//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21960 SUBJECT: GRB 171003A: Swift detection of a burst or a Galactic Transient DATE: 17/10/03 03:22:38 GMT FROM: Scott Barthelmy at NASA/GSFC S. B. Cenko (GSFC), S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Swift Team: At 02:37:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 171003A (trigger=775946). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 40.910, +61.408, which is RA(J2000) = 02h 43m 38s Dec(J2000) = +61d 24' 28" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for image triggers, the real-time light curve does not show anything significant. The XRT began observing the field at 02:43:29.0 UT, 388.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 40.9186, 61.4323 which is equivalent to: RA(J2000) = +02h 43m 40.46s Dec(J2000) = +61d 25' 56.3" with an uncertainty of 5.4 arcseconds (radius, 90% containment). This location is 88 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 1.29e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 400 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain extinction expected. The analysis is complicated by the proximity of a known star with a USNO V magnitude of 12.01 approximately 7.7 arc-seconds from the XRT position. Based on this source's proximity to the Galactic plane (latitude=1.4 degrees) and the duration of the BAT image trigger (>5 minutes), there is a possibility that this is a Galactic transient (i.e. Swift J0243.6+6124) rather than a GRB. The nature of this source will be determined by the full downloaded dataset and further observations. Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21961 SUBJECT: GRB 171003A: LT early optical observations DATE: 17/10/03 10:34:35 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), T. Laskar (UC Berkeley) on behalf of a large collaboration report: The Liverpool Telescope automatically began observing Swift possible GRB 171003A (Cenko et al. GCN 21960) on October 03, 02:51:26 UT (14 minutes after the GRB trigger time) with RINGO3 polarimeter and IO:O camera in the SDSS R filter. In addition to the presence of a couple of catalogued bright objects, within the Swift-XRT error circle we very marginally detect a possible faint, uncatalogued object at the following position: RA(J2000) =  02:43:40.65 DEC(J2000)= +61:25:53.6 at ~9" from the bright stars above mentioned, with an error radius of about 1" and a magnitude of r'=21.3 +- 0.3 (in a 6x10s frame at 48 minutes post GRB), as calibrated against Pan-STARRS field stars. The same possible source is not detected by us earlier, at a mid time of 19 minutes post GRB down to r'>20.5 mag. Combining the two measures, a corresponding upper limit of alpha<0.8 is obtained on the average power-law decay index. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21963 SUBJECT: Swift Trigger 775946 is a Galactic transient, not GRB 171003 DATE: 17/10/03 11:44:51 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J.A. Kennea (PSU) and S.B. Cenko (NASA/GSFC) report on behalf of the Swift Team: BAT trigger 775946 (GCN #21960) is confirmed to be a Galactic Transient, Swift J0243.6+6124. Swift/XRT observations show the source to continue to be bright with evidence of brightening over three orbits of observations. We note also a reported possible detection of brightening of LSI +61 303 by MAXI (ATEL #10803) is likely due to this new transient (LSI +61 303 is 25 arc-minutes away from the XRT position reported in GCN #21960). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21965 SUBJECT: GRB 171003A: Enhanced Swift-XRT position DATE: 17/10/03 14:29:33 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 1963 s of XRT Photon Counting mode data and 2 UVOT images for GRB 171003A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 40.91793, +61.43411 which is equivalent to: RA (J2000): 02h 43m 40.30s Dec (J2000): +61d 26' 02.8" with an uncertainty of 1.5 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team.