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Register a new userThe First Glitch in a Central Compact Object Pulsar: 1E 1207.4-5209
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Since its discovery as a pulsar in 2000, the central compact object (CCO) 1E 1207.4-5209 in the supernova remnant PKS 1209-51/52 had been a stable 0.424 s rotator with an extremely small spin-down rate and weak (Bs ~ 9E10 G) surface dipole magnetic field. In 2016 we observed a glitch from 1E 1207.4-5209 of at least Delta f/f = (2.8+/-0.4)E-9, which is typical in size for the general pulsar population. However, glitch activity is closely correlated with spin-down rate fdot, and pulsars with fdot as small as that of 1E 1207.4-5209 are never seen to glitch. Unlike in glitches of ordinary pulsars, there may have been a large increase in fdot as well. The thermal X-ray spectrum of 1E 1207.4-5209, with its unique cyclotron absorption lines that measure the surface magnetic field strength, did not show any measurable change after the glitch, which rules out a major disruption in the dipole field as a cause or result of the glitch. A leading theory of the origin and evolution of CCOs, involving prompt burial of the magnetic field by fall-back of supernova ejecta, might hold the explanation for the glitch.
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We present 20 years of timing observations for 1E 1207.4-5209, the central compact object in supernova remnant PKS 1209-51/52, to follow up on our detection of an unexpected timing glitch in its spin-down. Using new XMM-Newton and NICER observations of 1E 1207.4-5209, we now find that the phase ephemeris can be well modelled by either two small glitches, or extreme timing noise. The implied magnitudes of the frequency glitches are Delta f/f = (9+-2)E-10 and Delta f/f = (3.7+/-0.7)E-10, at epochs 2010.9 and 2014.4, respectively. The updated timing solutions also rule out our previous suggestion of a large glitch in the frequency derivative fdot. No other canonical pulsar with such a small spin-down rate (fdot = -1.2E-16 Hz/s) or surface dipole magnetic field strength (B_s = 9.8E10 G) has been observed to glitch; the glitch activity parameter of 1E 1207.4-5209 is larger than that of more energetic pulsars. Alternative parameterizations that do not involve glitches can fit the data, but they have timing residuals or a second frequency derivative fddot that are orders of magnitude larger than in pulsars with similar spin-down parameters. These timing properties of 1E 1207.4-5209 further motivate the leading theory of central compact objects, that an initial B-field of normal strength was buried in the neutron star crust by fallback of supernova ejecta, suppressing the surface dipole field. The slow reemergence of the buried field may be involved in triggering glitches or excess timing noise.
The strange timing property of X-ray pulsar 1E 1207.4-5209 can be explained by the hypothesis that it is a member of an ultra-compact binary system. This paper confronts the ultra-compact assumption with the observed properties of this pulsar. The gravitational potential well of an ultra-compact binary can enlarge the corotation radius and thus make it possible for accreting material to reach the surface of the NS in the low accretion rate case. Thus the generation of the absorption features should be similar to the case of accreting pulsars. The close equality of the energy loss by fast cooling of the postsupernova neutron star and the energy dissipation needed for a wide binary evolving to an ultra-compact binary demonstrates that the ultra-compact binary may be formed in 10-100yr after the second supernova explosion. Moreover, the ultra-compact binary hypothesis can well explain the the absence of optical counterpart and the observed two black body emissions. We suggest a simple method which can test the binary nature directly with XMM-Newton and Chandra observations. We further predict that the temperature of the two black bodies should vary at different pulse periods.
We have analyzed the archival Chandra X-ray Observatory observations of the compact feature in the Small Magellanic Cloud supernova remnant (SNR) 1E 0102.2-7219 which has recently been suggested to be the Central Compact Object remaining after the supernova explosion. In our analysis, we have used appropriate, time-dependent responses for each of the archival observations, modeled the background instead of subtracting it, and have fit unbinned spectra to preserve the maximal spectral information. The spectrum of this feature is similar to the spectrum of the surrounding regions which have significantly enhanced abundances of O, Ne, & Mg. We find that the previously suggested blackbody model is inconsistent with the data as Monte Carlo simulations indicate that more than 99% of the simulated data sets have a test statistic value lower than that of the data. The spectrum is described adequately by a non-equilibrium ionization thermal model with two classes of models that fit the data equally well. One class of models has a temperature of $kTsim0.79$ keV, an ionization timescale of $sim3times10^{11},mathrm{cm}^{-3}mathrm{s}$, and marginal evidence for enhanced abundances of O and Ne and the other has a temperature of $kTsim0.91$ keV, an ionization timescale of $sim7times10^{10},mathrm{cm}^{-3}mathrm{s}$, and abundances consistent with local interstellar medium values. We also performed an image analysis and find that the spatial distribution of the counts is not consistent with that of a point source. The hypothesis of a point source distribution can be rejected at the 99.9% confidence level. Therefore this compact feature is most likely a knot of O and Ne rich ejecta associated with the reverse shock.
We report on the timing and spectral properties of the soft X-ray emission from the magnetar 1E 2259+586 from January 2013, $sim 8$ months after the detection of an anti-glitch, until September 2019, using the Neil Gehrels Swift and NICER observatories. During this time span, we detect two timing discontinuities. The first, occurring around 5 years after the April 2012 anti-glitch, is a relatively large spin-up glitch with a fractional amplitude $Delta u/ u=1.24(2)times10^{-6}$. We find no evidence for flux enhancement or change in the spectral or pulse profile shape around the time of this glitch. This is consistent with the picture that a significant number of magnetar spin-up glitches are radiatively-quiet. Approximately 1.5 years later in April 2019, 1E 2259+586 exhibited an anti-glitch with spin-down of a fractional amplitude $Delta u/ u=-5.8(1)times10^{-7}$; similar to the fractional change detected in 2012. We do not, however, detect any change to the pulse-profile shape or increase in the rms pulsed flux of the source, nor do we see any possible bursts from its direction around the time of the anti-glitch; all of which occurred during the 2012 event. Hence, similar to spin-up glitches, anti-glitches can occur silently. This may suggest that these phenomena originate in the neutron star interior, and that their locale and triggering mechanism do not necessarily have to be connected to the magnetosphere. Lastly, our observations suggest that the occurrence rate of spin-up and spin-down glitches is about the same in 1E 2259+586, with the former having a larger net fractional change.
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 ${-1.6(39) times 10^{-19},text{Hz} text{s}^{-1}}$ 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 ${Delta u/ u=2.5(1) times 10^{-12}}$, 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 $sim 50$% that another glitch will be observed in a timing array pulsar within 10 years.
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