//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19577 SUBJECT: GRB 160625A: Swift detection of a burst DATE: 16/06/25 22:56:43 GMT FROM: Scott Barthelmy at NASA/GSFC A. Maselli (INAF-IASFPA), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 22:40:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160625A (trigger=701503). Swift did not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 176.937, -65.114, which is RA(J2000) = 11h 47m 45s Dec(J2000) = -65d 06' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several peaks in the first 40 sec and then a large peak at T+170 sec structure with a duration of at least 180 sec. The peak count rate was ~14000 counts/sec (15-350 keV), at ~175 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+20.3 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is A. Maselli (maselli AT ifc.inaf.it). 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: 19578 SUBJECT: GRB 160625A: Swift-XRT observations DATE: 16/06/25 23:51:03 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB), G. Cusumano (INAF-IASF PA), P.A. Evans (U. Leicester) and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 160625A at 23:02:36.8 UT, 1325.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 176.91418, -65.14362 which is equivalent to: RA(J2000) = 11h 47m 39.40s Dec(J2000) = -65d 08' 37.0" with an uncertainty of 5.8 arcseconds (radius, 90% containment). This location is 112 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. No spectrum from the promptly downlinked event data is yet available to determine the column density. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19579 SUBJECT: GRB 160625A - two different events? DATE: 16/06/26 00:01:31 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann (TLS Tautenburg) speculates: Swift just triggered on GRB 160625A (Swift Trigger 701503, Maselli et al., GCN #19577). They reported several rather small peaks followed by very strong emission ca. three minutes later. This burst is seen to be extremely powerful in INTEGRAL SPI ACS and CALET GBM. It seems to have begun with a short spike at about the same time as the Swift BAT trigger (Fermi GBM trigger 488587220). Three minutes later, Fermi LAT sent out a flight position at: RA = 308.267 Dec. = +6.900 with an error of 0.5 degrees. This position differs very strongly from the Swift BAT position. (Dec. of -65!) Additionally, Swift BAT has recently slewed to the BAT position and found a faint X-ray afterglow (Burrows et al., GCN 19578), which is in contrast to the very bright one one would expect from the extreme burst seen by INTEGRAL and CALET. I suggest that these are two different events, with the bright GRB seen through side of the Swift spacecraft. The Fermi LAT position is affected by a relatively low amount of extinction (E_(B-V)=0.1), in contrast to the Swift position (E_(B-V)=1.3). I strongly urge observations of the LAT position by Swift to determine an XRT position, and by optical observatories as well. Judging from the INTEGRAL SPI ACS light curve, this GRB is of similar intensity to GRB 160623A. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19583 SUBJECT: GRB 160625A: Enhanced Swift-XRT position DATE: 16/06/26 04:35:51 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 830 s of XRT Photon Counting mode data and 3 UVOT images for GRB 160625A, 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 = 176.91548, -65.14460 which is equivalent to: RA (J2000): 11h 47m 39.72s Dec (J2000): -65d 08' 40.6" with an uncertainty of 2.5 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19591 SUBJECT: GRB 160625A: Swift-XRT refined Analysis DATE: 16/06/26 17:22:41 GMT FROM: Phil Evans at U of Leicester P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and A. Maselli report on behalf of the Swift-XRT team: We have analysed 6.4 ks of XRT data for GRB 160625A (Maselli et al. GCN Circ. 19577), from 1.3 ks to 48.7 ks after the BAT trigger. The data comprise 1.7 ks in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 19583). The late-time light curve (from T0+7.4 ks) can be modelled with a power-law decay with a decay index of alpha=0.71 (+0.31, -0.28). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+/-0.5). The best-fitting absorption column is 2.2 (+0.9, -0.7) x 10^22 cm^-2, in excess of the Galactic value of 1.0 x 10^22 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.8 x 10^-11 (1.6 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+0.9, -0.7) x 10^22 cm^-2 Galactic foreground: 1.0 x 10^22 cm^-2 Excess significance: 2.8 sigma Photon index: 2.2 (+/-0.5) If the light curve continues to decay with a power-law decay index of 0.71, the count rate at T+24 hours will be 9.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-13 (1.6 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00701503. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19592 SUBJECT: GRB 160625A: Swift-BAT refined analysis DATE: 16/06/26 17:23:45 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA), 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 downlinks, we report further analysis of BAT GRB 160625A (trigger #701503) (Maselli, et al., GCN Circ. 19577). The BAT ground-calculated position is RA, Dec = 176.939, -65.142 deg, which is RA(J2000) = 11h 47m 45.3s Dec(J2000) = -65d 08' 30.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 57%. The mask-weighted light curve shows at least 7 peaks, the first starting at ~T-35 sec, the brightest peak at ~T+36 sec, and the last peak ending at ~T+70 sec. The peak mentioned in GCN Circ 19577 at T+170 sec is due to GRB 160625B (as suggested by Kann, Circ 19579) and confirmed by our analysis. T90 (15-350 keV) is 53.9 +- 3.1 sec (estimated error including systematics). The time-averaged spectrum from T-15.04 to T+47.41 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.08 +- 0.07. The fluence in the 15-150 keV band is 3.3 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+35.07 sec in the 15-150 keV band is 3.0 +- 0.2 ph/cm2/sec. 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/701503/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19593 SUBJECT: GRB 160625A: Swift/UVOT Upper Limits DATE: 16/06/26 20:48:32 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (UCL-MSSL) and A. Maselli (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160625A 7183 s after the BAT trigger (Maselli et al., GCN Circ. 19577). No optical afterglow consistent with the XRT position (Burrows et al. GCN Circ. 19578) is detected in the UVOT exposures. We note the presence of a source approximately 3'' from the XRT position. This source is present in the USNO catalogue. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 7183 7952 344 >20.8 v 8163 8363 197 >19.0 b 7548 7747 197 >19.9 u 7342 7542 197 >19.4 m2 8368 8483 113 >18.9 w2 7958 8158 197 >19.6 The magnitudes in the table are not corrected for the substantial Galactic extinction due to the reddening of E(B-V) = 1.51 in the direction of the burst (Schlegel et al. 1998). -- Dr. Massimiliano De Pasquale Research associate - Swift UVOT scientist Mullard Space Science Laboratory, University College London //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19629 SUBJECT: GRB 160625A: GROND upper limits DATE: 16/06/30 11:29:31 GMT FROM: Ting-Wan Chen at MPE T. Schweyer, T.-W. Chen, and J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 160625A (Swift trigger 701503; Maselli et al., GCN #19577) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 22:55 UT on 2016-06-26, 24.24 hrs after the GRB trigger. They were performed through cirrus at an average seeing of 1.4" and at an average airmass of 1.2. We do not detect any source within the Swift-XRT error circle reported by Burrows et al. (GCN #19578) down to g > 22.6 mag, r > 23.9 mag, i > 22.5 mag, z > 22.6 mag, J > 19.9 mag, H > 19.4 mag, K > 19.5 mag. Given magnitudes are calibrated against USNO as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=1.2 mag in the direction of the burst (Schlafly and Finkbeiner 2011). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19661 SUBJECT: GRB 160623A: Astrosat CZTI detection DATE: 16/07/06 06:58:47 GMT FROM: Varun Bhalerao at IUCAA V. Bhalerao (IUCAA), V. Kumar (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration: Analysis of Astrosat data showed the detection of very bright GRB 160623A (Fermi-LAT detection: Vianello et al., GCN 19553, Mailyan et al., GCN 19555; Mingo et al. GCN 19558; Frederiks et al. GCN 19554) The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak at UT 04:59:45.0, 49.23 seconds before the fermi trigger At 05:00:34.23 (trigger 488350837 / 160623209). The peak count rate was 2940 counts/sec above the background (four quadrants summed together), with a total of 20385 counts. The local mean background count rate of 193.2 is counts/sec. Using cumulative rates, we measure a T90 of 14.2 sec. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=node/9 . CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. [GCN OPS NOTE(07jul16): Per operator, the GRB name as corrected from 1600625 to 160625.]