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XMM-Newton ToO observation of the outburst decay of the AXP 1E1048.1-5937

ATEL # 1121; Nanda Rea (SRON), Andrea Tiengo, GianLuca Israel, Sergio Campana (INAF)
on 28 Jun 2007; 10:18 UT
Password Certification: Nanda Rea (N.Rea@sron.nl)

Subjects: X-ray, Request for Observations, Neutron Stars, Pulsars

On the 22nd of March 2007 the anomalous X-ray pulsar (AXP) 1E1048.1-5937 showed a glitch (ATEL #1041) and an increase of its X-ray flux observed by RXTE (ATEL #1041), Swift (ATEL #1043; #1077) and Chandra (ATEL #1076). Following this event the source was detected in the near-IR and optical band at a high flux level (ATEL #1044; #1077; #1071).

XMM-Newton observed 1E1048.1-5937 for 48ks starting on June 14th 2007. Preliminary results show that the source flux is still enhanced in the soft X-ray range with respect to pre-glitch observations (Mereghetti et al. 2004; Tiengo et al. 2005). The source EPIC-PN spectrum is well fitted (in the 1-10keV energy range; 2% systematics added; reduced chi^2 = 1.1 (184dof)) by an absorbed blackbody plus a power-law with Nh = 1.1(1)x10^22 cm^-2, kT = 0.74(1) keV and photon index Gamma=3.2(1) (all errors are given at 90% confidence level). The unabsorbed 2-10keV flux is 2.7(1)x10^-11 erg/s/cm^2, which is decreasing with respect to the latest Swift and Chandra post-glitch observations carried out on April/May. However, the AXP is still a factor of ~5 brighter than its quiescent level.

We measure a spin period of 6.45826(1) s, with a fundamental component pulsed fraction of ~46%, highly energy dependent (from 35% to 52% from lower to higher energies; pulsed fraction defined as the background-corrected semi-amplitude of the best fitting sine component). Note that following the glitch, the nominal sinusoidal pulse profile of this source changed drastically in a multipeak profile (ATEL #1043; #1076; #1077): in this XMM-Newton observation the profile is still structured.

Monitoring observations at other wavelengths are strongly encouraged in order to follow the decaying phases of the outburst of 1E1048.1-5937.

We thank Norber Schartel and the XMM-Newton team for carrying out this ToO observation.


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