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Magnetars sometimes exhibit mysterious ‘glitches’, during which angular momentum is transferred between the star’s outer and inner crusts, and involving a sudden spin-up of the star; here X-ray timing observations reveal a sudden spin-down, or ‘anti-glitch’ in a magnetar. An 'anti-glitch' from a go-slow magnetar Hundreds of glitches observed in the emission of radio pulsars and magnetars — strongly magnetic neutron stars emitting X- and γ-rays — have involved a sudden spin-up, or increase in the surface angular velocity. Glitches are thought to arise when angular momentum is transferred between the solid outer crust and the superfluid component of the inner crust. This paper reports the first observation of an 'anti-glitch', a sudden spin-down event, in the magnetar 1E 2259+586. The event coincided with an X-ray flare and X-ray bursts similar to those seen during some previous magnetar spin-up glitches, suggesting an origin in the stellar interior rather than the magnetosphere. Current models of neutron star spin-down do not predict such behaviour. Magnetars are neutron stars with X-ray and soft γ-ray outbursts thought to be powered by intense internal magnetic fields 1 . Like conventional neutron stars in the form of radio pulsars, magnetars exhibit ‘glitches’ during which angular momentum is believed to be transferred between the solid outer crust and the superfluid component of the inner crust 2 , 3 , 4 . The several hundred observed glitches in radio pulsars 5 , 6 and magnetars 7 have involved a sudden spin-up (increase in the angular velocity) of the star, presumably because the interior superfluid was rotating faster than the crust. Here we report X-ray timing observations of the magnetar 1E 2259+586 (ref. 8 ), which exhibited a clear ‘anti-glitch’—a sudden spin-down. We show that this event, like some previous magnetar spin-up glitches 9 , was accompanied by multiple X-ray radiative changes and a significant spin-down rate change. Such behaviour is not predicted by models of neutron star spin-down and, if of internal origin, is suggestive of differential rotation in the magnetar, supporting the need for a rethinking of glitch theory for all neutron stars 10 , 11 .

Four cattle, sheep, ponies and donkeys were fed dehydrated lucerne, early-cut hay, later-cut hay or barley straw in a Latin square-based design for four periods of 35d. In the first sub-period animals were fed the diets ad libitum (1–21d) and in the second sub-period they were fed the same diet restricted to 0·75 of ad libitum intake (days 22–35). Measurements of forage intake, apparent digestibilities and gastrointestinal mean retention times (MRT) were made in the last 7d of each sub-period. Differences between species in voluntary DM intake (VDMI; g/kg live weight LW)0·75 and g/LW) were greatest on the lucerne and least on barley straw. Cattle VDMI (g/kg LW0·75) compared with intake of the other species was > ponies > sheep > donkeys on lucerne. On barley straw VDMI (g/kg LW0·75) of cattle compared with intake of the other species was = donkey = ponies > sheep. VDMI of hays were intermediate between the lucerne and straw forages. Apparent digestibilities of DM, organic matter (OM), neutral-detergent fibre (NDF) and acid-detergent fibre (ADF) of the lucerne and hays were higher in the ruminants than in the equids. Effect of feeding level was not significant. Gastrointestinal MRT was shorter in the equids than in the ruminants. On straw diets donkeys showed similar apparent digestibilities of feed components to those of the cattle, whilst apparent digestibility of the straw diet by the ponies was lowest. Results are discussed in relation to evolutionary differences in feeding and digestion strategy associated with fore- or hind-gut fermentation in ruminants and equids.

Four donkeys and four ponies were fed molassed dehydrated alfalfa or oat straw, either ad libitum or restricted to about 70 % ad libitum intake in a Latin-square design for four periods of 21 d. Measurements of apparent digestibility and gastrointestinal transit time were made on the last 7 d of each period. When the forages were provided ad libitum, all animals ate significantly (P<0.01) more of the alfalfa than of the oat straw. Ponies consumed significantly (P = 0.007) more of both diets per unit live weight than donkeys. Higher apparent digestibilities of dietary DM, energy and fibre fractions were seen in donkeys, at both levels of feeding, compared with the ponies. This partly compensated for the lower intakes by the donkeys when fed ad libitum. When intake of alfalfa was restricted, the apparent digestibility of DM was higher compared with the corresponding values when fed ad libitum, but the reverse was true for straw. This may be because restriction of a low-quality diet reduced selection of the more digestible parts of the forage. Donkeys and ponies consumed more energy and protein than required when fed alfalfa ad libitum. Both oat straw treatments provided insufficient protein to meet the predicted requirements of ponies and donkeys. Straw intakes ad libitum exceeded the estimated energy requirement for ponies by 34–51 %, but donkey energy requirements were only just met. When the amount of straw offered was restricted, 78–90 % of the estimated energy requirement for donkeys was met compared with 90–105 % for the ponies.

Since its discovery, 1E 1048.1\\(-\\)5937 has been one of the most active magnetars, both in terms of radiative outbursts, and changes to its spin properties. Here we report on a continuing monitoring campaign with the Neil Gehrels Swift Observatory X-ray Telescope in which we observe two new outbursts from this source. The first outburst occurred in 2016 July, and the second in 2017 December, reaching peak 0.5-10 keV absorbed fluxes of \\(3.2^{+0.2}_{-0.3}\\times 10^{-11}\\) erg s\\(^{-1}\\) cm\\(^{-2}\\) and \\(2.2^{+0.2}_{-0.2}\\times10^{-11}\\) erg s\\(^{-1}\\) cm\\(^{-2}\\), respectively, factors of \\(\\sim\\)5 and \\(\\sim 4\\) above the quiescent flux. Both new outbursts were accompanied by spin-up glitches with amplitudes of \\(\\Delta\\nu= 4.47(6)\\times10^{-7}\\) Hz and \\(\\Delta\\nu= 4.32(5)\\times10^{-7}\\) Hz, respectively. Following the 2016 July outburst, we observe, as for past outbursts, a period of delayed torque fluctuations, which reach a peak spin-down of \\(1.73\\pm0.01\\) times the quiescent rate, and which dominates the spin evolution compared to the spin-up glitches. We also report an observation near the peak of the first of these outbursts with NuSTAR in which hard X-ray emission is detected from the source. This emission is well characterized by an absorbed blackbody plus a broken power law, with a power-law index above \\(13.4\\pm0.6\\) keV of \\(0.5_{-0.2}^{+0.3}\\), similar to those observed in both persistent and transient magnetars. The hard X-ray results are broadly consistent with models of electron/positron cooling in twisted magnetic field bundles in the outer magnetosphere. However the repeated outbursts and associated torque fluctuations in this source remain puzzling.

We report on the aftermath of a magnetar outburst from the young, high-magnetic-field radio pulsar PSR J1119-6127 that occurred on 2016 July 27. We present the results of a monitoring campaign using the Neil Gehrels Swift X-ray Telescope, NuSTAR, and XMM-Newton. After reaching a peak luminosity of ~300 times the quiescent luminosity, the pulsar's X-ray flux declined by factor of ~50 on a time scale of several months. The X-ray spectra are well described by a blackbody and a hard power-law tail. After an initial rapid decline during the first day of the outburst, we observe the blackbody temperature rising from kT = 0.9 keV to 1.05 keV during the first two weeks of the outburst, before cooling to 0.9 keV. During this time, the blackbody radius decreases monotonically by a factor of ~4 over a span of nearly 200 days. We also report a heretofore unseen highly pulsed hard X-ray emission component, which fades on a similar timescale to the soft X-ray flux, as predicted by models of relaxation of magnetospheric current twists. The previously reported spin-up glitch which accompanied this outburst was followed by a period of enhanced and erratic torque, leading to a net spin-down of \\(\\sim3.5\\times10^{-4}\\) Hz, a factor of ~24 over-recovery. We suggest that this and other radiatively loud magnetar-type glitch recoveries are dominated by magnetospheric processes, in contrast to conventional radio pulsar glitch recoveries which are dominated by internal physics.

Radio pulsars are believed to have their emission powered by the loss of rotational kinetic energy. By contrast, magnetars show intense X-ray and gamma-ray radiation whose luminosity greatly exceeds that due to spin-down and is believed to be powered by intense internal magnetic fields. A basic prediction of this picture is that radio pulsars of high magnetic field should show magnetar-like emission. Here we report on a magnetar-like X-ray outburst from the radio pulsar PSR J1119-6127, heralded by two short bright X-ray bursts on 2016 July 27 and 28 (Kennea et al. 2016; Younes et al. 2016). Using Target-of-Opportunity data from the Swift X-ray Telescope and NuSTAR, we show that this pulsar's flux has brightened by a factor of > 160 in the 0.5-10 keV band, and its previously soft X-ray spectrum has undergone a strong hardening, with strong pulsations appearing for the first time above 2.5 keV, with phase-averaged emission detectable up to 25 keV. By comparing Swift-XRT and NuSTAR timing data with a pre-outburst ephemeris derived from Fermi Large Area Telescope data, we find that the source has contemporaneously undergone a large spin-up glitch of amplitude df/f = 5.74(8) E-6. The collection of phenomena observed thus far in this outburst strongly mirrors those in most magnetar outbursts and provides an unambiguous connection between the radio pulsar and magnetar populations.

4U 0142+61 is one of a small class of persistently bright magnetars. Here we report on a monitoring campaign of 4U 0142+61 from 2011 July 26 - 2016 June 12 using the Swift X-ray Telescope, continuing a 16 year timing campaign with the Rossi X-ray Timing Explorer. We show that 4U 0142+61 had two radiatively loud timing events, on 2011 July 29 and 2015 February 28, both with short soft gamma-ray bursts, and a long-lived flux decay associated with each case. We show that the 2015 timing event resulted in a net spin-down of the pulsar due to over-recovery of a glitch. We compare this timing event to previous such events in other high-magnetic-field pulsars, and discuss net spin-down glitches now seen in several young, high-B pulsars.

Rotation-powered pulsars and magnetars are two different observational manifestations of neutron stars: rotation powered pulsars are rapidly spinning objects that are mostly observed as pulsating radio sources, while magnetars, neutron stars with the highest known magnetic fields, often emit short-duration X-ray bursts. Here we report simultaneous observations of the high-magnetic-field radio pulsar PSR J1119-6127 at X-ray, with XMM-Newton & NuSTAR, and at radio energies with Parkes radio telescope, during a period of magnetar-like bursts. The rotationally powered radio emission shuts off coincident with the occurrence of multiple X-ray bursts, and recovers on a time scale of ~70 seconds. These observations of related radio and X-ray phenomena further solidify the connection between radio pulsars and magnetars, and suggest that the pair plasma produced in bursts can disrupt the acceleration mechanism of radio emitting particles.

We report on simultaneous NuSTAR and XMM-Newton observations of the magnetar 1E 1048.1\\(-\\)5937 obtained in July 2013, along with Rossi X-ray Timing Explorer (RXTE) data for the same source obtained from December 2002 through March 2012. The NuSTAR data provide a clear detection of this magnetar's persistent emission up to 20 keV. We detect a previously unreported small secondary peak in the average pulse profile in the 7-10 keV band, which grows to an amplitude comparable to that of the main peak in the 10--20 keV band. We show using RXTE data that this secondary peak is likely transient. We find that the pulsed fraction increases with energy from a value of \\(\\sim\\)0.55 at \\(\\sim\\)2 keV to a value of \\(\\sim\\)0.75 near 8 keV but shows evidence for decreasing at higher energies. After filtering out multiple bright X-ray bursts during the observation, we find that the phase-averaged spectrum from combined NuSTAR and XMM data is well described by an absorbed double blackbody plus power-law model, with no evidence for the spectral turn-up near \\(\\sim\\)10 keV as has been seen in some other magnetars. Our data allow us to rule out a spectral turn-up similar to those seen in magnetars 4U 0142+61 and 1E 2259+586 of \\(\\Delta\\Gamma >= 2\\), where \\(\\Delta\\Gamma\\) is the difference between the soft-band and hard-band photon indexes. The absence of a significant spectral turn-up is consistent with what has been observed from a particularly active subset of magnetars having high spin-inferred magnetic fields, and with previously reported trends suggesting the degree of spectral turn-up is correlated with spin-down rate and/or spin-inferred magnetic field strength.