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Detection of periodic X-ray modulation of SFXT IGR J16207-5129 in the Swift-BAT light curve

ATel #3785; Chetana Jain (Hans Raj College, University of Delhi), Biswajit Paul (Raman Research Institute, Bangalore), Chandreyee Maitra (Raman Research Institute, Bangalore)
on 28 Nov 2011; 16:19 UT
Credential Certification: Chetana Jain (chetanajain11@gmail.com)

Subjects: X-ray

We report detection of a periodic intensity modulation in the Supergiant Fast X-ray Transient (SFXT) IGR J16207-5129 in the long term 15-50 keV light curve obtained with the Swift Burst Alert Telescope (BAT) between MJD 53413 and 55888. Using the Lomb-Scargle periodogram technique, we have found a period of 9.726 d. This can be the orbital period of the X-ray binary. The light curve, folded with this period shows a complex shape with a large modulation factor. The maximum intensity is more than a factor of 2 compared to the average intensity and in some phases the count rate is low, equivalent to the X-ray source being in eclipse. IGR J16207-5129 belongs to the class of persistent SFXTs (Tomsick et al. 2006, ApJ, 647, 1309). A prolonged reduction in the X-ray flux detected in a Suzaku observation (Bodaghee et al. 2010, ApJ, 719,451) that was interpreted as a possible eclipse does not coincide with the phase at which the Swift-BAT light shows lowest intensity. If the periodic modulation in the Swift-BAT lightcurve is indeed the orbital period, the X-ray intensity reduction in the Suzaku light curves is likely to be an absorption event.