Posted on by Tammy Plotner

Stellar Superburst: Neutron Star Blows Away Model

[/caption]Imagine an event so catastrophic that it pours more energy out in three hours than the Sun does in a hundred years. Now imagine it a reality. In a study done by Yuri Cavecchi et al. (2011), they’ve witnessed a neutron star outburst which has put all computer modeling for thermodynamic explosions on extreme objects back to square one.

Apparently a strong magnetic field around accreting pulsar IGR J17480-2446 is the culprit for some areas of the star to ignite in the extreme. X-ray binary IGR J17480-2446, as a general rule, should be about one and a half times the mass of the Sun confined in an area of about 25km. This creates a strong gravitational field which extracts gas from its orbiting companion. In turn, this collects on the surface of the primary and kindles a fast, high-energy thermonuclear reaction. In a perfect scenario, this reaction would be spread over the surface evenly, but for some reason in about 10% of case studies some areas burn brighter than others. Just why this happens is a true enigma.

In order to better understand the phenomena, theoretical models were created to test out spin rates. They suggest that rapid rotation stops the burning material from spreading uniformly – much like the Coriolis force develops terrestrial hurricanes. Another hypothesis proposes these conflagrations ride on global-scale waves where one side stays cool and dim as it rises, while the other remains hot and bright. But just which one is viable in the case of this strange pulsar?

“We explore the origin of Type I burst oscillations in IGR J17480–2446 and conclude that they are not caused by global modes in the neutron star ocean. We also show that the Coriolis force is not able to confine an oscillation-producing hot-spot on the stellar surface.” says lead author Yuri Cavecchi (University of Amsterdam, the Netherlands). “The most likely scenario is that the burst oscillations are produced by a hot-spot confined by hydromagnetic stresses.”

What makes the astronomers think this way? One explanation might be the strange properties of J17480 itself. While it obeys the rules when it comes to forming bright patches during thermonuclear events, it break them when it comes to spin rates. Why does this particular star only rotate about 10 times per second when the next slowest does it at 245? This is where the magnetic field theory comes into play. Perhaps when explosions occur, it’s held in place by this invisible, yet powerful, force.

“More theoretical work is needed to confirm this, but in the case of J17480 it is a very plausible explanation for our observations”, says Cavecchi. Co-author Anna Watts further explains their new models – while interesting – might not account for all non-uniform events seen in similar situations. “The new mechanism may only work in stars like this one, with magnetic fields that are strong enough to stop the flame front from spreading. For other stars with this odd burning behavior, the old models might still apply.”

Original Information Source: Netherlands Research School for Astronomy. For Further Reading: Implications of burst oscillations from the slowly rotating accreting pulsar IGR 17480-2446 in the globular cluster Terzan 5.

9 Replies to “Stellar Superburst: Neutron Star Blows Away Model”

  1. If it is true that a black hole, neutron star or a magnetar’s magnetic spin rate and field strength determines the collimation of polar plasma emission (http://syzygyastro.hubpages.com/hub/Magnetic-Fields-and-their-Theoretical-Collimation) as gathered from the equatorial accretion disk, then it stands to reason that those spin rates slowing below the speed of light due to gravitation would then exhibit quantum effects upon those emissions and therefore potentially produce oppositely spun matter or ‘mirror matter’. Should that ‘mirror’ matter then interact due to gravitational effects it would create the tremendously explosive annihilation events as theorized/observed above?

    1. ???? I suppose I do not follow what you are saying. It does not make sense. Secondly black holes do not have magnetic fields.

      LC

      1. I thought they did have since the jets are coming out of north and south poles, but I am by NO stretch of the imagination an expert. Also, if they do create magnetic fields, wouldn’t it get sucked back in? Or does that only go for matter? Although if that’s the case Light isn’t matter its a particle right…..
        Damn my head hurts….

      2. Suppose a black hole has charge. If it is spinning there is then a current and this should generate a magnetic field, right? The problem is that on the event horizon as viewed from the outside the time rate of anything moving there slows to zero. So any charge you might try to observe very very near the horizon would be moving at a snail’s pace. So this charge would contribute little magnetic field. So charge which composes a black hole, which resides on the horizon, is frozen there. Hence there is no magnetic field.

        The magnetic fields we observe in association with black holes through jets is with the plasma around the black hole. The different transport properties of nuclei and electrons can generate charge separations and currents. However, this is outside the black hole, or at a radius larger than the radius of the event horizon.

        LC

  3. Whilst LC is [as always] quite correct, following this thread inspired me thinking what if small compact/dense object was near a spinning pulsar..

    I would posit that in the case of IGR J17480-2446, we have a basic gyroscope effect. The smaller {extremely dense} companion spinning (neutron star or white dwarf) around the primary neutron star (binary pulsar) would reduce the angular momentum of the pulsar primary star (slow its rate of rotation). However to my (admittedly limited) knowledge, two neutron stars in any proximity should not be slowing the rotation by that much (according to current theory of the forces of gravitation, ie. each of the companions must be less than the mass of the chandrasekhar limit so as not to collapse into black holes and within these bounds do not exert such force to cause such a dramatic slowing of rotation of the primary – 10 times per second is practically slow motion compared to most pulsars which are milisecond or greater (>1000 rotations per second)).

    One intriguing possibility that might be a Coriolis or dynamo like effect could be if there is two dense disks of super-hot plasma orbiting each of the neutron stars it may be exhibiting charge/magnetic field properties from the interaction of the two spinning disks of gaseous plasma behaving in a hydrodynamic state with double du-opolar magnetic charges.

    This could in turn induce dynamo effects with the interplay of two dense objects with plasma charged disks orbiting which may be generating the anomalous features observed here in IGR J17480-2446 .. (

    However one final intriguing possibility is a small black hole [bordering or < 10 solar mass] in tight orbit near the primary Neutron Primary. But this scenario doesn't seem to plausible as the black hole would likely consume the less dense object (in this case being the white dwarf or neutron primary) to exert enough force to cause reduction of angular momentum in the primary star. Or, finally, it may be just a plain smaller secondary neutron star and it is somehow exhibiting these anomalous gravity and magnetic phenomena on the Primary Neutron star? Quite intriguing mystery we got ourselves here .. Wow nice article- well done Tammy.

    Your thoughts LC ?

  4. Invisible force ”
    all we can do is see this stuff im sure if you were standing in front of a neutron star you would see this.

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