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GCN Circular 15172

Subject
Swift trigger 569022 is a new Galactic source Swift J1734.5-3027
Date
2013-09-03T17:12:33Z (11 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), J. A. Kennea, D. N. Burrows (PSU), J. R. 
Cummings (GSFC/UMBC), C. B. Markwardt, N. Gehrels (GSFC), T. N. Ukwatta 
(MSU), B. Sbarufatti (PSU), C. J. Mountford (Leicester), H. A. Krimm 
(GSFC/USRA), M. H. Siegel, M. M. Chester, D. Grupe (PSU), report:

The Swift team has carried out further analysis of trigger 569022 
(Malesani et al., GCN 15157; Kennea et al., ATel 5354).

The BAT emission is extremely soft, and using the full data set the 
spectrum is best fit with a black body function with a temperature of 
2.57+-0.22 keV (reduced chi^2 = 0.79, where the small value is due to 
allowances for systematic errors). The best fit simple power law 
(reduced chi^2 = 0.93) has a photon index of 5.87+-0.43.

The X-ray light curve shows an initial decay with very prominent dips 
(by a factor of 10 in flux), and is observed to rise starting around 60 
ks after the trigger. The time-averaged spectrum during the first orbit 
is not well fit by an absorbed power law, but can be described with an 
absorbed black-body model with kT = 1.50+-0.02 keV and N_H = 
(0.67+-0.05)*10^22 cm^-2. UVOT detected no bright counterpart, which is 
expected given the large Galactic extinction towards this sightline.

Given the above properties, unusual among cosmic GRBs, and the position 
2.8 deg away from the Galactic centre, we conclude that the trigger is 
not due to a GRB, but is a new Galactic transient that we name Swift 
J1734.5-3027 (Kennea et al., ATel 5354).

Automatic BAT and XRT products are available at the following URLs:

http://gcn.gsfc.nasa.gov/notices_s/569022/BA/
http://www.swift.ac.uk/possible_GRBs/00569022/source1

This circular is an official product of the Swift team.
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