A VLA Study of High-redshift GRBs II - The Complex Radio Afterglow of GRB 140304A: Shell Collisions and Two Reverse Shocks

Abstract

We present detailed multi-frequency, multi-epoch radio observations of GRB 140304A at $z=5.283$ from 1 to 86 GHz and 0.45 d to 89 d. The radio and mm data exhibit unusual multiple spectral components, which cannot be simply explained by standard forward and reverse shock scenarios. Through detailed multi-wavelength analysis spanning radio to X-rays, we constrain the forward shock parameters to $E_{\mathrm{K},\mathrm{iso}}\approx 4.9\times 10^{54}$erg, $A_{\ast }\approx 2.6\times 10^{-2}$, ${\epsilon }_{\mathrm{e}}\approx 2.5\times 10^{-2}$, ${\epsilon }_{\mathrm{B}}\approx 5.9\times 10^{-2}$, $p\approx 2.6$, and ${\theta }_{\mathrm{jet}}\approx 1.1^{\circ }$, yielding a beaming corrected $\gamma$-ray and kinetic energy, $E_{\gamma }\approx 2.3\times 10^{49}$erg and $E_{\mathrm{K}}\approx 9.5\times 10^{50}$erg, respectively. We model the excess radio emission as due to a combination of a late-time reverse shock (RS) launched by a shell collision, which also produces a re-brightening in the X-rays at $\approx 0.26$d, and either a standard RS or diffractive interstellar scintillation. Under the standard RS interpretation, we invoke consistency arguments between the forward and reverse shocks to derive a deceleration time, $t_{\mathrm{dec}}\approx 100$s, the ejecta Lorentz factor, $\Gamma (t_{\mathrm{dec}})\approx 300$, and a low RS magnetization, $R_{\mathrm{B}}\approx 0.6$. Our observations highlight both the power of radio observations in capturing RS emission and thus constraining the properties of GRB ejecta and central engines, and the challenge presented by interstellar scintillation in conclusively identifying RS emission in GRB radio afterglows.

24 pages, 17 figures, 7 tables; submitted to ApJ

References in corpus (14)

• The Supernova -- Gamma-Ray Burst Connection
• An online repository of Swift/XRT light curves of GRBs
• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
• Mass Fall-back and Accretion in the Central Engine of Gamma-Ray Bursts
• Fallback accretion in the aftermath of a compact binary merger
• Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow
• A unifying view of Gamma Ray Burst Afterglows
• Flares in GRB afterglows from delayed magnetic dissipation
• What can we learn from "internal plateaus"? The peculiar afterglow of GRB 070110
• A common stochastic process rules gamma-ray burst prompt emission and X-ray flares
• Flares in Gamma Ray Bursts: Disc Fragmentation and Evolution
• A VLA Study of High-redshift GRBs I - Multi-wavelength Observations and Modeling of GRB 140311A
• Relativistic simulations of long-lived reverse shocks in stratified ejecta: the origin of flares in GRB afterglows
• Ultra-relativistic double explosions

Cited by in corpus (26)

• Particle acceleration in astrophysical jets
• The Broad-band Counterpart of the Short GRB 200522A at $z=0.5536$: A Luminous Kilonova or a Collimated Outflow with a Reverse Shock?
• On the Cosmological Evolution of Long Gamma-ray Burst Properties
• ALMA Detection of a Linearly Polarized Reverse Shock in GRB 190114C
• Luminous Millimeter, Radio, and X-ray Emission from ZTF20acigmel (AT2020xnd)
• A Reverse Shock in GRB 181201A
• First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B
• ZTF20aajnksq (AT2020blt): A Fast Optical Transient at $z\approx 2.9$ With No Detected Gamma-Ray Burst Counterpart
• GRB 160625B: Evidence for a Gaussian-Shaped Jet
• The Evolution of Gamma-ray Burst Jet Opening Angle through Cosmic Time
• Accounting for Selection Bias and Redshift Evolution in GRB Radio Afterglow Data
• A detailed radio study of the energetic, nearby and puzzling GRB 171010A
• Extragalactic Millimeter Transients in the Era of Next Generation CMB Surveys
• The Consequences of Gamma-ray Burst Jet Opening Angle Evolution on the Inferred Star Formation Rate
• Interpretation of Radio Afterglows in the framework of the Standard Fireball and Energy Injection models
• Resolving the Excess of Long GRBs at low redshift in the Swift Era
• Radio data challenge the broadband modelling of GRB160131A afterglow
• On the Anti-Correlation between Duration and Redshift in Gamma-ray Bursts
• An energy-conserving dynamical model of GRB afterglows from magnetized forward and reverse shocks
• Diagnosing Circumburst Environment with Multiband Gamma-Ray Burst Radio Afterglows
• Discovery and Analysis of Afterglows from Poorly Localised GRBs with the Gravitational-wave Optical Transient Observer (GOTO) All-sky Survey
• Multi-epoch afterglow rebrightenings in GRB 250129A: Evidence for successive shock interactions
• The GROND GRB sample: II. Fireball parameters for four GRB afterglows
• Connecting the early afterglow to the prompt GRB and the central engine in the striped jet model
• A Radio-selected Population of Dark, Long Gamma-ray Bursts: Comparison to the Long Gamma-ray Burst Population and Implications for Host Dust Distributions
• GRB 260310A / SN 2026fgk: A Multi-Wavelength Study of a Nearby Underluminous Long GRB and SN with a Complex Afterglow