//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21135 SUBJECT: GRB 170524A: Swift detection of a burst (or possible new SGR) DATE: 17/05/24 20:06:28 GMT FROM: Scott Barthelmy at NASA/GSFC J.G. Gropp (PSU), S. D. Barthelmy (GSFC), C. Gronwall (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 19:49:15 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170524A (trigger=754322). Swift slewed immediately to the source. The BAT on-board calculated location is RA, Dec 319.456, +48.587, which is RA(J2000) = 21h 17m 49s Dec(J2000) = +48d 35' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 0.25 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 19:50:16.0 UT, 60.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 319.4869, 48.6065 which is equivalent to: RA(J2000) = 21h 17m 56.86s Dec(J2000) = +48d 36' 23.4" with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 101 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. UVOT took a finding chart exposure of 150 seconds with the White filter starting 67 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. We note that this is a short burst, close to the Galactic plane (lat = -0.5 degrees), although far from the Galactic center (lon = 91 degrees). Thus there is a possibility that this is a previously unknown Soft Gamma Repeater (SGR). However, the preliminary 4-energy lightcurve shows more flux above 100 keV than is typical for an SGR burst. Burst Advocate for this burst is J.G. Gropp (jdg44 AT psu.edu). 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: 21136 SUBJECT: GRB 170524A: Enhanced Swift-XRT position DATE: 17/05/25 03:30:05 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 467 s of XRT Photon Counting mode data and 1 UVOT images for GRB 170524A, 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 = 319.48641, +48.60687 which is equivalent to: RA (J2000): 21h 17m 56.74s Dec (J2000): +48d 36' 24.7" with an uncertainty of 4.3 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: 21139 SUBJECT: GRB 170524A: Swift-XRT refined Analysis DATE: 17/05/25 10:53:11 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Cholden-Brown (PSU), S.L. Gibson (U. Leicester) and J.G. Gropp report on behalf of the Swift-XRT team: We have analysed 9.9 ks of XRT data for GRB 170524A (Gropp et al. GCN Circ. 21135), from 69 s to 46.6 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 21136). There is evidence that the source may be fading, however we cannot constrain the decay at the current time The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00754322. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21140 SUBJECT: GRB 170524A: D50 optical observation and limit DATE: 17/05/25 10:57:36 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov Jan Štrobl, René Hudec and Martin Jelínek (ASÚ CAS, Ondřejov, CZ) We observed the location of the recently discovered GRB 170524A (Gropp et al., GCNC 21135) with the 0.5m robotic telescope D50 located in Ondřejov, Czech Republic. The unfiltered CCD observations started 4 hours after the trigger, once the position got available above local horizon, and had to be interrupted after 20 minutes because of passing clouds. The sum of all images obtained has a mean exposure time 00:02:23UT, i.e. 4.22h after the GRB, and a limiting magnitude of R>20.2. No object was detected within the XRT errorbox (Evans et al., GCNC 21136). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21141 SUBJECT: GRB 170524A: Swift/UVOT Upper Limits DATE: 17/05/25 12:37:02 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (UCL-MSSL) and J.G. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170524A 67 s after the BAT trigger (Gropp et al., GCN Circ. 21135). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 21136) 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 67 217 147 >20.4 u_FC 280 529 246 >19.5 white 67 1007 334 >20.6 v 610 1058 58 >17.9 b 535 1157 58 >18.7 u 280 1132 285 >19.5 w1 660 1107 58 >18.3 m2 1063 1082 19 >17.3 w2 586 1033 58 >18.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 2.82 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21143 SUBJECT: GRB 170524A: Swift-BAT refined analysis DATE: 17/05/25 18:53:59 GMT FROM: Amy Lien at GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J.G. Gropp (PSU), H. A. Krimm (NSF/USRA), 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-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170524A (trigger #754322) (Gropp et al., GCN Circ. 21135). The BAT ground-calculated position is RA, Dec = 319.488, 48.603 deg which is RA(J2000) = 21h 17m 57.2s Dec(J2000) = +48d 36' 12.5" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%. The mask-weighted light curve shows a double peaked structure with the first pulse from ~T0 to ~T+0.05, and second pulse from ~T+0.05 to ~T+0.1. T90 (15-350 keV) is 0.10 +- 0.02 sec (estimated error including systematics). The time-averaged spectrum from T+0.00 to T+0.12 sec fit by a simple power-law model shows the power law index of 1.07 +- 0.24 (chi squared 47.68 for 57 d.o.f.). The fluence in the 15-150 keV band is 3.7 +- 0.6 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. A single blackbody fit to the time-averaged spectrum shows the blackbody temperature of 21.09 +- 3.99 keV (chi squared 51.91 for 57 d.o.f.). A thermal bremsstrahlung model fit shows the temperature of 199.36 +- -80.44 keV (chi squared 57.87 for 57 d.o.f.). A double blackbody fit shows the lower temperature of 5.84 (error not unconstrained) keV and the higher temperature of 25.96 +15.56 keV (chi squared 45.99 for 55 d.o.f.). All the quoted errors are at the 90% confidence level. The photon index of ~ 1 using the simple power-law model is consistent with those from the BAT-detected short GRBs (Lien & Sakamoto et al. 2016), and harder than the spectra of many BAT-detected SGRs, which have photon index ~ 3. In addition, the double-peaked structure seen in this burst is not commonly observed in the BAT light curves of SGRs (with time bins >= 2 ms). The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/754322/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21145 SUBJECT: GRB 170524A: TSHAO and CrAO optical observations DATE: 17/05/25 20:28:02 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), S. Nazarov (CrAO), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 170524A (trigger=754322) (Gropp et al., GCN 21135) with Zeiss-1000 (East) of Tien Shan Astronomical Observatory and AZT-8 telescope of CrAO. We obtained several images in R filter. The TSHAO observations started on 2017-05-24 (UT) 20:31:45 under not optimal weather conditions. Observations in CrAO started on 2017-05-25 (UT) 00:18:50. Within enhanced XRT position (Evans et al. GCN 21136) we did not detect any optical source in the first epoch. In the second epoch (CrAO observation) we detected an object which is on the edge of the enhanced XRT position. The object has coordinates (J2000) 21:17:56.30 +48:36:27.9 with uncertainties of about 1 arcsec in each coordinate and brightness of R=20.10 +/- 0.15 at 0.1992 days after the Swift trigger. For now we can not say anything about the object variability. However the object is barely visible in DSS2 (Red). The preliminary results of field photometry are as follows Date UT start t-T0 Filter Exp. UL(3 sigma) (mid, days) (s) 2017-05-24 20:31:45 0.06857 R 46*120 20.3 2017-05-25 00:18:50 0.19920 R 10*180 21.5 Photometry is based on nearby USNO-B1.0 stars USNO-B1.0_id R2 1386-0392957 16.69 1385-0394718 17.29 1386-0392907 17.11 The finding chart of the object can be found at http://grb.rssi.ru/GRB170524A/GRB170524A_CrAO_170524.png //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21152 SUBJECT: GRB 170524A: RATIR Optical and NIR Observations DATE: 17/05/26 19:08:59 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 170524A (Gropp, et al., GCN 21135) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2017/05 25.40 to 2017/05 25.46 UTC (13.79 to 15.29 hours after the BAT trigger), obtaining a total of 1.06 hours exposure in the r and i bands and 0.36 hours exposure in the Z, Y, J, and H bands. We again observed from 2017/05 26.32 to 2017/05 26.47 UTC (35.77 to 39.48 hours after the BAT trigger), obtaining a total of 2.42 hours exposure in the r and i bands and 1.01 hours exposure in the Z, Y, J, and H bands. For a source within the Swift-XRT error circle (Evans, et al., GCN 21136), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following upper limits (3-sigma): 5/25 5/26 r > 24.45 > 25.66 i > 23.25 > 24.52 Z > 21.72 > 23.00 Y > 21.26 > 22.57 J > 18.16 > 21.25 H > 17.83 > 21.50 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21212 SUBJECT: GRB 170524A: 15 GHz upper limits from AMI DATE: 17/06/07 22:38:43 GMT FROM: Kunal Mooley at Oxford U K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester) The AMI Large Array robotically triggered on the Swift alert for GRB 170524A (Gropp et al., GCN 21135) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2016 May 25.03, May 26.26, May 28.18 and Jun 01.20 (UT) do not reveal any radio source at the XRT location (Evans et al., GCN 21136), with 3sigma upper limits of 162 uJy, 207 uJy, 120 uJy and 126 uJy respectively. We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.