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Swift and RXTE report the detection of a new galactic transient source Swift J1713.4-4219

ATEL # 2300; H. A. Krimm (CRESST/GSFC/USRA), T. E. Strohmayer (GSFC), J. H. Swank (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 17 Nov 2009; 4:38 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Hans A. Krimm (

Subjects: X-ray, Request for Observations, Binaries, Black Holes, Variables

The hard X-ray transient monitor of the Swift Burst Alert Telescope (BAT) has detected a previously unknown transient source. This source, Swift J1713.4-4219, was first detected at a daily average rate of 0.0048 0.0017 counts/sec/cm2 (21 mCrab) in the 15-50 keV band on 2009 Nov 13 (MJD 55148). It was visible at a lower significance for four days prior and has remained at roughly the same brightness for the past three days.

Observing constraints prevent an observation with the Swift X-Ray Telescope (XRT) until 2010 Jan 23. The BAT position was determined to be:

RA (J2000): 17 13 26.6 (258.361 deg)
DEC (J2000): -42 19 37.2 (-42.327 deg)
The estimated error is 3.0 arc minutes (radius, 90% confidence).

The position of the new hard X-ray transient Swift J1713.4-4219 was observed with RXTE for 1.5 ksec beginning on 2009 Nov 16 at 19:41:38 UTC. The source is detected in the PCA with an average rate of 17.0 +- 0.2 counts/s/PCU (full PCA band). Strong flickering is evident in the light curve, with peak rates approaching 70 counts/s/PCU. Timing analysis reveals no significant periodicities, but the strong, aperiodic variability is easily detected in the power spectrum. The PCA spectrum is well fitted (2.5-30 keV) with a column density of 1.2+-0.4 x 10^22 cm2 and power-law index of 1.68 +- 0.04. The average flux is approximately 5.4 mCrab. The present data are consistent with a black hole transient in the low-hard state. Additional RXTE observations are planned over the next few days before the source is too close to the Sun for RXTE to observe.

Swift/BAT Hard X-ray Transient light curve for Swift J1713.4-4219

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