Thermal Components in Gamma-ray Bursts. I. How Do They Affect Non-Thermal Spectral Parameters?

Abstract

The spectral components of the prompt emission of gamma-ray bursts (GRBs) mainly consist of two possible origins: synchrotron (nonthermal) and photosphere (thermal). The typical spectral properties of GRBs can be modeled by a dominant nonthermal component (a Band-like function or cutoff power law), while some of them have an additional thermal component (a Planck-like function). In this paper, we investigate the effects of thermal components on the nonthermal spectral parameters. We focus on eight {\it Fermi} Gamma-ray Burst Monitor bursts of which the spectra deviate from a Band-only function, and the thermal components are significant. We sort them into thermal-subdominant Group I (e.g. GRB 110721A) and thermal-dominant Group II (e.g., GRB 090902B). Several interesting results are found assuming the spectral component is totally attributed to the nonthermal component: (i) the low-energy photon index $\alpha$ becomes harder; (ii) the peak energy $E_{\mathrm{c}}$ is significantly smaller and lies between the peak temperature of blackbody component and the peak energy of the cutoff power law + blackbody (CPL+BB) model; (iii) total flux $F$, is generally the same; (iv) the changes ($\Delta \alpha$ and $\Delta E_{\mathrm{c}}$) are positively correlated with the ratio between the thermal flux and total flux; and (v) parameter relations ($F-\alpha$, $F-E_{\mathrm{c}}$ and $E_{\mathrm{c}}$-$\alpha$) also changed prominently. The GRBs in both groups show the same results. Our analysis indicates that the thermal component is important, and it significantly affects the spectral parameters and the consequential physical interpretations.

arXiv comment33 pages, 14 figures including 61 panels, 9 tables, matches the published version in ApJS

References in corpus (65)

• The Fermi Gamma-Ray Burst Monitor
• Unsteady Outflow Models for Cosmological Gamma-Ray Bursts
• The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
• Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations
• The BATSE Gamma-Ray Burst Spectral Catalog. I. High Time Resolution Spectroscopy of Bright Bursts using High Energy Resolution Data
• Dissipative Photosphere Models of Gamma-ray Bursts and X-ray Flashes
• Gamma-ray bursts from internal shocks in a relativistic wind: temporal and spectral properties
• The Synchrotron Shock Model Confronts a `Line of Death' in the BATSE Gamma-Ray Burst Data
• Collisional mechanism for GRB emission
• Untwisting magnetospheres of neutron stars
• 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
• Spectral Properties of Blast Wave Models of Gamma-Ray Burst Sources
• The Cooling Behavior of Thermal Pulses in Gamma-Ray Bursts
• Prompt GRB emission from gradual energy dissipation
• Reconciling observed GRB prompt spectra with synchrotron radiation ?
• GRB110721A: An extreme peak energy and signatures of the photosphere
• Temporal Evolution Of Thermal Emission From Relativistically Expanding Plasma
• Quasi-blackbody component and radiative efficiency of the prompt emission of gamma-ray bursts
• Prompt high-energy emission from gamma-ray bursts in the internal shock model
• A theory of photospheric emission from relativistic, collimated outflows
• Synchrotron Radiation as the Source of Gamma-Ray Burst Spectra
• Evidence for a Photospheric Component in the Prompt Emission of the Short GRB120323A and its Effects on the GRB Hardness-Luminosity Relation
• Extremely hard GRB spectra prune down the forest of emission models
• Radiative transfer in ultra-relativistic outflows
• 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
• Observational evidence of dissipative photospheres in gamma-ray bursts
• Non-Thermal emission from the photospheres of Gamma-Ray Burst outflows. I: High frequency tails
• Time-resolved Analysis of Fermi GRBs with Fast and Slow-Cooled Synchrotron Photon Models
• Low Energy Spectral Index and $E_p$ evolution of Quasi-thermal Photosphere Emission of Gamma-Ray Bursts
• Towards a Better Understanding of the GRB Phenomenon: a New Model for GRB Prompt Emission and its effects on the New Non-Thermal L${}_{\mathrm{i}}^{\mathrm{NT}}$-E${}_{\mathrm{peak},\mathrm{i}}^{\mathrm{rest},\mathrm{NT}}$ relation
• Constraints on the Synchrotron Emission Mechanism in GRBs
• Radiation from an expanding cocoon as an explanation of the steep decay observed in GRB early afterglow light curves
• Low-energy Spectra of Gamma-ray Bursts from Cooling Electrons
• Variable jet properties in GRB110721A: Time resolved observations of the jet photosphere
• Prompt Gamma Ray Burst emission from gradual magnetic dissipation
• The Origin of the Prompt Emission for Short GRB 170817A: Photosphere Emission or Synchrotron Emission?
• Photospheric emission throughout GRB 100507 detected by Fermi
• Relativistic MHD simulations of collision-induced magnetic dissipation in Poynting-flux-dominated jets/outflows
• The emission mechanism in magnetically dominated GRB outflows
• MultiPulse {\it Fermi} Gamma-Ray Bursts. I. Evidence of the Transition from Fireball to Poynting-flux-dominated Outflow
• Significance of an excess in a counting experiment: assessing the impact of systematic uncertainties and the case with Gaussian background
• Theory of photospheric emission from relativistic outflows
• Marginally fast cooling synchrotron models for prompt GRBs
• Black-body components in Gamma-Ray Bursts spectra?
• Evidence for jet launching close to the black hole in GRB 101219B - a Fermi GRB dominated by thermal emission
• Very High Lorentz Factor Fireballs and Gamma-Ray Burst Spectra
• The time-resolved spectra of photospheric emission from a structured jet for gamma-ray bursts
• Multi-color blackbody emission in GRB 081221
• "Double-tracking" Characteristic of the Spectral Evolution of GRB 131231A: Synchrotron Origin?
• Photospheric Emission in Gamma-Ray Bursts
• Monte Carlo simulations of the photospheric emission in GRBs
• Gamma-ray Bursts Induced by Turbulent Reconnection
• Synchrotron emission in GRBs observed by Fermi: Its limitations and the role of the photosphere
• Probing Curvature Effects in the Fermi GRB 110920
• Polarization signature of gamma-ray bursts from fragmented fireballs
• Physics of non-dissipative ultrarelativistic photospheres
• Photospheric Emission in the Joint GBM and Konus Prompt Spectra of GRB 120323A
• Comptonization of photons near the photosphere of relativistic outflows
• A new method of pulse-wise spectral analysis of Gamma-ray Bursts
• GRB 990413: Insight into the thermal phase evolution
• Spreading of ultrarelativistically expanding shell: an application to GRBs
• Detection of the thermal component in GRB 160107A

Cited by in corpus (23)

• Bayesian Time-Resolved Spectroscopy of Multi-Pulsed GRBs: Variations of Emission Properties amongst Pulses
• "Double-tracking" Characteristic of the Spectral Evolution of GRB 131231A: Synchrotron Origin?
• Testing High-latitude Curvature Effect of Gamma-Ray Bursts with {\it Fermi} Data: Evidence of Bulk Acceleration in Prompt Emission
• Nature of the ultrarelativistic prompt emission phase of GRB 190114C
• On Spectral Peak Energy of Swift Gamma-Ray Bursts
• The Photosphere Emission Spectrum of Hybrid Relativistic Outflow for Gamma-ray Bursts
• Prevalence of Extra Power-Law Spectral Components in Short Gamma-Ray Bursts
• Dissecting the Energy Budget of a Gamma-Ray Burst Fireball
• Evolution Patterns of the Peak Energy in the GRB Prompt Emission
• GRB 220426A: A Thermal Radiation-Dominated Gamma-Ray Burst
• MAGICal GRB 190114C: Implications of cutoff in the spectrum at sub-$GeV$ energies
• GRB 190829A -- A Showcase of Binary Late Evolution
• A Cosmological Fireball with Sixteen-Percent Gamma-Ray Radiative Efficiency
• Evidence of Photosphere Emission Origin for Gamma-Ray Burst Prompt Emission
• Revisiting the Spectral-Energy Correlations of GRBs with {\it Fermi} Data I: Model-wise Properties
• Overall Spectral Properties of Prompt Emissions with Diverse Segments in Swift/BAT Short Gamma-ray Bursts
• Standard GRB Spectral Models "Misused"?
• Gamma-Ray Burst prompt emission from the synchrotron radiation of relativistic electrons in a rapidly decaying magnetic field
• The white dwarf binary merger model of GRB 170817A
• Self-Similarities and Power-laws in the Time-resolved Spectra of GRB 190114C, GRB 130427A, GRB 160509A, and GRB 160625B
• Time-resolved Spectral Properties of Fermi-GBM Bright Long Gamma-Ray Bursts
• GRB 190114C: Fireball Energy Budget and Radiative Efficiency Revisited
• Revise thermal winds of remnant neutron stars in gamma-ray bursts