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Chandra Monitoring Observations of 1E 1048.1-5937: A Prolonged Flux Enhancement

ATEL # 1076; F. P. Gavriil (NPP Fellow/GSFC), V. M. Kaspi (McGill), P. M. Woods (Dynetics), R. Dib (McGill)
on 16 May 2007; 18:43 UT
Password Certification: Fotis Gavriil (

Subjects: X-ray, Neutron Stars, Soft Gamma-ray Repeaters
Referred to by ATEL #: 1077

In 2007 March Dib et al. 2007 reported a pulsed flux enhancement and glitch from the Anomalous X-ray pulsar (AXP) 1E 1048.1-5937 (see ATEL #1041, ATEL #1043). We initiated four Chandra ToOs to monitor the source, with the most recent being on 2007 April 28. Post-glitch, the source continues to be bright with an unabsorbed 2-10 keV flux of ~3.6x10^-11 erg cm^2 s^-1 in all Chandra observations. Note that the quiescent flux of this source is ~4.7x10^-12 erg cm^2 s^-1. We find that the pulsed fraction and the total flux are anti-correlated, as was noted by Tiengo et al. 2005 (ApJ, 437:997) and Gavriil et al. (2006, ApJ, 641:418). Furthermore, we find from our Chandra analysis that the pulse profile has shown significant morphology changes. The profile is nominally a sinusoid but has become, and remained, multi-peaked following the flux enhancement. Observations at other wavelengths remain strongly encouraged.

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