U will not find (search pattern to be changed)

Pavel_Suslo
Pavel_Suslo
Joined: 21 Mar 21
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Topic 225137

A few words about the article:

https://arxiv.org/abs/1509.04370

U will not find what U search for. Sory my bad English and a byte provocative style, and disclaimer - I'm not a scientist.

But when I read the article and see: U will not find.

The article say, in a simple words that a neutron star (NS) is liquid. No montains are expected. Just only an ocean, but a possible wave on it. Once if there is a wave, there are two cases: more viscosity to dump the wave or more wind to shake the wave gigantic. I say wind... in vacuum... But once the NS get a non-spherical component such as a wave, it begin to emit gravitational waves (GW). The GW emission get angular momentum, so that it push on the surface of the NS, like a wind. So the wave produce the GW output, an in return GW make the waves stronger. And more, and more complexity to the story: temperature sometimes increase the viscosity, so it suppress waves. And if waves appear, they reheat the inner core of the NS and so that switch themselves off. Everything is very complex, but there is no a shadow of a simple stable candle which emit GW energy stable and have a stable P-dot (period derivation). I mean that a real NS can have a time-to-frequency diagram of a stairs down, not a slope. Moreover, most of time the NS may be invisible in GW, and if visible - emit bright, but short and heaving a very big and unpredictably unstable period of rotation derivation (P-dot).

Mike Hewson
Mike Hewson
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In other words if the

In other words if the wobbling of the neutron star material has many ways to dissipate energy, then the radiated GWs from non-axisymmetric distributions won't last long enough to be detected at E@H ? The neutron star would radiate discontinuously in the GW band and E@H would probably miss that with current methodology ? Yep, these whirly neutron stars are messy things, particularly in company, he even mentions 'pasta phases'. Well that's a downer. But, as I've said many times before, we will either detect a wave or failing that constrain the modelling. That's science though : you have to put the theories on the chopping block of observation and see which ones keep their heads .....

{ On the upside it was written by a guy from the faculty I learnt physics from : go University of Melbourne! Crikey, that's 43 years ago .... I got in when I was 17 you see .... }

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Pavel_Suslo
Pavel_Suslo
Joined: 21 Mar 21
Posts: 2
Credit: 8,000
RAC: 0

Mike Hewson написал:In

Mike Hewson wrote:
In other words if the wobbling of the neutron star material has many ways to dissipate energy

Not so simple. There are two cases:

  1. dissipate wobbling
  2. strengthen wobbling

In the 1-st case we get no any chance to see any GW. But the second case is possible. "Strengthen wobbling"-scenario act as a burst. Burst at least in some cases. It may be short but VERY bright.

Mike Hewson wrote:
then the radiated GWs from non-axisymmetric distributions won't last long enough to be detected at E@H ?

...won't last long enough to be detected at E@H using the current methodology, I mean.

The typical E@H report looks like this: https://arxiv.org/abs/2009.12260 . "We search for nearly-monochromatic signals with frequency between 20.0 Hz and 585.15 Hz and spin-down between -2.6e-9 Hz/s and 2.6e-10 Hz/s." - it say. But the two limits - 1) ...-2.6e-9 Hz/s 2) <585.15 Hz - are too much tight limits.

Mike Hewson wrote:
The neutron star would radiate discontinuously in the GW band and E@H would probably miss that with current methodology ?

Yes, we will miss the NS even if it be very bright at a short time. We cannot see burst scenarios using current methodology because they will be filtered-out. The article (1509.04370) imply that GW-emitting NS can be VERY bright. But the total energy is limited, so the brighter the NS, the shorter its "burning" time. So I mean E@H should to correct its patern which it looks for to find a really transient process.

An additional message: we need to search for a very quick NS, heaving >~700rps and emitting GWs at >~1400Hz (remember, GW have double frequency). Frequencies above 1200Hz are not good for LIGO. LIGO is good at 50..200Hz. We need to use an other detector (may me less faimous, small, but more sensitive at high freq-s).

Mike Hewson wrote:
But, as I've said many times before, we will either detect a wave or failing that constrain the modelling.

Сonstrain is a good thing, but it imply the NS emit continuously. If not, the constrain is not usable. High GW emission can slowdown the NS rapidly, so that we need to correct our software.

We expect signal "zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz" while the "BANG!" is more expectable.

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