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تسجيل مستخدم جديدX-ray and Near-IR Variability of the Anomalous X-ray Pulsar 1E 1048.1-5937: From Quiescence Back to Activity
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Cindy R. Tam
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(Abridged) We report on new and archival X-ray and near-infrared observations of the anomalous X-ray pulsar 1E 1048.1-5937 performed between 2001-2007 with RXTE, CXO, Swift, HST, and VLT. During its ~2001-2004 active period, 1E 1048.-5937 exhibited two large, long-term X-ray pulsed-flux flares as well as short bursts, and large (>10x) torque changes. Monitoring with RXTE revealed that the source entered a phase of timing stability in 2004; at the same time, a series of four simultaneous observations with CXO and HST in 2006 showed that its X-ray flux and spectrum and near-IR flux, all variable prior to 2005, stabilized. The near-IR flux, when detected by HST (H~22.7 mag) and VLT (K_S~21.0 mag), was considerably fainter than previously measured. Recently, in 2007 March, this newfound quiescence was interrupted by a sudden flux enhancement, X-ray spectral changes and a pulse morphology change, simultaneous with a large spin-up glitch and near-IR enhancement. Our RXTE observations revealed a sudden pulsed flux increase by a factor of ~3 in the 2-10 keV band. In observations with CXO and Swift, we found that the total X-ray flux increased much more than the pulsed flux, reaching a peak value of >7 times the quiescent value (2-10 keV). With these recent data, we find a strong anti-correlation between X-ray flux and pulsed fraction, and a correlation between X-ray spectral hardness and flux. Simultaneously with the radiative and timing changes, we observed a significant X-ray pulse morphology change such that the profile went from nearly sinusoidal to having multiple peaks. We compare these remarkable events with other AXP outbursts and discuss implications in the context of the magnetar model and other models of AXP emission.
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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 archi
val 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 present the results of X-ray and near-IR observations of the anomalous X-ray pulsar 1E 1048.1-5937, believed to be a magnetar. This AXP underwent a period of extreme variability during 2001-2004, but subsequently entered an extended and unexpected
quiescence in 2004-2006, during which we monitored it with RXTE, CXO, and HST. Its timing properties were stable for >3 years throughout the quiescent period. 1E 1048.1-5937 again went into outburst in March 2007, which saw a factor of >7 total X-ray flux increase which was anti-correlated with a pulsed fraction decrease, and correlated with spectral hardening, among other effects. The near-IR counterpart also brightened following the 2007 event. We discuss our findings in the context of the magnetar and other models.
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.
After three years of no unusual activity, Anomalous X-ray Pulsar 1E 1048.1-5937 reactivated in 2007 March. We report on the detection of a large glitch (Delta(nu)/nu =1.63(2)X~10^{-5}) on 2007 March 26 (MJD 54185.9), contemporaneous with the onset of
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