Constraining the bulk Lorentz factor from the photosphere emission

Abstract

We propose a direct and model-independent method to constrain the Lorentz factor of a relativistically expanding object, like gamma-ray bursts. Only the measurements, such as thermal component of the emission, the distance and the variable time scale of the light curve, are used. If the uncertainties are considered, we will obtain lower limits of the Lorentz factor instead. We apply this method to GRB 090618 and get a lower limit of the Lorentz factor to be 22. The method can be used to any relativistically moving object, such as gamma-ray bursts, blazars, and soft gamma-ray repeaters, providing the thermal component of the emission being observed.

10 pages, 1 figure

References in corpus (7)

• Detection of a Thermal Spectral Component in the Prompt Emission of GRB 100724B
• Discovery of the nearby long, soft GRB 100316D with an associated supernova
• A new method of determining the initial size and Lorentz factor of gamma-ray burst fireballs using a thermal emission component
• The photospheric radiation model for the prompt emission of Gamma-ray Bursts: Interpreting four observed correlations
• Photosphere emission in the X-Ray Flares of Swift Gamma-Ray Bursts and Implications for the Fireball Properties
• An Observed Correlation Between Thermal and Non-Thermal Emission in Gamma-Ray Bursts
• Probing the emission physics and weak/soft population of Gamma-Ray Bursts with LOFT

Cited by in corpus (4)

• Evaluating the bulk Lorentz factors of outflow material: lessons learned from the extremely-energetic outburst GRB 160625B
• Characteristics of Long Gamma-Ray bursts in the Comoving Frame
• Detection of Prompt Fast-Variable Thermal Component in Multi-Pulse Short Gamma-Ray Burst 170206A
• $L_{\mathrm{syn}}-E_{\mathrm{syn},\mathrm{p}}-\delta$ relation in Active Galactic Nucleus Jets and Implication for the physical origin of the $L_{\mathrm{p}}-E_{\mathrm{p},\mathrm{z}}-{\Gamma }_0$ relation of Gamma-Ray Bursts