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View Full Version : Shivering magnetars...but not cold ones.



trinitree88
2011-Dec-22, 06:12 PM
The lighthouse model of pulsars, spinning off axis a bit, and sweeping a "lighthouse" beam of radiation outwards has been around for a while. It explains some things, but doesn't fit all the observations. The authors propose that a quivering magnetar, uses vibrations....a miniature and faster pulsation rate than Cepheids or SOHO helioseismology, but in a sense, analogous...to give off radiation more predictably. Shiver me timbers. pete SEE:http://arxiv.org/abs/1104.0526

antoniseb
2011-Dec-22, 06:33 PM
... in a sense, analogous...to give off radiation more predictably. ...
I like these papers that offer a plausible explanation for something odd we've been seeing in the details.

Shaula
2011-Dec-23, 07:35 AM
Hmm, wonder how that ties in with recent news that one of the pulsars that switched off a year and a half ago still hasn't come back on? Others have turned on and off. What could start them vibrating again?

noncryptic
2011-Dec-24, 04:50 PM
What could start them vibrating again?

Merely layman's speculation:

In 'normal' stars such as our sun apparently there are processes that can cause certain oscillations (solar cycle) to stop and start again (ie Maunder minimum). I think the different timescales of these phenomena in different types of stars are not a fundamental issue.

Generally speaking such behaviour is typical for complex dynamic systems. Then wrt to pulsars/magnetars etc the basic assumption for explaining these phenomena would be that those stars are not as dead as they might seem to be.

Even if pulsars are "lighthouses" then producing that beam involves a lot of energy. It seems unlikely to me that something where such amount of energy is at work is in fact a "cinder" that remains largely unchanged practically until the end of time.
If it's not dead but instead is dynamic then i think processes can be at work that produce dynamic behavior.

If pulsars do in fact produce a beam, then should it not be possible to observe effects of such a beam on the surroundings, ie shining on nebula in the vicinity of the pulsar? Then we could establish the existence of the beam even if Earth is not in its path. Have such observations been made or attempted?

trinitree88
2011-Dec-30, 06:21 PM
Hmm, wonder how that ties in with recent news that one of the pulsars that switched off a year and a half ago still hasn't come back on? Others have turned on and off. What could start them vibrating again?

Shaula.
A nearby supernova. The prompt neutrino burst carries away the majority of the energy. Ordinary matter is quite transparent to this burst, but the mean free path in degenerate matter runs several centimeters to at most a few meters. That makes a quiescent pulsar a neutrino trap, and the skin/atmosphere heats up. Recent simulations have shown that the nucleons within are bean-shaped, not spherical. Coupled with their intrinsic spin states, this suggests an axisymmetric radiation mode when that energy is released. pete

Shaula
2011-Dec-31, 08:03 AM
A nearby supernova.
Doesn't work.


Some pulsars go dark, though, and Camilo's was not the first. In the 1970s, some regular pulsars were spotted switching off for a few seconds to a few minutes, a phenomenon known as "nulling". And in the past decade, a new class of pulsars has been found , in which the silences can range from minutes to a few hours. They were dubbed rotating radio transients, or RRATs. Around the same time, a pulsar was found that pulsed for about a week and then switched off for about a month before repeating the cycle.
From New Scientist (http://www.newscientist.com/article/dn21304-astrophile-stopped-clocks-deepen-pulsar-enigmas.html)

We're gonna need a lot of supernovae.... Some of these could be rotational/precession effects, I guess. But that wouldn't work with the vibrations idea. You'd need the vibrations to keep stopping, then be restarted weekly/hourly/monthly by convenient supernovae. Implausible.