Giant X-ray and optical Bump in GRBs: evidence for fall-back accretion model

Abstract

The successful operation of dedicated detectors has brought us valuable information for understanding the central engine and the progenitor of gamma-ray bursts (GRBs). For instance, the giant X-ray and optical bumps found in some long-duration GRBs (e.g. GRBs 121027A and 111209A) imply that some extended central engine activities, such as the late X-ray flares, are likely due to the fall-back of progenitor envelope materials. Here we systemically search for long GRBs that consist of a giant X-ray or optical bump from the Swift GRB sample, and eventually we find 19 new possible candidates. The fall-back accretion model could well interpret the X-ray and optical bump for all candidates within a reasonable parameter space. Six candidates showing simultaneous bump signatures in both X-ray and optical observations, which could be well fitted at the same time when scaling down the X-ray flux into optical by one order of magnitude, are consistent with the standard $F_{\nu }\propto {\nu }^{1/3}$ synchrotron spectrum. The typical fall-back radius is distributed around $10^{10}-10^{12}$ cm, which is consistent with the typical radius of a Wolf-Rayet star. The peak fall-back accretion rate is in the range of $\sim 10^{-11}-10^{-4}{M}_{\odot }{\text{s}}^{-1}$ at time $\sim 10^2-10^5\mathrm{s}$, which is relatively easy to fulfill as long as the progenitor's metallicity is not too high. Combined with the sample we found, future studies of the mass supply rate for the progenitors with different mass, metallicity, and angular momentum distribution would help us to better constrain the progenitor properties of long GRBs.

accepted for publication by ApJ

References in corpus (22)

• The Supernova -- Gamma-Ray Burst Connection
• Neutrino-Cooled Accretion Disks around Spinning Black Hole
• A Comprehensive Analysis of the Swift/XRT Data: II. Diverse Physical Origins of the Shallow Decay Segment
• The Millisecond Magnetar Central Engine in short GRBs
• Fallback and Black Hole Production in Massive Stars
• Mass Fall-back and Accretion in the Central Engine of Gamma-Ray Bursts
• Hyper-accreting black hole as GRB central engine. I: Baryon loading in GRB jets
• 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 Ep,i - Eiso correlation: type I gamma-ray bursts and the new classification method
• Neutrino-Dominated Accretion Models for Gamma-Ray Bursts: Effects of General Relativity and Neutrino Opacity
• Properties of Gamma-Ray Burst Progenitor Stars
• Giant X-ray Bump in GRB 121027A: Evidence for Fall-back Disk Accretion
• Magnetically Torqued Neutrino-Dominated Accretion Flows for Gamma-ray Bursts
• Hyperaccreting Black Hole as Gamma-Ray Burst Central Engine. II. Temporal evolution of central engine parameters during Prompt and Afterglow Phases
• The optically unbiased GRB host (TOUGH) survey. V. VLT/X-shooter emission-line redshifts for Swift GRBs at z~2
• Jet Luminosity of Gamma-ray Bursts: Blandford-Znajek Mechanism v.s. Neutrino Annihilation Process
• Black hole hyperaccretion inflow-outflow model. I. long and ultra-long gamma-ray bursts
• Signature of a New-Born Black Hole from the Collapse of a Supra-massive Millisecond Magnetar
• Numerical and analytical solutions of Neutrino-Dominated Accretion Flows with a Non-Zero Torque Boundary Condition and its applications in Gamma-ray Bursts
• Relation between the intrinsic and observed central engine activity time: implications for ultra-long GRBs
• The Second Plateau in X-ray Afterglow Providing Additional Evidence for Rapidly Spinning Magnetars as the GRB Central Engine

Cited by in corpus (1)

• Science objectives of the Einstein Probe mission