Early GRB afterglows from reverse shocks in ultra-relativistic long-lasting winds

Abstract

We develop a model of early GRB afterglows with the dominant $X$-ray contribution from the reverse shock (RS) propagating in highly relativistic (Lorentz factor ${\gamma }_w\sim 10^6$) magnetized wind of a long-lasting central engine. The model reproduces, in a fairly natural way, the overall trends and yet allows for variations in the temporal and spectral evolution of early optical and $X$-ray afterglows. The high energy and the optical synchrotron emission from the RS particles occurs in the fast cooling regime; the resulting synchrotron power $L_s$ is a large fraction of the wind luminosity, $L_s\approx L_w/\sqrt{1+{\sigma }_w}$ ($L_w$ and ${\sigma }_w$ are wind power and magnetization). Thus, plateaus - parts of afterglow light curves that show slowly decreasing spectral power - are a natural consequence of the RS emission. Contribution from the forward shock (FS) is negligible in the $X$-rays, but in the optical both FS and RS contribute similarly: the FS optical emission is in the slow cooling regime, producing smooth components, while the RS optical emission is in the fast cooling regime, and thus can both produce optical plateaus and account for fast optical variability correlated with the $X$-rays, e.g., due to changes in the wind properties. We discuss how the RS emission in the $X$-rays and combined FS and RS emission in the optical can explain many of puzzling properties of early GRB afterglows.

References in corpus (49)

• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• The Physics of Gamma-Ray Bursts
• Gamma-Ray Bursts and the Fireball Model
• Optical and Long Wavelength Afterglow from Gamma-Ray Bursts
• Gamma-Ray Bursts
• The Physics of Gamma-Ray Bursts and Relativistic Jets
• Evidence for a Canonical GRB Afterglow Light Curve in the Swift/XRT Data
• The Shape of Spectral Breaks in GRB Afterglows
• The Proto-Magnetar Model for Gamma-Ray Bursts
• How to Tell a Jet from a Balloon: A Proposed Test for Beaming in Gamma Ray Bursts
• Short Gamma-Ray Bursts with Extended Emission
• Afterglow Emission from Naked Gamma-Ray Bursts
• Interpenetrating plasma shells: near-equipartition magnetic field generation and non-thermal particle acceleration
• Off-Axis Afterglow Emission from Jetted Gamma-Ray Bursts
• GRB990123, The Optical Flash and The Fireball Model
• The Afterglows of Swift-era Gamma-Ray Bursts. I. Comparing pre-Swift and Swift era Long/Soft (Type II) GRB Optical Afterglows
• The Third Swift Burst Alert Telescope Gamma-Ray Burst Catalog
• Hydrodynamic Time Scales and Temporal Structure of GRBs
• On the structure of relativistic collisionless shocks in electron-ion plasmas
• Jet breaks and Energetics of Swift GRB X-ray Afterglows
• Swift observations of GRB 070110: an extraordinary X-ray afterglow powered by the central engine
• GRB 990123: Reverse and Internal Shock Flashes and Late Afterglow
• Cooling Time Scales and Temporal Structure of Gamma-Ray Bursts
• Short GRB 130603B: Discovery of a jet break in the optical and radio afterglows, and a mysterious late-time X-ray excess
• Off-Axis Gamma-Ray Burst Afterglow Modeling Based On A Two-Dimensional Axisymmetric Hydrodynamics Simulation
• Some Observational Consequences of GRB Shock Models
• Gamma-ray bursts with continuous energy injection and their afterglow signature
• On the Mechanism of Gamma-Ray Burst Afterglows
• Can the early X-ray afterglow of GRBs be explained by a contribution from the reverse shock?
• The electromagnetic model of Gamma Ray Bursts
• A Reverse Shock in GRB 130427A
• "Late prompt" emission in Gamma Ray Bursts?
• Activation of the Blandford-Znajek mechanism in collapsing stars
• Different progenitors of short hard gamma-ray bursts
• X-ray flares and the duration of engine activity in gamma-ray bursts
• Model of extended emission of short Gamma-ray Bursts
• Gamma Ray Bursts in the Swift-Fermi Era
• Close Binary Progenitors of Long Gamma Ray Bursts
• Slowly balding black holes
• Jet-breaks in the X-ray Light-Curves of Swift GRB Afterglows
• Unveiling the population of orphan Gamma Ray Bursts
• Early afterglow detection in the Swift observations of GRB 050801
• The 80 Ms follow-up of the X-ray afterglow of GRB 130427A challenges the standard forward shock model
• The electromagnetic model of short GRBs, the nature of prompt tails, supernova-less long GRBs and highly efficient episodic accretion
• X-ray flares from propagation instabilities in long Gamma-Ray Burst jets
• The inner knot of the Crab nebula
• Implications of the Visible and X-Ray Counterparts to GRB970228
• On the Implications of Recent Observations of the Inner Knot in the Crab Nebula
• Double explosions and jet formation in GRB-supernova progenitors

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