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Swift J174540.2-290005.3: Detection of a faint transient near Sgr A*

ATEL # 920; J. A. Kennea (PSU), R. Wijnands (University of Amsterdam), D. N. Burrows (PSU), J. Nousek (PSU) and N. Gehrels (NASA/GSFC)
on 23 Oct 2006; 21:00 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Jamie A. Kennea (

Subjects: X-ray, Transients
Referred to by ATEL #: 921

Swift/XRT monitoring of the Galactic Center region has detected a faint transient source, Swift J174540.2-290005.3, close to Sgr A*. The source is detected in observations starting on Oct 20th, 2006, and is observed to peak at a flux of 5x10-12 erg/s/cm2 (0.5-10 keV) on Oct 22nd, 2006. Observations of archival data have shown no XRT detection of this source prior to Oct 20th. The source has the following coordinates:

RA(J2000) = 17h 45m 40.2s,
Dec(J2000) = -29m 00m 05.3s,

with an estimated error radius of 5.4 arcseconds (90% containment). This position is 23 arcseconds from Sgr A*, and is 2.2 arcseconds from the Chandra detected transient source CXOGC J174540.0-290005 (Muno et al., 2005). Assuming a distance of 8.5 kpc to the source, this would place the transient approximately 340pc from Sgr A*.

The spectrum of this source can be well fit by a absorbed power-law model with the following parameters:

N_H = (7.6 +4.8/-5.7) x 1022 cm2
Photon Index = 1.5 +/- 1.0
Reduced Chi2 = 0.91 (22 dof)

There is no detectable emission below 2 keV. Assuming 8.5 kpc distance the approximate flux, corrected for absorption, is 2x1034 erg/s (0.5-10 keV). Observations of this source with the Swift/XRT are on-going.

Reference: Muno et al. 2005 ApJ, 622, L113

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