Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: chris on 24/04/2017 07:59:57

Title: Could Fast Radio Bursts be the radio equivalent of a microwave MASER?
Post by: chris on 24/04/2017 07:59:57
Justin wants to know:

Fast Radio Bursts are reported by Astronomers to be the most luminous radio burst in the universe. Some articles report that the burst is powered by the equivalent energy of 500 million suns. Is this calculation assuming energy radiating equally in all directions? What if the radio burst is highly collimated like a LASER? Could FRBs be the radio equivalent of a microwave MASER?

What does everyone think?
Title: Re: Could Fast Radio Bursts be the radio equivalent of a microwave MASER?
Post by: evan_au on 24/04/2017 13:23:05
One of the characteristics of masers (and lasers) is that they have a very narrow frequency band, usually around the some metastable resonance of the lasing medium.
- In the case of the Hydrogen maser, this frequency is 1,420 GHz.
- The Stimulated Emission of Radiation (the ..SER in MASER and LASER) allows very directional bursts of radiation.

However, the MASER suggestion does not fit the observation of Fast Radio Bursts* as FRBs have an extremely wide bandwidth.
- We know that it sweeps in frequency from high to low, due to the frequency-dispersive nature of the intergalactic medium
- and lasing does not work well over wide frequency ranges.
- What we don't know is how wide the frequency range is - some have suggested that the source is some dramatic event like the implosion of a neutron star, which would produce signals ranging from radio waves through visible light and into the gamma ray region.
- Unfortunately, telescopes can only observe a fairly narrow range of frequencies in the electromagnetic spectrum, and so far there has been no clear correlation between pulses in these distant parts of the electromagnetic spectrum. 
See: https://en.wikipedia.org/wiki/Fast_radio_burst

* I am discounting the cases where FRBs have been attributed to people opening their microwave oven doors before pressing the STOP button...