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Swift/XRT detection of GRS 1741.9-2853 in outburst

ATEL # 2236; J. A. Kennea (PSU)
on 9 Oct 2009; 19:38 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Jamie A. Kennea (kennea@astro.psu.edu)

Subjects: X-ray, Transients

In Swift periodic monitoring of the Galactic Center, we have detected GRB 1741.9-2853 go into outburst, as reported by Chenevez et al. (ATEL #2235). The source is detected at a high significance in a 0.9ks observation on September 29th, in a 0.9ks observation on October 2nd, in a 0.7ks observation on October 5th, 2009, and in a 1.2ks observation on October 8th, 2009. The source was not detected in the in a 0.9ks observation of this region on September 23rd, 2009, or in any previous observations of this region in 2009. 

The average XRT Photon Counting mode spectrum (corrected for pile-up) during this time is well described by a power-law model with an absorption of 1.6 +/- 0.2 x 1023 cm-2, and a photon index of 3.2 +/- 0.3.

The X-ray flux of GRS 1741.9-2853 seen to rise in the Swift observations, with mean XRT measured flux (0.3-10 keV) of (2.8 +/- 0.2) x 10-11 erg/s/cm2, (1.8 +/- 0.1) x 10-10 erg/s/cm2, (2.8 +/- 0.1) x 10^-10 erg/s/cm2 and (1.4 +/- 0.1) x 10-9 erg/s/cm2 respectively, for the 4 observations taken so far. We note that in the most recent observation, the source is suffering from considerable pile-up due to high flux, so the error on the final flux point may be underestimated.

Monitoring of the Galactic Center region, including this source, is on-going, although we note that the region will become unobservable by Swift on November 3rd, 2009 when it will be too close to the Sun to observe. 

Analysis for this ATEL was performed utilizing the tools described in Evans et al. 2009, (MNRAS, submitted. arXiv:0812.3662).


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