No Arabic abstract
We have carried out a search for the optical and infrared counterpart of the Anomalous X-ray Pulsar 1E 1841-045, which is located at the center of the supernova remnant Kes73. We present the first deep optical and infrared images of the field of 1E 1841-045, as well as optical spectroscopy results that exclude the brightest objects in the error circle as possible counterparts. A few of the more reddened objects in this region can be considered as particularly interesting candidates, in consideration of the distance and absorption expected from the association with Kes73. The strong interstellar absorption in the direction of the source does not allow to completely exclude the presence of main sequence massive companions.
We report the discovery of non-thermal pulsed X-ray/soft gamma-ray emission up to about 150 keV from the anomalous X-ray pulsar AXP 1E 1841-045 located near the centre of supernova remnant Kes 73 using RXTE PCA and HEXTE data. The morphology of the double-peaked pulse profile changes rapidly with energy from 2 keV up to about 8 keV, above which the pulse shape remains more or less stable. The pulsed spectrum is very hard, its shape above 10 keV can be described well by a power law with a photon index of 0.94 +/- 0.16. 1E 1841-045 is the first AXP for which such very-hard pulsed emission has been detected, which points to an origin in the magnetosphere of a magnetar.
We present Keck R and I band images of the field of the anomalous X-ray pulsar 1E 2259+58.6. We derive an improved X-ray position from archival ROSAT HRI observations by correcting for systematic (boresight) errors. Within the corresponding error circle, no object is found on the Keck images, down to limiting magnitudes R = 25.7 and I = 24.3. We discuss the constraints imposed by these limits, and conclude that it is unlikely that 1E 2259+58.6 is powered by accretion from a disk, irrespective of whether it is in a binary or not, unless the binary is extremely compact.
Swift/BAT detected the first burst from 1E 1841-045 in May 2010 with intermittent burst activity recorded through at least July 2011. Here we present Swift and Fermi/GBM observations of this burst activity and search for correlated changes to the persistent X-ray emission of the source. The T90 durations of the bursts range between 18-140 ms, comparable to other magnetar burst durations, while the energy released in each burst ranges between (0.8 - 25)E38 erg, which is in the low side of SGR bursts. We find that the bursting activity did not have a significant effect on the persistent flux level of the source. We argue that the mechanism leading to this sporadic burst activity in 1E 1841-045 might not involve large scale restructuring (either crustal or magnetospheric) as seen in other magnetar sources.
We report our discovery of the likely near-infrared counterpart to the anomalous X-ray pulsar (AXP) 1E1048.1-5937, using observations from the 6.5-m Baade (Magellan-I) telescope in Chile. We derived a precise position for the X-ray source using archival data from the Chandra X-Ray Observatory. This position is inconsistent with a position reported earlier from XMM-Newton, but we show that the originally reported XMM-Newton position suffered from attitude reconstruction problems. Only two of the infrared objects in a 17 arcsec x 17 arcsec field containing the target have unusual colors, and one of these has colors consistent with those of the identified counterparts of two other AXPs. The latter object is also the only source detected within the 0.6 arcsec Chandra error circle, and we identify it as the counterpart to 1E1048.1-5937. This is the first AXP counterpart detected in multiple infrared bands, with magnitudes J=21.7(3), H=20.8(3), and K=19.4(3). There is marginal evidence for spectral flattening at longer wavelengths.
We report on optical and infrared observations of the anomalous X-ray pulsar (AXP) 1E 1048.1-5937, made during its ongoing X-ray flare which started in 2007 March. We detected the source in the optical I and near-infrared Ks bands in two ground-based observations and obtained deep flux upper limits from four observations, including one with the Spitzer Space Telescope at 4.5 and 8.0 microns. The detections indicate that the source was approximately 1.3--1.6 magnitudes brighter than in 2003--2006, when it was at the tail of a previous similar X-ray flare. Similar related flux variations have been seen in two other AXPs during their X-ray outbursts, suggesting common behavior for large X-ray flux variation events in AXPs. The Spitzer flux 1E 1048.1-5937 limits are sufficiently deep that we can exclude mid-infrared emission similar to that from the AXP 4U 0142+61, which has been interpreted as arising from a dust disk around the AXP. The optical/near-infrared emission from probably has a magnetospheric origin. The similarity in the flux spectra of 4U 0142+61 and 1E 1048.1-5937 challenges the dust disk model proposed for the latter.