Early Afterglows of Gamma-Ray Bursts in a Stratified Medium with a Power-Law Density Distribution

Abstract

A long-duration gamma-ray burst (GRB) has been widely thought to arise from the collapse of a massive star, and it has been suggested that its ambient medium is a homogenous interstellar medium (ISM) or a stellar wind. There are two shocks when an ultra-relativistic fireball that has been ejected during the prompt gamma-ray emission phase sweeps up the circumburst medium: a reverse shock that propagates into the fireball, and a forward shock that propagates into the ambient medium. In this paper, we investigate the temporal evolution of the dynamics and emission of these two shocks in an environment with a general density distribution of $n\propto R^{-k}$ (where $R$ is the radius) by considering thick-shell and thin-shell cases. A GRB afterglow with one smooth onset peak at early times is understood to result from such external shocks. Thus, we can determine the medium density distribution by fitting the onset peak appearing in the light curve of an early optical afterglow. We apply our model to 19 GRBs, and find that their $k$ values are in the range of 0.4 - 1.4, with a typical value of $k\sim 1$, implying that this environment is neither a homogenous interstellar medium with $k=0$ nor a typical stellar wind with $k=2$. This shows that the progenitors of these GRBs might have undergone a new mass-loss evolution.

32 pages, 5 figures, 1 table, published in ApJ

References in corpus (16)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• An enigmatic long-lasting gamma-ray burst not accompanied by a bright supernova
• X-Ray Flares from Postmerger Millisecond Pulsars
• A Comprehensive Analysis of Swift/XRT Data: III. Jet Break Candidates in X-ray and Optical Afterglow Lightcurves
• The X-ray afterglow flat segment in short GRB 051221A: Energy injection from a millisecond magnetar?
• The First Swift Ultra-Violet/Optical Telescope GRB Afterglow Catalog
• A Comprehensive Study of Gamma-Ray Burst Optical Emission: II. Afterglow Onset and Late Re-Brightening Components
• Looking Into the Fireball: ROTSE-III and Swift Observations of Early GRB Afterglows
• Rise and fall of the X-ray flash 080330: an off-axis jet?
• The complex light-curve of the afterglow of GRB071010A
• Spin Evolution of Millisecond Magnetars with Hyperaccreting Fallback Disks: Implications for Early Afterglows of Gamma-Ray Bursts
• Multi-wavelength afterglow observations of the high redshift GRB 050730
• GRB 060605: multi-wavelength analysis of the first GRB observed using integral field spectroscopy
• Swift-UVOT captures the earliest ultraviolet spectrum of a Gamma Ray Burst
• Early emission of rising optical afterglows: The case of GRB 060904B and GRB 070420
• Evidence for energy injection and a fine-tuned central engine at optical wavelengths in GRB 070419A

Cited by in corpus (47)

• A Complete Reference of the Analytical Synchrotron External Shock Models of Gamma-Ray Bursts
• How Bad/Good Are the External Forward Shock Afterglow Models of Gamma-Ray Bursts?
• Comprehensive study of the X-ray flares from gamma-ray bursts observed by Swift
• A Comprehensive Radio View of the Extremely Bright Gamma-Ray Burst 130427A
• Phenomenology of Reverse-Shock Emission in the Optical Afterglows of Gamma Ray Bursts
• On the origin of the multi-GeV photons from the closest burst with intermediate luminosity: GRB 190829A
• Self-similar relativistic blast waves with energy injection
• The three-parameter correlations about optical plateaus of gamma-ray bursts
• Multi-wavelength afterglows of fast radio bursts
• Polarization Evolution of Early Optical Afterglows of Gamma-Ray Bursts
• Statistical study of gamma-ray bursts with jet break feature in multi-wavelength afterglow emissions
• Gamma-ray burst afterglow plateau break time - luminosity correlations favour thick shell models over thin shell models
• Statistical Distributions of Optical Flares from Gamma-Ray Bursts
• The Bright Reverse Shock Emission in the Optical Afterglows of Gamma-ray Bursts in a Stratified Medium
• Constraints on the Bulk Lorentz Factors of GRB X-Ray Flares
• Extremely bright GRB 160625B with multi-episodes emission: Evidences for long-term ejecta evolution
• Gamma-ray burst afterglow blast waves
• Statistical analyses on the energies of X-ray plateaus and flares in gamma-ray bursts
• Very Bright Prompt and Reverse Shock Emission of GRB 140512A
• A detailed radio study of the energetic, nearby and puzzling GRB 171010A
• The origin of the plateau and late rebrightening in the afterglow of GRB 120326A
• GRB 140102A: Insight into Prompt Spectral Evolution and Early Optical Afterglow Emission
• Early-time VLA observations and broad-band afterglow analysis of the Fermi-LAT detected GRB 130907A
• Simulation and physical model based gamma-ray burst afterglow analysis
• GRB120729A: external shock origin for both the prompt gamma-ray emission and afterglow
• Reverse Shock Emission in Gamma-ray Bursts Revisited
• Modeling Gamma-ray burst Afterglow observations with an Off-axis Jet emission
• Testing Blandford-Znajek mechanism in black hole hyperaccretion flows for long-duration gamma-ray bursts
• Afterglow light curves of the non-relativistic ejecta mass in a stratified circumstellar medium
• Evidence for a compact stellar merger origin for GRB 230307A from Fermi-LAT and multi-wavelength afterglow observations
• Constraining Properties of GRB Central Engines with X-ray flares
• Closure Relations of Synchrotron Self-Compton in Afterglow stratified medium and Fermi-LAT Detected Gamma-Ray Bursts
• GRB 191016A: The onset of the forward shock and evidence of late energy injection
• Photometric and Spectroscopic Observations of GRB 210104A: Bright Reverse shock Emission and Dense Circumburst Environment
• The expansion of the GRB 221009A afterglow
• External Shock in a Multi-Bursting Gamma-ray Burst: Energy Injection Phase induced by the Later Launched Ejecta
• Constraining the circumburst medium of gamma-ray bursts with X-ray afterglows
• Afterglow polarizations in a stratified medium with effect of the equal arrival time surface
• The Multiband Emission of the two-component Gamma-Ray Burst jet influenced by progenitor winds within the Accretion Disk of Active Galactic Nuclei
• Photometric and Spectroscopic Observations of GRB 140629A
• GRB Afterglow of the Sub-relativistic Materials with Energy Injection
• Diagnosing Circumburst Environment with Multiband Gamma-Ray Burst Radio Afterglows
• Constraining External Reverse Shock Physics of GRBs from ROTSE-III Limits
• A semi-analytical solution to the forward-reverse shock hydrodynamics of the gamma-ray burst afterglow
• The Double-Burst Nature and Early Afterglow Evolution of Long GRB 110801A
• Revisiting early afterglows of gamma-ray bursts with finite-thickness ejecta: Implications from XRF 080330 and GRB 080710
• Gamma-Ray Bursts, Supernovae Ia and Baryon Acoustic Oscillations: a binned cosmological analysis