Astronomers detect glitch in a millisecond pulsar

Astronomers detect glitch in a millisecond pulsar
Timing residuals for PSR J0613−0200 (purple stars: EPOS 1390 MHz green squares: AFB 1400 MHz blue triangles: AFB 600 MHz red circles: AFB 400 MHz black crosses: DR1 including earlier EBPP 1410 MHz). Credit: arXiv:1606.04098 [astro-ph.HE]

(Phys.org)—European astronomers have uncovered evidence of a small glitch in the spin of a millisecond pulsar. According to a research paper published on June 13 on arXiv.org, the pulsar, designated PSR J0613-0200, exhibits sudden changes in spin frequency, known as timing glitches. It is so far the smallest glitch size recorded and the second detection of a glitch in a millisecond pulsar to date.

Millisecond pulsars have highly stable rotation, thus they are used as extremely precise clocks in timing experiments, and the most stable are used as probes of space-time in pulsar timing array (PTA) experiments. PSR J0613-0200 in particular, is used in gravitational wave searches with pulsar timing arrays.

Recently, a team of European researchers, led by James McKee of the Jodrell Bank Centre for Astrophysics, U.K., detected the in PSR J0613-0200, using data from four different telescopes across Europe. For their study, the astronomers employed the Lovell Telescope at Jodrell Bank in the U.K., the Nançay Radio Telescope in France, the Effelsberg Radio Telescope in Germany, and the Westerbork Synthesis Radio Telescope in the Netherlands.

According to the scientists, the small glitch was easy to detect with a data set covering a long baseline. They noted that during a detailed analysis of the available data, the effect of the glitch was easily removed without loss of timing precision and concluded that this anomaly does not affect the timing stability of this and other pulsars studied in PTA experiments.

"As the glitch is small and the red noise of the pulsar is not well-defined, it is therefore likely that potential unmodeled glitches outside the timing baseline for other PTA pulsars have no significant effect on timing array sensitivity," the researchers wrote.

The team is convinced that the observed anomaly in PSR J0613-0200 is, indeed, a glitch and rules out other possibilities, such as magnetospherically induced variations in rotation and pulse shape, or a gravitational wave burst with memory, caused by a merger of a supermassive black hole binary.

"A magnetospherically induced change in pulse shape related to a change in frequency derivative was considered as an alternative [explanation]... but no significant change of the pulse profile associated with the glitch was observed," the paper reads.

When it comes to the 'burst with memory' theory, the researchers concluded that although the change in spin-down rate is consistent with zero, the small glitch is still relatively too large for this scenario to take this possibility into account.

McKee and his team predict that for the current set of millisecond pulsars included in the PTA experiment, there is a probability of about 50 percent that another glitch will be observed in a timing array pulsar within 10 years. However, it won't be an easy task.

"For future glitches in PTA pulsars, only the pre-glitch data would be usable until sufficient time had passed for the post-glitch spin parameters to be measured, or for any post-glitch pulse profile variation to be recognized in the case of a magnetospheric variation," they concluded.

The research confirmed that glitches are very rare in millisecond pulsars. The results presented in the paper could also encourage the scientific community to conduct further studies regarding the difference between the number of glitches in millisecond pulsars and the general pulsar population.


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More information: A glitch in the millisecond pulsar J0613-0200, arXiv:1606.04098 [astro-ph.HE] arxiv.org/abs/1606.04098

Abstract
We present evidence for a small glitch in the spin evolution of the millisecond pulsar J0613−0200, using the EPTA Data Release 1.0, combined with Jodrell Bank analogue filterbank TOAs recorded with the Lovell telescope and Effelsberg Pulsar Observing System TOAs. A spin frequency step of 0.82(3) nHz and frequency derivative step of −1.6(39)×10−19Hz s−1 are measured at the epoch of MJD 50888(30). After PSR B1821−24A, this is only the second glitch ever observed in a millisecond pulsar, with a fractional size in frequency of Δν/ν=2.5(1)×10−12, which is several times smaller than the previous smallest glitch. PSR J0613−0200 is used in gravitational wave searches with pulsar timing arrays, and is to date only the second such pulsar to have experienced a glitch in a combined 886 pulsar-years of observations. We find that accurately modelling the glitch does not impact the timing precision for pulsar timing array applications. We estimate that for the current set of millisecond pulsars included in the International Pulsar Timing Array, there is a probability of ∼50% that another glitch will be observed in a timing array pulsar within 10 years.

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Jun 17, 2016
The glitch is in the guesses surrounding these pulsars.

Jun 17, 2016
Sometimes the aliens have to add a leap glitch, like we add a leap second every few years.

Jun 17, 2016
Wait - (After reading the abstract) this only the second millisecond pulsar glitch they have ever observed?!?

Jun 17, 2016
Yeah, it makes sense. Such a glitch indicates that there is unbalanced mass shifting around on the pulsar's surface. That can't happen often, and I expect it won't last long (astronomically speaking- maybe years, maybe thousands of years, but not millions). Maybe something fell onto it.

Jun 17, 2016
Apparently it extended from about 2000 to about 2010 in calendar figures.

That would tend to rule out gravitational lensing pretty strongly.

Jun 17, 2016
Apparently it extended from about 2000 to about 2010 in calendar figures.

That would tend to rule out gravitational lensing pretty strongly.

Okay, I get it now. For some reason I thought that "glitch" was for just one or a very of the millisecond pulses. I see now it is a repetitive feature..

Jun 17, 2016
Apparently it extended from about 2000 to about 2010 in calendar figures.

That would tend to rule out gravitational lensing pretty strongly.
Okay, I get it now. For some reason I thought that "glitch" was for just one or a very of the millisecond pulses. I see now it is a repetitive feature..
We good, but we not that good yet. ;)

Jun 18, 2016
Da Schneib suggested
Such a glitch indicates that there is unbalanced mass shifting around on the pulsar's surface
As a neutron star then well into homogeneous mass distribution aside from wave fluctuation, so pretty much doubt it as it would take mere mS when first absorbed into fluidic like neutron mass re immense gravitation

Da Schneib added
Maybe something fell onto it
Yes Indeed :-)

Expect it far more likely & as per my last para may suggest any no of orbital objects, subject to drag/tidal forces, suffering "structural mishap" fall in at any time & absorbed in a fluid like manner.

ie From disparate atoms to neutron "soup" with consequent ripples subsequently affecting rotational dynamics just long enough to detect, mass permitting.

Putting aside random walk issues re timing noise, I wonder if there is a phase/polarisation correlation that might enable one to infer an equivalent neutron fluidic viscosity along with existing perturbation data ?

Jun 18, 2016
Putting aside random walk issues re timing noise, I wonder if there is a phase/polarisation correlation that might enable one to infer an equivalent neutron fluidic viscosity along with existing perturbation data ?
If there's any issue with any of the parameters then it will "give very specific systematic signatures in plots of the timing residuals," – e.g.,Pulsar Timing (I don't know about 'neutron fluidic viscosity,' maybe it would affect the Δ_E parameter? But it should be visible in the plot if it affects the phase...)

Jun 18, 2016
Protoplasmix (Px) with a really good link, thanks
If there's any issue with any of the parameters then it will "give very specific systematic signatures in plots of the timing residuals," http://www.cv.nra...ing.html
I see the para re quote as it can offer representation re variance & phase referred as rotational in link's para 2 allows some internal exploration of core re data spread & thus refinement dependent upon our instrument's resolution, great for that focus but, see 1.

Px says
I don't know about 'neutron fluidic viscosity,' maybe it would affect the Δ_E parameter?
Please clarify your Δ_E - is orbital Δ gravitational potential Energy flux ?

I'm musing on fluid like nature of neutron mass perturbed via in-fall, acting similar to nuclear isomer metastability but, surface effect Eg nuclear isomers

Px says
..should be visible in the plot..
But, surely not during

1. a single revolution (yet) ?

Very "fine" indeed

Jun 18, 2016
Da Schneib suggested
Such a glitch indicates that there is unbalanced mass shifting around on the pulsar's surface
As a neutron star then well into homogeneous mass distribution aside from wave fluctuation, so pretty much doubt it as it would take mere mS when first absorbed into fluidic like neutron mass re immense gravitation
Two notes here:
1. The outer parts of the neutron star have the highest moment of inertia, therefore are the place where an inhomogenetity is most likely to cause a rotational glitch, or where the smallest inhomogeneity can cause the most effect.
2. I'd expect your arguments to militate toward greater homogeneity deeper in the interior.

So we're left with any masscon that can glitch the rotation being more likely the farther out from the center, from two arguments, moment of inertia and homogeneity.

[contd]

Jun 18, 2016
[contd]
I merely made the guess that it's therefore the least unlikely hypothesis that the masscon exists on the surface.

Expect it far more likely & as per my last para may suggest any no of orbital objects, subject to drag/tidal forces, suffering "structural mishap" fall in at any time & absorbed in a fluid like manner.
Your apparent notion of the whole neutron star being homogenous doesn't fit with the mainstream. See the Wikipedia article: https://en.wikipe...tructure

Another point is, if such infalls are "absorbed in a fluid like manner," where do masscons that survive for ten years come from?

Putting aside random walk issues re timing noise,
The data from the other neutron stars used in the study negates this possibility.

I wonder if there is a phase/polarisation correlation that might enable one to infer an equivalent neutron fluidic viscosity along with existing perturbation data?
Not sure what you have in mind here.

Jun 18, 2016
Px says
..should be visible in the plot..
But, surely not during

1. a single revolution (yet) ?

Very "fine" indeed
According to the paper it's not a single revolution, it's over a period of ten years or so. You can see that from the chart at the beginning of this article (which was taken from the paper). The "glitch" starts in late 1998 and lasts until 2010.

Jun 18, 2016
The "glitch" starts in late 1998 and lasts until 2010.

Alien galactic GPS system sometimes need a little adjustment, since stars move about.

Jun 19, 2016
Da Schneib says
1. The outer parts of the neutron star have the highest moment of inertia, therefore are the place where an inhomogenetity is most likely to cause a rotational glitch, or where the smallest inhomogeneity can cause the most effect
Sure but,

Q1 Why *should* there be any lasting more than even a few mS, *other* than from in-falling of mass sufficient to perturb ?

Da Schneib adds
...toward greater homogeneity deeper in the interior
Perhaps, though in my opinion the jury is still out re other sub-atomic particle distributions at/near core but, likely to be even shorter lived

Da Schneib says
So we're left with any masscon that can glitch the rotation being more likely the farther out from the center..
Sure but, *only* if there is a chance of non-homogeneous particle distribution lasting ie *other* than by transient in-falling ie Unlikely

My view; your 1st speculation Far less likely than your 2nd re in-falling which I concur with.

Cont

Jun 19, 2016
Continued @Da Schneib who says
I merely made the guess that it's therefore the least unlikely hypothesis that the masscon exists on the surface
I can read intent :-) Its not any attack you need to enter a defensive posture - its a dialectic which I hope you appreciate has convergence intent. I'm all for speculation where there's a grounding & guesses are fine too :-)

Da Schneib says
Your apparent notion of the whole neutron star being homogenous doesn't fit with the mainstream
No & apologies, didn't wish you to infer I meant the "whole" entity was homogeneous 'all the way down'. You know we both did uni physics, so grant some memory of that, ie strong/weak force interactions at/near core offering shell like structures similar to nuclear isomers - which I did touch on...

Da Schneib asks
... if such infalls are "absorbed in a fluid like manner," where do masscons that survive for ten years..
No, my point is unlikely to last long & if so why ?

Cont

Jun 19, 2016
Continued @ Da Schneib who says
Putting aside random walk issues re timing noise,
The data from the other neutron stars used in the study negates this possibility
Sure, thats one reason I did write "Putting aside", dealt with, moving on...

Da Schneib asks
I wonder if there is a phase/polarisation correlation that might enable one to infer an equivalent neutron fluidic viscosity along with existing perturbation data?
Not sure what you have in mind here
F1. We know from Quantum Mechanics (QM) two key issues; Uncertainty & Wave like properties. Therefore appropriate to infer any number of fluidic like attributes at any part of the Neutron's Star structure very likely.

I also speculate re my sentence F1 any notion of a stable outer shell subject to virtually instantaneous local transitions from fluidic to superfluidic to solid & back. Especially so as latter highly unlikely to be any conventional solid anywhere near our experience.

Cont

Jun 19, 2016
Continued @Da Schneib
Therefore likelihood of (even transitional) fluid properties appropriate to seek quantification. Thats what we do from Physics to Electronic Engineering as it enhances pursuit to know details ie Adding to various mathematical models where one or more of them has their extrapolation confirmed by good instrumentation.

So when you offer
According to the paper it's not a single revolution, it's over a period of ten years or so
Yes, illustrates limitation gaining high res polarisation data of effect of rotational wobble re emitted signal

ie. If there was high timing resolution to acquire data from just 1 sweep AND fourier composite over multiple sweeps, can infer higher probability allowing delineation of

1. Local mass concentration
2. Tidal force
3. Other

Da Schneib adds
. "glitch" starts in late 1998 and lasts until 2010
Sure & why, as keen observers of value/limitations of instrumentation, why 1 revolution data useful at high res

Jun 19, 2016
Adding to my last posts re replies to Da Schneib re clarification of intent behind my questions & in respect of my comment some 16Hrs ago "I'm musing on fluid like nature of neutron mass perturbed via in-fall, acting similar to nuclear isomer metastability but, surface effect Eg nuclear isomers"

Hope audience understand "musing" akin to speculation similar vein to Da Schneib's guess & all fine. Normal process as part critiquing/adding to base hypothesis or means to augment aspect of existing hypotheses

In line with that overall & avoid potential divergence re breadth of my posts:-

i. My point re polarisation resolution aimed to address instrumentation re just 1 sweep as the cone of emission passes across our field of view. In that short transition, if we've enough instrument resolution we should gain more information & may be useful to refine even incrementally, any current models

ii. Also useful to include phase jitter (by fourier too) re instrumentation in i.

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