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INTEGRAL observes continued activity from AXP 1E1547.0-5408

ATel #1908; C. Baldovin, V. Savchenko, V. Beckmann, A. Neronov (ISDC), D. Goetz (CEA/Saclay), P. den Hartog, W. Hermsen, L. Kuiper (SRON), S. Mereghetti (IASF/INAF Milano), K. Hurley (UCB)
on 25 Jan 2009; 18:24 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Volker Beckmann (Volker.Beckmann@obs.unige.ch)

Subjects: X-ray, Gamma Ray, Neutron Star, Soft Gamma-ray Repeater, Transient

Referred to by ATel #: 1921, 1922

INTEGRAL performed a ToO observation on the AXP 1E1547.0-5408, triggered by the intense outbursts detected on 2009-01-22 (GCN 8837, 8834, 8833). The still ongoing INTEGRAL observation started at 2009-01-24T15:31 and will last for 100 ks. Within the first 80 ks of the observation, the AXP is detected by IBIS/ISGRI with 14.6 sigma significance and a flux of 9.8±0.7 mCrab (20-40 keV). The 20-150 keV spectrum can be fit by a simple power law model with photon index 1.8±0.2 and a model flux of f(20-150 keV) = 2.6e-10 erg/cm**2/sec.

During the observation, more than 15 short bursts were detected in IBIS/ISGRI, with durations ranging from 10 ms to about 1 second. A preliminary, non-exhaustive list of burst times and durations is as follows:

burst start time [UT]     duration [ms]  
2009-01-24T15:48:34        50   
           22:29:45       110   
           23:41:30      50+50 (double peaked at 1s interval)  
2009-01-25T03:07:25        10  
           03:37:00        30  
           04:17:19       110  
           05:22:09       500 (plus a 200 ms precursor 4s before)  
           05:25:05       600 (3 peaks of 200 ms each)  
           05:35:17       150  
           06:39:01       800  
           08:43:43     >1000 
The last event of this list was saturated in IBIS/ISGRI. This burst is also detected by INTEGRAL SPI-ACS and by Konus-Wind (GCN 8851).

A 2.5 ksec Swift/XRT observation, which started at 2009-01-24T06:16, can also be fit by a simple absorbed power law model in the 0.3-8 keV range (photon index 2.8±0.1, hydrogen column density 4.3±0.3 e22 1/cm**2), but shows a flux level about 8 times lower than the later IBIS/ISGRI data, indicating strong variability. The XRT image still shows the dust halos reported by Tiengo et al. 2009 (GCN 8848).

The SPI-ACS events can be found under http://isdc.unige.ch/Soft/ibas/ibas_acs_web.cgi

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