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The energy source of the anomalous X-ray pulsars (AXPs) is not understood, hence their designation as anomalous. Unlike binary X-ray pulsars, no companions are seen, so the energy cannot be supplied by accretion of matter from a companion star. The loss of rotational energy, which powers radio pulsars, is insufficient to power AXPs. Two models are generally(More)
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(More)
The detection of optical/infrared counterparts to Anomalous X-ray Pulsars (AXPs) has greatly increased our understanding of these systems. Models for the AXP phenomenon were based upon their X-ray emission, and all but the magnetar model made predictions for the optical/infrared that have now been falsified. With detections in hand, detailed studies of the(More)
We present high-speed, multi-colour optical photometry of the anomalous X-ray pulsar 4U 0142+61, obtained with ULTRACAM on the 4.2-m William Herschel Telescope. We detect 4U 0142+61 at magnitudes of i ′ = 23.7 ± 0.1, g ′ = 27.2 ± 0.2 and u ′ > 25.8, consistent with the magnitudes found by Hulleman et al. (2004) and hence confirming their discovery of both a(More)
We report the discovery of the X-ray transient SAX J2103.5+4545 which was active from February to Septem-ber 1997. The observed peak intensity of 20 mCrab (2 to 25 keV) occurred on April 11. An analysis of data obtained around the time of the peak revealed a pulsed signal with a period of 358.61 ± 0.03 s on MJD 50569. The pulse profile has a pulsed fraction(More)
We report the discovery of the X-ray transient SAX J2103.5+4545 which was active from Febru-ary to September 1997. The observed peak intensity of 20 mCrab (2 to 25 keV) occurred on April 11. An analysis of data obtained around the time of the peak revealed a pulsed signal with a period of 358.61 ± 0.03 s on MJD 50569. The pulse profile has a pulsed fraction(More)
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