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ATEL # 3051; H. A. Krimm (CRESST/GSFC/USRA), R. H. D. Corbett (UMBC/NASA GSFC), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), D. Palmer (LANL), T. Sakamoto (CRESTT/GSFC/UMBC), G. Skinner (CRESST/GSFC/UMD), M. Stamatikos (OSU/GSFC), J. Tueller (GSFC), T. Ukwatta (GSFC/GWU)
on 23 Nov 2010; 0:27 UT
Password Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)
Subjects: X-ray, Binaries, Black Holes, Neutron Stars, Transients
The Swift/BAT hard X-ray transient monitor reports renewed activity in the 15-50 keV band for the highly-absorbed high mass X-ray binary system IGR J16318-4848. The source has increased in intensity from its normal average level of 0.005 cts/cm2/s (~20 mCrab) up to 0.014 ± 0.002 cts/cm2/sec (60 mcrab) on 2010-Nov-13 (MJD 55513) rising to 0.027 ± 0.003 cts/cm2/sec (120 mcrab) on 2010-Nov-20. The daily average light curve over this period shows some variability at the 2-3 sigma level. The first two Swift pointings at the source position on 2010-Nov-22 suggest that the flux has started to decline.
This is the third large outburst (>130 mCrab and 10.0 sigma) of IGR J16318-4848 seen since the launch of Swift in 2004. The earlier outbursts were in January 2006 (peak rate on MJD 53757 of ~280 mCrab) and September 2008 (peak rate on MJD 54719 of ~230 mCrab). The earlier outbursts each lasted approximately 20 days. We note that the time intervals between the first two large outbursts is an integral multiple (12) of the 80.2-day orbital period for IGR J16318-4848 proposed by Jain, Paul and Dutta (2009, Research in Astronomy and Astrophysics 9, 1303). Although we do not yet know the peak of the current outburst, the time interval between the second large outburst and MJD 55521 is ten times the proposed orbital period and hence consistent with an 80.2-day period.
Swift/BAT Hard X-ray Transient light curve for IGR J16318-4848