INTEGRAL observation of renewed activity from 4U 1608-522

ATel #2464; W. Ishibashi and C. Ferrigno (ISDC/University of Geneva), C. Sánchez-Fernández and E. Kuulkers (ESAC-ESA, Spain), J. Chenevez (National Space Institute, Denmark)
on 5 Mar 2010; 17:40 UT
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Credential Certification: Nami Mowlavi (Nami.Mowlavi@obs.unige.ch)

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On 3 March 2010 SuperAGILE detected an X-ray burst from the LMXB 4U 1608-522 (Atel #2461). Confirmation of the renewed activity of this transient source was reported by MAXI/GSC (Atel #2462).

4U1608-522 was in the IBIS/ISGRI and JEMX field of view during several observations between 2010-Feb-23 06:20 and 2010-March-03 01:04 UTC, when INTEGRAL was monitoring the inner Galactic Disk.

The source was detected by JEMX since March 2, with a flux of 17+/-2 mCrab in the 3-20 keV band. Before that time the source was not detectable by JEMX. We derive an upper limit of about 10 mCrab in the 3-20 keV band between Feb. 23 and March, 2. We suggest the onset of the outburst to happen at March 1. This in agreement with the results derived by MAXI/GSC (Atel #2462). No X-ray bursts were detected within the INTEGRAL observations.

The JEMX spectrum, accumulated between 2010-Mar-02 19:12 and 2010-Mar-03 0:57 UTC for a total exposure time of 8.8 ks, can be fit by using an absorbed power-law model. We fixed the absorption column density at 1.2E22 cm² and obtained a power-law photon index of 2.8+/-0.4. The estimated source flux in the 3-10 keV energy band is 3.3E-10 ergs/cm²/s.

During the whole observation time, the source was not detected by IBIS/ISGRI. We derive an upper limit (5-sigma) on the X-ray flux of 5-10 mCrab in the 20-40 keV band.

INTEGRAL is currently observing the field of GX 339-4 (March 4th-6th) and will continue monitoring of the inner Galactic Disk until the end of March. 4U 1608-522 will be visible during these observations

We acknowledge support from the ISDC operation team for this analysis.