Ray Burst Catalog: The First Six Years
• External forward shock origin of high energy emission for three GRBs detected by Fermi
• Klein-Nishina Effects on Optically Thin Synchrotron and Synchrotron Self-Compton Spectrum
• GeV emission from Gamma Ray Bursts: a radiative fireball?
• A tera-electronvolt afterglow from a narrow jet in an extremely bright gamma-ray burst 221009A
• Cooling Time Scales and Temporal Structure of Gamma-Ray Bursts
• Prompt GRB emission from gradual energy dissipation
• Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow
• Spectral properties of 438 GRBs detected by Fermi/GBM
• The Fermi GBM Gamma-Ray Burst Catalog: The First Two Years
• Afterglow emission in Gamma-Ray Bursts: I. Pair-enriched ambient medium and radiative blast waves
• Spectra of Poynting-flux powered GRB outflows
• Spectra of Unsteady Wind Models of Gamma-Ray Bursts
• CAPTURE: A continuum imaging pipeline for the uGMRT
• Gamma-ray bursts afterglow physics and the VHE domain
• Multi-wavelength view of the close-by GRB 190829A sheds light on gamma-ray burst physics
• A morphological analysis of gamma-ray burst early optical afterglows
• GRB afterglow parameters in the era of TeV observations: the case of GRB~190114C
• Particle acceleration, magnetization and radiation in relativistic shocks
• MAGIC detection of GRB 201216C at $z=1.1$
• Constraining the intrinsic population of Long Gamma-Ray Bursts: implications for spectral correlations, cosmic evolution and their use as tracers of star formation
• Camelidae on BOAT: observation of a second spectral component in GRB 221009A
• Cross-Observatory Coordination with tilepy: A Novel Tool for Observations of Multi-Messenger Transient Events