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ATEL # 1667; M. Linares, V. Tudose (Amsterdam), S. Migliari (UCSD)
on 18 Aug 2008; 18:20 UT
Password Certification: Manuel Linares (firstname.lastname@example.org)
Subjects: Radio, X-ray, Binaries, Neutron Stars, Pulsars, Transients
Referred to by ATEL #: 1668
Following the recent reports of activity (ATels #1660, #1664, #1665, #1666) we observed the field of IGR J00291+5934 with the Westerbork Synthesis Radio Telescope (WSRT). The observation was made at 4.9 GHz for about ten hours (from 2008-08-15 20:30 UT to 2008-08-16 06:30 UT). No source is detected at the reported position (ATel #364). We can place a 3 sigma upper limit on the source flux density of 160 microJy.
Analysis of the quasi-simultaneous Swift-XRT observation (ATel #1664) gives an absorbed(unabsorbed) 2-10 keV flux of about 2.2(2.3)*10^-10 erg/cm2/s, which corresponds approximately to 11mCrab. This is lower than the X-ray flux measured near the previous radio detections in the 2004 outburst (ATels #355, #361, #364; Linares et al. 2007, ApJ). The Swift-XRT-pc spectrum obtained on August 15th, corrected for pile-up, can be fitted with an absorbed power law with photon index ~1.7 and column density nH~0.5*10^22 cm^-2 (similar to the value found by Galloway et al. 2005, and to the Galactic value, Dickey & Lockmann 1990).
We thank the WSRT team for a quick scheduling of the observation.