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PetTastic
2018-Nov-30, 03:59 PM
Could gravitational wave detectors be sensitive to neutrino pressure?

A while back in order to explain asymmetric explosions, there was the suggestion that core collapse supernovas may not collapse in one go but undergo many collapse rebound cycles.
It was suggested that a sensitive enough neutrino detector might see many busts of neutrinos getting faster and more powerful as the star takes days to collapse inwards, follow by a rapid decay in rate and powers as the outer layers of the star blow off.
In my notes the the expected pattern was described as a chirp. The same word is used in gravitational wave results.

Shaula
2018-Nov-30, 05:13 PM
Could gravitational wave detectors be sensitive to neutrino pressure?

A while back in order to explain asymmetric explosions, there was the suggestion that core collapse supernovas may not collapse in one go but undergo many collapse rebound cycles.
It was suggested that a sensitive enough neutrino detector might see many busts of neutrinos getting faster and more powerful as the star takes days to collapse inwards, follow by a rapid decay in rate and powers as the outer layers of the star blow off.
In my notes the the expected pattern was described as a chirp. The same word is used in gravitational wave results.
A chirp is just a signal in which the frequency increases or decreases over time, it is a really common kind of signal. It is used in communications, radar systems, sonar systems etc. You see them in animals using echolocation, atmospheric 'whistles', birdsong, earthquakes, turbulence etc.

LIGO is most sensitive to frequencies around 1-100Hz. Did these proposed cycles get up to that kind of frequency? I'm not sure if the mechanism for neutrino generation in supernovae is so sensitive or reponsive to density that it would modulate in that way.

PetTastic
2018-Dec-02, 12:02 PM
A chirp is just a signal in which the frequency increases or decreases over time, it is a really common kind of signal. It is used in communications, radar systems, sonar systems etc. You see them in animals using echolocation, atmospheric 'whistles', birdsong, earthquakes, turbulence etc.

LIGO is most sensitive to frequencies around 1-100Hz. Did these proposed cycles get up to that kind of frequency? I'm not sure if the mechanism for neutrino generation in supernovae is so sensitive or reponsive to density that it would modulate in that way.

If I had access to the paper I did not keep a link.
From my notes it was about a mechanism for aligned asymmetric supernova. Hundreds of rebound shock-waves heating the baulk of the star amplifying environmental interactions.

At the time, I was more interested in the potential for the rebound shock waves to carry angular momentum outwards.

I think what I saw described a mechanism and was very short on numbers.

I am guessing the forming neutron star would be only km across and capable of millisecond behaviours. The massive star could be a light minute across or more.

If the drop in supporting pressures travelling outwards was limited to the speed of sound in the star, then the chirp could be days long??

At what point would the energy carried outwards by the shock-waves halt the collapse of the baulk of the star and explode it outwards?
I would guess the 100Hz range is possible, if the star was the right size, right composition .......

Jens
2018-Dec-02, 01:05 PM
It's funny, but working as a press officer at a scientific institute you come across lots of different papers. I actually wrote a press release (http://www.riken.jp/en/pr/press/2017/20170622_2/) for a paper about neutrino-driven supernovae explosions.

Shaula
2018-Dec-02, 04:43 PM
I would guess the 100Hz range is possible, if the star was the right size, right composition .......
I would guess it probably isn't. Which is why we kind of need a paper with some actual physics in to get much further!

I'm also not sure how you'd get enough neutrino flux to affect the results from LIGO without every neutrino detector across the planet saturating.

PetTastic
2018-Dec-03, 04:56 PM
I would guess it probably isn't. Which is why we kind of need a paper with some actual physics in to get much further!

I'm also not sure how you'd get enough neutrino flux to affect the results from LIGO without every neutrino detector across the planet saturating.

It is tricky to see how such a mechanism could product bursts of neutrinos shorter than a seconds that would otherwise all merge together at higher frequencies.

Am I right in thinking that there are a large number of collisions inside a neutrino detector that could transfer momentum but only tiny fraction produce a detectable result like some sort of beta decay?

Shaula
2018-Dec-03, 05:11 PM
Am I right in thinking that there are a large number of collisions inside a neutrino detector that could transfer momentum but only tiny fraction produce a detectable result like some sort of beta decay?
The momentum only interactions are neutral current interactions (since neutrinos only really interact via the weak force). I had a quick read around and found that the Mini-Boone experiment had the branching fraction for neutrino-nucleus interactions as 18% for the neutral current. CERN SPS had a figure of about 30% (it is pretty energy dependent). Its not an area I am overly familiar with but I don't think that charged current interactions are particularly rare compared to neutral current interactions. Neutrino interactions really are just that low a cross section.

PetTastic
2018-Dec-04, 02:51 PM
I got a few emails suggesting the 'rebound' was more likely the neutron star adjusting shape as it grows and spins-up. https://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Starquake
This sounds a bit more plausible a source of short pulses of neutrinos generated via gamma pulses reacting with collapsing star.