//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21097 SUBJECT: GRB 170516A: Swift detection of a burst DATE: 17/05/16 13:06:41 GMT FROM: Scott Barthelmy at NASA/GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), P.A. Evans (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 12:49:20 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170516A (trigger=753110). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 41.598, -55.899, which is RA(J2000) = 02h 46m 24s Dec(J2000) = -55d 53' 54" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a couple peaks with a total duration of about 35 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~3 sec after the trigger. The XRT began observing the field at 12:50:41.1 UT, 80.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 41.5663, -55.9092 which is equivalent to: RA(J2000) = +02h 46m 15.91s Dec(J2000) = -55d 54' 33.1" with an uncertainty of 6.4 arcseconds (radius, 90% containment). This location is 73 arcseconds from the BAT onboard position, within the BAT error circle. The initial flux in the 2.5 s image was 4.96e-10 erg cm^-2 s^-1 (0.2-10 keV). Automated UVOT data processing is currently not working, but manual inspection of the UVOT image shows no GRB afterglow counterpart. Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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: 21098 SUBJECT: GRB 170516A: Enhanced Swift-XRT position DATE: 17/05/16 19:11:18 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2335 s of XRT Photon Counting mode data and 6 UVOT images for GRB 170516A, 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 = 41.56858, -55.90968 which is equivalent to: RA (J2000): 02h 46m 16.46s Dec (J2000): -55d 54' 34.8" with an uncertainty of 1.8 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21099 SUBJECT: GRB 170516A: Swift/UVOT Upper Limits DATE: 17/05/16 22:02:21 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170516A 87 s after the BAT trigger (Lien et al., GCN Circ. 21097). No optical afterglow consistent with the XRT position (Lien et al. GCN Circ. 21097) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 87 237 147 >20.1 white 87 5703 541 >21.1 v 4478 6113 393 >19.8 b 3863 5498 393 >20.6 u 299 5293 379 >19.4 w1 4888 5088 197 >19.4 m2 4683 6222 299 >20.5 w2 4274 5909 393 >20.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21101 SUBJECT: GRB 170516A: Swift-XRT refined Analysis DATE: 17/05/17 00:12:43 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), A. Cholden-Brown (PSU), S. J. LaPorte (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and A.Y. Lien report on behalf of the Swift-XRT team: We have analysed 7.2 ks of XRT data for GRB 170516A (Lien et al. GCN Circ. 21097), from 69 s to 34.9 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 21098). The light curve can be modelled with an initial power-law decay with an index of alpha=3.78 (+4.22, -0.29), followed by a break at T+232 s to an alpha of 0.55 (+/-0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.07 (+0.25, -0.23). The best-fitting absorption column is 9.1 (+6.2, -5.2) x 10^20 cm^-2, in excess of the Galactic value of 3.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 9.1 (+6.2, -5.2) x 10^20 cm^-2 Galactic foreground: 3.1 x 10^20 cm^-2 Excess significance: 1.9 sigma Photon index: 2.07 (+0.25, -0.23) If the light curve continues to decay with a power-law decay index of 0.55, the count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.9 x 10^-13 (6.0 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00753110. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21102 SUBJECT: GRB 170516A: Swift-BAT refined analysis DATE: 17/05/17 01:07:14 GMT FROM: Hans Krimm at NASA-GSFC/NSF J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170516A (trigger #753110) (Lien, et al., GCN Circ. 21097). The BAT ground-calculated position is RA, Dec = 41.543, -55.929 deg which is RA(J2000) = 02h 46m 10.4s Dec(J2000) = -55d 55' 44.2" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 67%. The mask-weighted light curve shows two fairly symmetrical triangular peaks. The first starts at T-5 s, peaks at T+2 s and decays by T+10 s. The second peak starts at T+10 s, has a broad peak from T+15 to T+20 and decays by T+28 s. The spacecraft slewed away from the burst position at about T+550 sec. T90 (15-350 keV) is 36.78 +- 11.61 sec (estimated error including systematics). The time-averaged spectrum from T-19.86 to T+31.22 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.13 +- 0.87, and Epeak of 19.1 +- 12.4 keV (chi squared 37.46 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 8.5 +- 0.9 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+1.27 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.67 +- 0.17 (chi squared 47.73 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/753110/BA/