Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe impact of glitches on young pulsar rotational evolution
211
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch sample is complete to fractional increases in spin-frequency greater than $Delta u^{90%}_{g}/ u approx 9.3 times 10^{-9}$. We measure values of the braking index, $n$, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with $n > 10$, punctuated by step changes in the spin-down rate at the time of a large glitch. The step changes are such that, averaged over the glitches, the long-term $n$ is small. We find a near one-to-one relationship between the inter-glitch value of $n$ and the change in spin-down of the previous glitch divided by the inter-glitch time interval. We discuss the results in the context of a range of physical models.
rate research
Read More
We present a timing and glitch analysis of the young X-ray pulsar PSR J0537$-$6910, located within the Large Magellanic Cloud, using 13 years of data from the now decommissioned Rossi X-ray Timing Explorer. Rotating with a spin period of 16 ms, PSR J0537$-$6910 is the fastest spinning and most energetic young pulsar known. It also displays the highest glitch activity of any known pulsar. We have found 42 glitches over the data span, corresponding to a glitch rate of 3.2 yr$^{-1}$, with an overall glitch activity rate of $8.8times 10^{-7},$yr$^{-1}$. The high glitch frequency has allowed us to study the glitch behavior in ways that are inaccessible in other pulsars. We observe a strong linear correlation between spin frequency glitch magnitude and wait time to the following glitch. We also find that the post-glitch spin-down recovery is well described by a single two-component model fit to all glitches for which we have adequate input data. This consists of an exponential amplitude $A = (7.6 pm 1.0)times 10^{-14},$s$^{-2}$ and decay timescale $tau = 27_{-6}^{+7},$d, and linear slope $m = (4.1pm 0.4)times 10^{-16},$s$^{-2},$d$^{-1}$. The latter slope corresponds to a second frequency derivative $ddot{ u} = (4.7pm 0.5) times 10^{-22},$s$^{-3}$, from which we find an implied braking index $n=7.4 pm 0.8$. We also present a maximum-likelihood technique for searching for periods in event-time data, which we used to both confirm previously published values and determine rotation frequencies in later observations. We discuss the implied constraints on glitch models from the observed behavior of this system, which we argue cannot be fully explained in the context of existing theories.
Glitches are sudden increases in the rotation rate $ u$ of neutron stars, which are thought to be driven by the neutron superfluid inside the star. The Vela pulsar presents a comparatively high rate of glitches, with 21 events reported since observations began in 1968. These are amongst the largest known glitches (17 of them have sizes $Delta u/ ugeq10^{-6}$) and exhibit very similar characteristics. This similarity, combined with the regularity with which large glitches occur, has turned Vela into an archetype of this type of glitching behaviour. The properties of its smallest glitches, on the other hand, are not clearly established. High-cadence observations of the Vela pulsar were taken between 1981 and 2005 at the Mount Pleasant Radio Observatory. An automated systematic search was carried out that investigated whether a significant change of spin frequency $ u$ and/or the spin-down rate $dot{ u}$ takes place at any given time. We find two new glitches, with respective sizes $Delta u/ u$ of $(5.55pm0.03)times10^{-9}$ and $(38pm4)times10^{-9}$. In addition to these two glitch events, our study reveals numerous events of all possible signatures (i.e. combinations of $Delta u$ and $Deltadot{ u}$ signs), all of them small with $|Delta u|/ u<10^{-9}$, which contribute to the Vela timing noise. The Vela pulsar presents an under-abundance of small glitches compared to many other glitching pulsars, which appears genuine and not a result of observational biases. In addition to typical glitches, the smooth spin-down of the pulsar is also affected by an almost continuous activity that can be partially characterised by small step-like changes in $ u$, $dot{ u,}$ or both. Simulations indicate that a continuous wandering of the rotational phase, following a red spectrum, could mimic such step-like changes in the timing residuals.
We apply theoretical spin-down models of magnetospheric evolution and magnetic field decay to simulate the possible evolution of PSR J0250+5854, which is the slowest-spinning radio pulsar detected to date. Considering the alignment of inclination angle in a 3-D magnetosphere, it is possible that PSR J0250+5854 has a high magnetic field comparable with magnetars or/and high magnetic field pulsars, if a small inclination angle is considered. Our calculations show that similar long-period pulsars tend to have a relatively low period derivative in this case. In another case of magnetic field decay, calculations also show a possible connection between PSR J0250+5854 and high dipole-magnetic field magnetars. The evolutionary path indicates a relatively high spin-down rate for similar long-period pulsars.
The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present eleven pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches ($Delta u/ u$) from our data ranges from $10^{-6}$ to $10^{-9}$. Among these glitches, three are new discoveries, being reported for the first time. We also reanalyze the largest pulsar glitch in the Crab pulsar (PSR J0534+2200) by fitting the ORT data to a new phenomenological model including the slow rise in the post-glitch evolution. We measure an exponential recovery of 30 days after the Vela glitch detected on MJD 57734 with a healing factor $Q=5.8times 10^{-3}$. Further, we report the largest glitch ($Delta u/ u = 3147.9 times 10^{-9}$) so far in PSR J1731$-$4744.
The Crab pulsar has suffered in 1975 and 1989 two glitches in which the frequency did not relaxed to the extrapolated pre-glitch value but rather spun up showing long-term changes in the frequency derivative dot Omega. This particular behaviour has been interpreted as evidence for an evolution of the torque acting upon the star. A variable torque may be related to non-canonical braking indexes, for which some determinations have been possible. We briefly analyse in this work the consistency of postulating a growth in the angle between the magnetic moment and the rotation axis as the cause of such events. We show that this hypothesis leads to the determination of the initial period, initial and present angles, according to the assumed angle growth, for young pulsars whose respective braking indices n_{obs} and jerk parameters m_{obs} are known, and some insights on the equation of state.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
