Three Glitches in a Silent Pulsar ✛
Context
Glitches—sudden speed-ups in pulsar rotation—have long been considered a hallmark of young, energetic neutron stars. But PSR J1637−4642 stood out: with a characteristic age of about 41,000 years and high luminosity, it had remained silent since its discovery in the Parkes Multibeam survey. Related studies in the archive show that glitches are studied across a wide range of pulsars, from the Crab to globular clusters, but it is precisely the 'quiet' sources that suddenly wake up that offer a rare chance to see how long stress builds up in the crust. This paper fills a gap: for the first time, PSR J1637−4642 is found to exhibit not one but three glitches, and one of them is strong enough for detailed modeling.
Methods
Observations were conducted with the 64-meter Murriyang radio telescope (Parkes, Australia) from February 2009 to October 2024. The pulsar's signal was recorded with three different receiver systems: the multibeam (1369 MHz), H-OH (1465 MHz), and the ultra-wideband UWL (704–4032 MHz). Due to the source's faintness, only 166 reliable pulse arrival times were obtained. The time series were analyzed using the PSRCHIVE and TEMPO2 packages, splitting the data into four segments around the glitch epochs. For the strongest glitch, Bayesian modeling of the aftermath was performed within the vortex creep model, using the Bilby package and the dynesty sampler.
Results
The first glitch occurred around MJD 58352 (approximately 2020) and changed the rotation frequency by 2.7×10⁻⁶—a jump of 17.5 microhertz. The second, three years later, was 1200 times weaker: only 2.2×10⁻⁹. The third, another 2.7 years later, had an intermediate strength of 2.8×10⁻⁸. Only the first glitch showed exponential recovery: the frequency partially returned over a characteristic timescale of about 100 days, but only a small fraction—1.5% of the jump—recovered. Fitting the vortex creep model yielded a superfluid moment of inertia fraction of 1.87% of the star's total moment of inertia. This value falls within the range expected for superfluid neutrons in the inner crust.
Implications
The work strengthens the standard superfluid model of glitches: a glitch occurs when vortices in the superfluid detach from lattice nuclei and transfer angular momentum to the crust. Unlike neighboring studies that often merely report a glitch, here a physical parameter—the superfluid fraction—was extracted from the aftermath. This is a rare case where a single glitch provides a quantitative estimate of a neutron star's internal structure, not just event statistics.
Future development
If the pulsar continues to be monitored, more glitches can be accumulated to test whether their size distribution follows a power law, as seen in other young pulsars. It is also important to track whether glitches with a higher recovery fraction appear, which would indicate a different vortex creep regime. In the long run, such studies could link glitch rates to core temperature and refine the equation of state of ultra-dense matter.
Impact
The results will affect models of neutron stars, the physics of superfluids under extreme conditions, and the interpretation of data from gravitational-wave detectors, where knowing how neutron stars rotate and glitch is crucial.
Next steps
Continue regular timing of PSR J1637−4642 with Murriyang to catch the next glitch and refine the distribution of intervals between events. Also, more thorough modeling of timing noise is warranted to better separate the secular trend from random wanderings.
Key open problems
In neutron star physics, an open question remains: what fraction of the moment of inertia resides in the superfluid component, and how exactly do vortices interact with the crust? This work provides a direct estimate of this fraction for one object, but does not resolve the uncertainty in pinning energy and critical lag, which affect temperature interpretation.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
This study presents an analysis of 15.5 years of observations of the pulsar PSR J1637−4642 with the Murriyang radio telescope, during which three glitches with amplitudes ranging from 2.2×10⁻⁹ to 2.7×10⁻⁶ were detected for the first time. For the strongest glitch, a Bayesian modeling of the post-glitch recovery was performed within the framework of the vortex creep model, allowing an estimate of the superfluid moment of inertia fraction of 1.9%. It is shown that even pulsars long considered stable can accumulate stress and exhibit glitch activity.
Where its strength is
A key strength is the quantitative estimate of the superfluid component fraction derived from the recovery of a single glitch, which is rarely achieved for pulsars with few recorded events. This demonstrates the possibility of extracting physical parameters of a neutron star even from limited data.
Where it could go next
- It might be interesting to compare the obtained superfluid moment of inertia fraction with predictions from the vortex trap model, which explains glitch formation through vortex dynamics in the crust. Our archive contains a detailed analysis of a paper where such a model is developed and could provide additional context for interpreting the observed post-glitch recovery.based on: Cosmic Avalanches: How Vortex Traps Shape Pulsar Glitches
- Nearby lies a study of a pulsar that is almost always quiet but exhibits rare bursts of activity. Comparing with such sources could help understand how typical the observed behavior is for PSR J1637−4642 and what mechanisms are responsible for long periods of stability.based on: A radio pulsar that is almost always silent
- It would be interesting to examine the glitch statistics of the Crab pulsar, which glitches on a relatively regular schedule. Possibly, comparing with its activity could help clarify how age and energy loss rate influence the frequency and amplitude of glitches in neutron stars.based on: The Crab Pulsar: Glitches on Schedule
Worth trying
- Apply the vortex trap model to calculate the expected superfluid moment of inertia fraction and compare it with the obtained value of 1.9%.
- Search for additional weak glitches in the archival data of PSR J1637−4642 using more sensitive algorithms to assess the full activity picture.
- Compare the glitch parameters of PSR J1637−4642 with a sample of pulsars that exhibited single glitches after long periods of quiescence to identify common patterns.
Nearby works in our archive
- A cosmic lighthouse that blinks like crazysimilarity 0.66
- A radio pulsar that is almost always silentsimilarity 0.65
- A Pulsar That Shudders with Flaressimilarity 0.64
- The Crab Pulsar: Glitches on Schedulesimilarity 0.64
- The Hidden Pulsar in a Globular Clustersimilarity 0.64
- Night Watchman for Cosmic Flashessimilarity 0.63
- Cosmic Avalanches: How Vortex Traps Shape Pulsar Glitchessimilarity 0.62
The closest work in the archive sits at 0.66 by meaning — the usual level for our corpus.
Original abstract
as written by the authors arXiv:2608.19555v1
We present the discovery and analysis of three rotational glitches in the young pulsar PSR J1637$$-$$4642. The timing observations span from 19 February 2009 to 6 October 2024 (MJD 54881$$-$$60589) from the Murriyang radio telescope of the Parkes Observatory. The first and strongest glitch occurred around MJD 58352 with a fractional frequency change of $$\Delta u/ u \sim 2.7 \times 10^{-6}$$, while two additional smaller glitches were detected at MJD 59443 and MJD 60445 with fractional changes of $$2.2 \times 10^{-9}$$ and $$2.8 \times 10^{-8}$$, respectively. Prior to this, the pulsar had shown no glitch activity since its discovery in the Parkes Multibeam survey. Only the first glitch exhibits detectable exponential recovery, with a decay timescale of $$\sim$$100 days and a small recovery fraction $$\approx 0.015$$, accompanied by a permanent increase in the magnitude of the spin-down rate. Modeling the post-glitch evolution of $$\dot{ u}$$ within the vortex-creep framework using Bayesian inference gives a superfluid moment-of-inertia fraction $$\approx 0.0187$$, consistent with the inner-crust superfluid. These results reinforce the standard superfluid glitch paradigm and demonstrate that even ``quiet'' pulsars can still host substantial glitch activity.
The weakest glitch of this pulsar changed its rotation frequency by just 14 nanohertz — equivalent to a clock's second hand speeding up by one ten-billionth of a second per year.
Key numbers
- frequency jump of the first glitch: 2.7×10⁻⁶
- frequency jump of the second glitch: 2.2×10⁻⁹
- frequency jump of the third glitch: 2.8×10⁻⁸
- superfluid moment of inertia fraction: 1.87%
- recovery time after the first glitch: about 100 days