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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
Password Certification: Diego Gotz (diego.gotz@cea.fr)

Subjects: X-ray, Gamma Ray, Neutron Stars, Pulsars, Transients

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.


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