The paper discusses the unsteady outflow models for cosmological gamma-ray bursts (GRBs). The authors, M.J. Rees and P. Mészáros, argue that the energy release in a GRB event is not instantaneous but occurs over a finite duration, with the mean Lorentz factor \(\Gamma\) fluctuating around its average value. This variability allows for the formation of internal shocks within the outflowing material, which can convert a significant fraction of the kinetic energy into non-thermal radiation, such as gamma rays. The key points are: 1. **Event Duration and Energy Release**: The energy release in a GRB event is typically over a few seconds, but the dynamical timescale of a compact stellar-mass object is much shorter (\(\sim 10^{-3}\) seconds). This variability allows for the formation of internal shocks. 2. **Lorentz Factors and Internal Shocks**: If \(\Gamma\) fluctuates by a factor of \(\sim 2\) around its mean value, relative motions within the outflowing material can become relativistic, leading to internal shocks. For \(\Gamma \sim 10^2\), dissipation occurs outside the photosphere, converting a substantial fraction of the outflow energy into non-thermal radiation. 3. **Unsteady Outflow Models**: The authors propose that the outflow is not steady but varies on timescales ranging from \(10^{-3}\) to 10 seconds. This variability allows for the efficient conversion of kinetic energy into gamma rays through internal shocks, even with lower values of \(\eta\) (the ratio of radiation and magnetic energy to rest mass). 4. **Magnetic Fields**: Ultra-intense magnetic fields, either in young pulsar models or in compact binary coalescences, can play a crucial role in ensuring efficient cooling through synchrotron emission. Even if the magnetic field is not dynamically significant, it can still ensure effective cooling. 5. **Phenomenology and Discussion**: The unsteady and magnetized outflow model can accommodate a larger amount of baryonic contamination while still producing a nonthermal gamma-ray burst. The complex time structure of observed GRBs may be due to the development of internal shocks subject to irregularities in the outflow. The paper concludes that the short timescales and adequate efficiencies required for GRBs do not need such high values of \(\eta\) as earlier models, and the time structure can be complex, influenced by the time history of the Lorentz factor. The broad range of burst morphologies could be due to different Lorentz factors or internal variability along the axis and boundaries of jets.The paper discusses the unsteady outflow models for cosmological gamma-ray bursts (GRBs). The authors, M.J. Rees and P. Mészáros, argue that the energy release in a GRB event is not instantaneous but occurs over a finite duration, with the mean Lorentz factor \(\Gamma\) fluctuating around its average value. This variability allows for the formation of internal shocks within the outflowing material, which can convert a significant fraction of the kinetic energy into non-thermal radiation, such as gamma rays. The key points are: 1. **Event Duration and Energy Release**: The energy release in a GRB event is typically over a few seconds, but the dynamical timescale of a compact stellar-mass object is much shorter (\(\sim 10^{-3}\) seconds). This variability allows for the formation of internal shocks. 2. **Lorentz Factors and Internal Shocks**: If \(\Gamma\) fluctuates by a factor of \(\sim 2\) around its mean value, relative motions within the outflowing material can become relativistic, leading to internal shocks. For \(\Gamma \sim 10^2\), dissipation occurs outside the photosphere, converting a substantial fraction of the outflow energy into non-thermal radiation. 3. **Unsteady Outflow Models**: The authors propose that the outflow is not steady but varies on timescales ranging from \(10^{-3}\) to 10 seconds. This variability allows for the efficient conversion of kinetic energy into gamma rays through internal shocks, even with lower values of \(\eta\) (the ratio of radiation and magnetic energy to rest mass). 4. **Magnetic Fields**: Ultra-intense magnetic fields, either in young pulsar models or in compact binary coalescences, can play a crucial role in ensuring efficient cooling through synchrotron emission. Even if the magnetic field is not dynamically significant, it can still ensure effective cooling. 5. **Phenomenology and Discussion**: The unsteady and magnetized outflow model can accommodate a larger amount of baryonic contamination while still producing a nonthermal gamma-ray burst. The complex time structure of observed GRBs may be due to the development of internal shocks subject to irregularities in the outflow. The paper concludes that the short timescales and adequate efficiencies required for GRBs do not need such high values of \(\eta\) as earlier models, and the time structure can be complex, influenced by the time history of the Lorentz factor. The broad range of burst morphologies could be due to different Lorentz factors or internal variability along the axis and boundaries of jets.