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Swift/BAT detects increased hard X-ray activity from GX 304-1

ATEL # 2538; H. A. Krimm (CRESST/GSFC/USRA), 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 6 Apr 2010; 22:07 UT
Password Certification: Hans A. Krimm (

Subjects: X-ray, Binaries, Neutron Stars, Pulsars, Transients

The Swift/BAT hard X-ray transient monitor reports increased activity in the 15-50 keV band for the transient pulsar and Be/X-ray binary and HMXB GX 304-1. Starting on 21-Mar-2010 (MJD 55276), the source has increased in intensity from an undetectable level (one-sigma upper limit of 0.002 cts/cm2/sec or 8 mcrab) up to a current level of 0.036 0.002 cts/cm2/sec (160 mcrab) on 05-Apr-2010. This is the highest rate seen in the BAT monitor since the peak two days of its outburst in Nov-2009 (Yamamoto et al, ATel #2297) and the longest sustained outburst seen from this source since the start of the Swift mission in Nov-2004.

Examination of the light curve on the RXTE All-Sky Monitor web page shows that this recent outburst is also observed at lower X-ray energies.

Swift/BAT Hard X-ray Transient light curve for GX 304-1

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R. E. Rutledge , Editor
ATEL Mirror v1.0 Updates