DSR in Galaxies
| Category | Progenitor | Type | Energy Mechanism | Emission Mechanism | Counterparts | References | Brief Comments | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| LF Radio | HF Radio | Microwave | Terahertz | Optical/IR | X-rays | Gamma-rays | Gravitational Waves | Neutrinos | |||||||
| Other | Dicke's Superradiance in Galaxies | Both | Dicke's Superradiance | Synch. | Yes | -- | -- | -- | -- | -- | -- | -- | -- | http://adsabs.harvard.edu/abs/2018MNRAS.475..514H | -- |
Definitions: LF Radio (3 MHz to 3 GHz); HF Radio (3 GHz to 30 GHz); Microwave (30 to 300 GHz)
Model Description
Postulated in 1953 and first detected in 1973, Dicke's Superradiance (DSR) has been invoked as one of the few “microphysical” FRB models. The aim is to explain FRBs using the atomic interactions in galaxies. DSR can occur in astrophysical settings, provided: the collection of atoms is inverted (to wit, a majority of atoms exist in higher excited states than the minority); the velocity coherence is high; and the non-coherent relaxation mechanisms occur on a timescale larger than the delay time. If one models the ISM as a cylinder of atoms, the predicted DSR emission power and timescale can fit FRB data. This is because the coherent behaviour of the DSR atoms has a timescale which scales as τ ∝ N−1 and an intensity which scales as I ∝ N2, where N is the number of entangled molecules. This model is additionally appealing since the DSR mechanism can adapt to a wide variety of FRB behaviour, and proposes no new entities/physics. Indeed, the DMs associated with FRBs fits well with the ISM required for DSR to occur. DSR also presents a mechanism through which a repeater can be explained. If a collection of molecules has DSR triggered at the same time, the intrinsic variation in the DSR timescale and time delay would give the observation of bursts at different times. The variation is because the time delay is an expectation value, and the collection of molecules being ionised at the same time is due to the entanglement, which also causes a differential in emission time. This process can happen repeatedly as population inversion will be non-inverted but swiftly restored via the ISM, which will drive more FRB pulses, and so on. The flux distribution of such a setup can be matched to FRB 121102.