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Register a new userThe Long-term Radiative Evolution of Anomalous X-ray Pulsar 1E 2259+586 after its 2002 Outburst
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We present an analysis of five X-ray Multi-Mirror Mission (XMM) observations of the anomalous X-ray pulsar (AXP) 1E 2259+586 taken in 2004 and 2005 during its relaxation following its 2002 outburst. We compare these data with those of five previous XMM observations taken in 2002 and 2003, and find the observed flux decay is well described by a power-law of index -0.69+/-0.03. As of mid-2005, the source may still have been brighter than preoutburst, and was certainly hotter. We find a strong correlation between hardness and flux, as seen in other AXP outbursts. We discuss the implications of these results for the magnetar model.
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We present the results of a near-infrared monitoring program of the Anomalous X-ray Pulsar 1E 2259+586, performed at the Gemini Observatory. This program began three days after the pulsars 2002 June outburst, and spans ~1.5 years. We find that after an initial increase associated with the outburst, the near-infrared flux decreased continually and reached the pre-burst quiescent level after about one year. We compare both the near-infrared flux enhancement and its decay to those of the X-ray afterglow, and find them to be remarkably consistent. Fitting simple power laws to the RXTE pulsed flux and near-infrared data for t>1 day post-burst, we find the following decay indices: alpha=-0.21+/-0.01 (X-ray), alpha=-0.21+/-0.02 (near-infrared), where flux is a function of time such that F is proportional to t^alpha. This suggests that the enhanced infrared and X-ray fluxes have a physical link post-outburst, most likely from the neutron-star magnetosphere.
(abridged) An outburst of more than 80 individual bursts, similar to those seen from Soft Gamma Repeaters (SGRs), was detected from the Anomalous X-ray Pulsar (AXP) 1E 2259+586 in 2002 June. Coincident with this burst activity were gross changes in the pulsed flux, persistent flux, energy spectrum, pulse profile and spin down of the underlying X-ray source. We present RXTE and XMM-Newton observations of 1E 2259+586 that show the evolution of the aforementioned source parameters during and following this episode. Specifically, we observe an X-ray flux increase by more than an order of magnitude having two distinct components. The first component is linked to the burst activity and decays within ~2 days during which the energy spectrum is considerably harder than during the quiescent state of the source. The second component decays over the year following the glitch according to a power law in time with an exponent -0.22 +/- 0.01. The pulsed fraction decreased initially to ~15% RMS, and the pulse profile changed significantly during the outburst. A glitch was observed in 1E 2259+586 that preceded the observed burst activity. A fraction of the glitch (~19%) recovered, although the recovery was not purely exponential. An exponential rise of ~20% of the frequency jump with a time scale of ~14 days results in a significantly better fit to the data, however, contamination from a systematic drift in the phase of the pulse profile cannot be excluded. The long-term post-glitch spin-down rate decreased in magnitude relative to the pre-glitch value. A comparison with SGR outburst properties, a physical interpretation of the results, and implications on the number of magnetar candidates in our Galaxy are discussed.
Magnetic field geometry is expected to play a fundamental role in magnetar activity. The discovery of a phase-variable absorption feature in the X-ray spectrum of SGR 0418+5729, interpreted as cyclotron resonant scattering, suggests the presence of very strong non-dipolar components in the magnetic fields of magnetars. We performed a deep XMM-Newton observation of pulsar 1E 2259+586, to search for spectral features due to intense local magnetic fields. In the phase-averaged X-ray spectrum, we found evidence for a broad absorption feature at very low energy (0.7 keV). If the feature is intrinsic to the source, it might be due to resonant scattering/absorption by protons close to star surface. The line energy implies a magnetic field of ~ 10^14 G, roughly similar to the spin-down measure, ~ 6x10^13 G. Examination of the X-ray phase-energy diagram shows evidence for a further absorption feature, the energy of which strongly depends on the rotational phase (E >~ 1 keV ). Unlike similar features detected in other magnetar sources, notably SGR 0418+5729, it is too shallow and limited to a small phase interval to be modeled with a narrow phase-variable cyclotron absorption line. A detailed phase-resolved spectral analysis reveals significant phase-dependent variability in the continuum, especially above 2 keV. We conclude that all the variability with phase in 1E 2259+586 can be attributed to changes in the continuum properties which appear consistent with the predictions of the Resonant Compton Scattering model.
We present X-ray imaging, timing, and phase resolved spectroscopy of the anomalous X-ray pulsar 1E 2259+58.6 using the Chandra X-ray Observatory. The spectrum is well described by a power law plus blackbody model with power law index = 3.6(1), kT_BB = 0.412(6) keV, and N_H=0.93(3) x 10^{22} cm^{-2}; we find no evidence for spectral features (0.5-7.0 keV). We derive a new, precise X-ray position for the source and determine its spin period, P=6.978977(24) s. Time resolved X-ray spectra show no significant variation as a function of pulse phase. We have detected excess emission beyond 4 arcsec from the central source extending to beyond 100 arcsec, due to the supernova remnant and possibly dust scattering from the interstellar medium.
We report on new broad band spectral and temporal observations of the magnetar 1E 2259+586, which is located in the supernova remnant CTB 109. Our data were obtained simultaneously with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift, and cover the energy range from 0.5-79 keV. We present pulse profiles in various energy bands and compare them to previous RXTE results. The NuSTAR data show pulsations above 20 keV for the first time and we report evidence that one of the pulses in the double-peaked pulse profile shifts position with energy. The pulsed fraction of the magnetar is shown to increase strongly with energy. Our spectral analysis reveals that the soft X-ray spectrum is well characterized by an absorbed double-blackbody or blackbody plus power-law model in agreement with previous reports. Our new hard X-ray data, however, suggests that an additional component, such as a power-law, is needed to describe the NuSTAR and Swift spectrum. We also fit the data with the recently developed coronal outflow model by Beloborodov for hard X-ray emission from magnetars. The outflow from a ring on the magnetar surface is statistically preferred over outflow from a polar cap.
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