INTEGRAL hard X-ray observations of the outburst of the AXP CXOU J164710.2-455216

ATel #953; D. Gotz (CEA-Saclay), G. L. Israel (INAF-OAR), S. Mereghetti (INAF-IASF Milano), S. Balman (ESA/ESTEC), T. Belloni (INAF-OAB), M. Del Santo, A. Tarana, A. Bazzano, M. Fiocchi (INAF-IASF Roma), C. Ferrigno (INAF-IASF Palermo), J.-C. Leyder (IAG Liege), A. Paizis , L. Sidoli (INAF-IASF Milano), K. Pottschmidt (UCSD), K. Watanabe (GSFC), G. Weidenspointner (CESR Toulouse)
on 29 Nov 2006; 11:07 UT
Credential Certification: Diego Gotz (diego.gotz@cea.fr)

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During the Key Project observations of the Galactic centre region performed in September and October 2006, INTEGRAL covered the position of the transient AXP CXOU J164710.2-455216. The source was inside the IBIS field of view starting from September 21 2006 at 21:07 UT, about 20 hours after the Swift detection of an intense short burst and a long outburst from this AXP (ATEL #893 and ATEL #894).

The source was located at a large off-axis angle and was observed discontinuously (due to the satellite dithering strategy) for a total of 23 ks until September 22 at 12:49. This corresponds to the brightest part of the outburst during which the 1-10 keV unabsorbed flux was about 10^-10 erg cm^-2 s^-1 (ATEL #896). Using IBIS/ISGRI data we looked for soft gamma-ray emission at the AXP position. We do not detect the source and we inferred a 3 sigma upper limit of 5x10^-11 erg cm^-2 s^-1 in the 20-40 keV band, and of 1.7x10^-10 erg cm^-2 s^-1 in the 40-200 keV band (assuming a Crab-like spectrum). Given that the ratio of the X-ray/soft gamma-ray flux measured in persistent AXPs is of the order of 0.1-1 (Kuiper et al. 2006, ApJ, 645, 556; Götz et al., 2006, A&A, 449, L31), our upper limits indicate a rather soft spectrum for this AXP during its outburst.

By extending our search until October 1st at 19:17 UT, our exposure increases to 42 ks, and the derived upper limits are 3.6x10^-11 erg cm^-2 s^-1 and 1.1x-10^-10 erg cm^-2 s^-1, respectively in the same energy bands as above.