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Possible pulsation period in SGR 1833-0832

ATEL # 2494; Paolo Esposito, Gian Luca Israel, Luigi Stella, Nanda Rea, Andrea Tiengo
on 20 Mar 2010; 17:12 UT
Password Certification: Paolo Esposito (paoloesp@iasf-milano.inaf.it)

Subjects: X-ray, Soft Gamma-ray Repeaters
Referred to by ATEL #: 2515, 2550

We analysed 22.5 ks of XRT data in Photon Counting (PC) mode of the new soft gamma-ray repeater candidate SGR 1833-0832 (Gelbord et al. GCN Circ. 10526, 10531). The data were barycentered using the X-ray position reported in Evans et al. (GCN Circ. 10530). We detect strong pulsations from the X-ray source in the 2-10 keV band at 7.5653(5) sec. The background subtracted pulsed fraction, defined as the semiamplitude of sinusoidal modulation divided by the mean source count rate, is 64+/-4%. The pulse is highly significant (the probability of such a signal to appear by chance in the search, taking into account the 32768 trials, is about 5E-18) and is not present in the background data. We caution however that this value is close to three times the XRT PC frame time, 2.507 s. At the link below a plot of the source and background data folded at our best fit period and at 3*2.507 s can be seen. Further observations are needed to confirm this period. http://www.iasf-milano.inaf.it/~paoloesp/sgr1833.html


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