Multi-color blackbody emission in GRB 081221

Abstract

The radiation mechanism of the prompt emission of gamma-ray bursts (GRBs) remains an open question. Although their spectra are usually well fitted with the empirical Band function, which is widely believed to be fully non-thermal and interpreted as an optically thin synchrotron emission, accumulating evidence shows that a thermal component actually exists. In this paper, a multi-color blackbody (mBB) model is proposed for the time-integrated spectrum of GRB 081221 by assuming a power-law distribution of the thermal luminosities with temperature, which manifests photospheric emissions from a different radius and/or angle. The effects of the minimum temperature $k{T}_{\min }$, the maximum temperature $k{T}_{\max }$ and the power law index $m$ of the luminosity distribution of an mBB are discussed. The fitting to the time-integrated spectrum during the bright phase (from 20s to 30s since the trigger) of GRB 081221 by the mBB model yields $k{T}_{\min }$ = $4.4\pm 0.3$ keV, $k{T}_{\max }$ = 57.0 ${}_{-1.4}^{+1.6}$ keV, and $m=-0.46_{-0.06}^{+0.05}$. When the time bin is small enough, the time-resolved spectra of GRB 081221 are well fitted with a series of single-temperature blackbodies. Our results imply the prompt emission of GRB 081221 is dominated by the photosphere emission and its time-integrated spectrum is a superposition of pure blackbody components at different times, indicating that some empirical Band spectra may be interpreted as mBB if the temperature is widely distributed.

arXiv commentAccepted for publication in the ApJ, 23 pages, 6 figures

References in corpus (43)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Fermi Gamma-Ray Burst Monitor
• Dissipative Photosphere Models of Gamma-ray Bursts and X-ray Flashes
• Steep Slopes and Preferred Breaks in GRB Spectra: the Role of Photospheres and Comptonization
• Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission
• The Complete Spectral Catalog of Bright BATSE Gamma-Ray Bursts
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data
• The Synchrotron Shock Model Confronts a `Line of Death' in the BATSE Gamma-Ray Burst Data
• Identification and properties of the photospheric emission in GRB090902B
• Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724B
• A Comprehensive Analysis of Fermi Gamma-Ray Burst Data. I. Spectral Components and Their Possible Physical Origins of LAT/GBM GRBs
• A complete sample of bright Swift Long Gamma-Ray Bursts: Sample presentation, Luminosity Function and evolution
• Is Thermal Emission in Gamma-Ray Bursts Ubiquitous?
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: The First Two Years
• GRB110721A: An extreme peak energy and signatures of the photosphere
• Temporal Evolution Of Thermal Emission From Relativistically Expanding Plasma
• Fast cooling synchrotron radiation in a decaying magnetic field and $\gamma$-ray burst emission mechanism
• Quasi-blackbody component and radiative efficiency of the prompt emission of gamma-ray bursts
• A theory of photospheric emission from relativistic, collimated outflows
• Evidence for a Photospheric Component in the Prompt Emission of the Short GRB120323A and its Effects on the GRB Hardness-Luminosity Relation
• Radiative transfer in ultra-relativistic outflows
• Open Questions in GRB Physics
• A Photosphere-Internal Shock Model of Gamma-Ray Bursts: Case Studies of Fermi/LAT Bursts
• A Theory of Mulicolor Black Body Emission from Relativistically Expanding Plasmas
• Photosphere emission from a hybrid relativistic outflow with arbitrary dimensionless entropy and magnetization in GRBs
• Synchrotron Origin of the Typical GRB Band Function - A Case Study of GRB 130606B
• Low Energy Spectral Index and $E_p$ evolution of Quasi-thermal Photosphere Emission of Gamma-Ray Bursts
• On the Hardness-Intensity Correlation in Gamma-Ray Burst Pulses
• The width of gamma-ray burst spectra
• Thermal Radiation from GRB Jets
• The Origin of the Prompt Emission for Short GRB 170817A: Photosphere Emission or Synchrotron Emission?
• The photospheric radiation model for the prompt emission of Gamma-ray Bursts: Interpreting four observed correlations
• Photospheric emission throughout GRB 100507 detected by Fermi
• Poynting flux dominated jets challenged by their photospheric emission
• Photospheric emission from stratified jets
• The HII Galaxy Hubble Diagram Strongly Favors $R_{\mathrm{h}}=ct$ over $\Lambda$CDM
• Evidence for jet launching close to the black hole in GRB 101219B - a Fermi GRB dominated by thermal emission
• The sharpness of gamma-ray burst prompt emission spectra
• The $E_{\mathrm{p}}$-Flux Correlation in the Rising and Decaying Phases of Gamma-Ray Burst Pulses: Evidence for Viewing Angle Effect?
• Photosphere emission in the X-Ray Flares of Swift Gamma-Ray Bursts and Implications for the Fireball Properties
• Hydrodynamic properties of gamma-ray bursts outflows deduced from thermal component
• Spectral components in the bright, long GRB 061007: properties of the photosphere and the nature of the outflow
• A new method of pulse-wise spectral analysis of Gamma-ray Bursts

Cited by in corpus (18)

• Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow
• GRB 200415A: A Short Gamma-Ray Burst from a Magnetar Giant Flare?
• MultiPulse {\it Fermi} Gamma-Ray Bursts. I. Evidence of the Transition from Fireball to Poynting-flux-dominated Outflow
• The time-resolved spectra of photospheric emission from a structured jet for gamma-ray bursts
• Thermal Components in Gamma-ray Bursts. I. How Do They Affect Non-Thermal Spectral Parameters?
• GRB 210121A: A Typical Fireball Burst Detected by Two Small Missions
• Thermal and nonthermal emission from a peculiar long-duration GRB 211211A
• The Photosphere Emission Spectrum of Hybrid Relativistic Outflow for Gamma-ray Bursts
• GRB 220426A: A Thermal Radiation-Dominated Gamma-Ray Burst
• Study of prompt emission of short gamma ray bursts using multi-color blackbody: a clue to the viewing angle
• Evidence of Photosphere Emission Origin for Gamma-Ray Burst Prompt Emission
• The Origin of the Photospheric Emission of GRB 220426A
• Spectral and Jet Properties of the Quasi-thermal Dominated GRB 210121A, GRB 210610B and GRB 221022B
• The Hardness-intensity Correlation of Photospheric Emission from a Structured Jet for Gamma-Ray Bursts
• GRB 210121A: Observation of photospheric emissions from different regimes and the evolution of the outflow
• Modeling of the Gamma Ray Burst photospheric emission: Monte Carlo simulation of the GRB prompt emission, numerical results and discussion
• A Comprehensive Study of Bright Fermi-GBM Short Gamma-Ray Bursts: II. Very Short Burst and Its Implications
• Harmonic brightness oscillations point to magnetar giant flares in rare short gamma-ray bursts