TITLE: GCN CIRCULAR NUMBER: 7946 SUBJECT: Refined analysis of Swift Trigger 316063, is IGR J08408-4503 DATE: 08/07/06 17:06:13 GMT FROM: Scott Barthelmy at NASA/GSFC D. Palmer (LANL), S.D. Barthelmy (GSFC), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), T. Sakamoto (GSFC/UMBC), P.A. Ward (MSSL-UCL), P.A. Evans, K.L. Page, A.P. Beardmore (U. Leicester) (i.e. for the Swift-BAT/-XRT teams): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT trigger #316063 (Ward, et al., GCN Circ. 7945). The BAT ground-calculated position is RA, Dec = 130.225, -45.054 deg, which is RA(J2000) = 08h 40m 54.0s Dec(J2000) = -45d 03' 13.1" with an uncertainty of 4.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted light curve shows a weak, broad, smooth peak starting at ~T-100 sec and ending at ~T+270 sec. T90 (15-350 keV) is 260 +- 80 sec (estimated error including systematics). The time-averaged spectrum from T-31.0 to T+257.0 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -0.45 +- 2.11, and Epeak of 25.6 +- 4.7 keV (chi squared 54.0 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 7.1 +- 1.2 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+88.50 sec in the 15-150 keV band is 0.07 +- 0.03 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.52 +- 0.27 (chi squared 63.8 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/316063/BA/ We have analysed 7 orbits of XRT data, comprising 133 s of Windowed Timing (WT) mode data and 14.5 ks of Photon Counting (PC) mode data. Using 7871 s of XRT Photon Counting mode data and 8 UVOT images, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching to the USNO-B1 catalogue): RA, Dec = 130.19882, -45.05864 which is equivalent to: RA (J2000): 08 40 47.72 Dec (J2000): -45 03 31.1 with an uncertainty of 1.5 arcsec (90% confidence). This location is 3 arcsec from IGR J08408-4503, within the previously reported error circle (Kennea & Campana, ATEL #818). The light curve initially shows a power-law decay, with a slope of 3.37 (+0.18/-0.14), which then breaks to an almost flat phase with alpha=0.37 (+/-0.15). Thereafter, the flux drops briefly, and then begins to rise again. The light curve can be seen online at http://www.swift.ac.uk/xrt_curves/00316063/. The spectrum is heavily absorbed; the WT mode spectrum can be modelled with a power-law of photon index 2.09 (+0.49/-0.18), an absorber fixed at the Galactic column density (9.3 x 10^21 cm^-2, Kalberla et al. 2005), and a partial covering absorber, with a column of 10.23 (+1.1/-1.5) x 10^22 cm^-2 and a covering fraction of 97%. All of the above lead us to conclude that the object observed is IGR J08408-4503 (a SFXT source), and not a GRB. This circular is an official product of the Swift team.