//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17874 SUBJECT: GRB 150527A: Swift detection of a burst DATE: 15/05/27 07:03:59 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U Leicester), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 06:48:55 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150527A (trigger=641698). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 288.958, +4.194 which is RA(J2000) = 19h 15m 50s Dec(J2000) = +04d 11' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 06:49:57.6 UT, 61.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 288.9599, 4.2013 which is equivalent to: RA(J2000) = 19h 15m 50.39s Dec(J2000) = +04d 12' 04.7" with an uncertainty of 2.3 arcseconds (radius, 90% containment). This location is 27 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 gives a column density consistent with the Galactic value of 5.67 x 10^21 cm^-2 (Willingale et al. 2013). 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 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: 17876 SUBJECT: GRB 150527A: RATIR Afterglow Detection DATE: 15/05/27 08:04:18 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), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 150527A (Evans, et al., GCN 17874) 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 2015/05 27.29 to 2015/05 27.32 UTC (13.2 to 54.6 minutes after the BAT trigger), obtaining a total of 0.58 hours exposure in the r, i, and z bands. A source is detected within the Swift-XRT error circle. In comparison with the USNO-B1 catalog, we obtain the following detections and upper limit (3-sigma): r 21.17 +/- 0.10 i 20.83 +/- 0.14 z > 19.50 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Additional observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17877 SUBJECT: GRB 150527A: LCOGT McDonald observations DATE: 15/05/27 09:02:38 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy J. Japelj (U. Ljubljana), C. Guidorzi (U. Ferrara), C.G. Mundell (U. Bath), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of a larger collaboration report: The 1-m LCOGT McDonald unit began observing Swift GRB 150527A (Evans al GCN 17874) on May 27 at 06:56:33 UT (~7.6 minutes after the burst trigger) with SDSS r and i filters. Inside the Swift-XRT error circle we provide conservative limits on detection down to the following limiting magnitudes: Mid Time Exposure Filter Magnitude (s) (s) --------------------------------------------------- 795 5x120 r' > 19.5 1500 5x120 i' > 18.3 --------------------------------------------------- These values are compatible with the source reported by RATIR (Butler et al. GCN 17876), although no information about its position is reported. We note the presence of a faint source in our coadded image with i'=20.6 +- 0.4 mag at the following position: RA(J2000)=19:15:50.31, Dec(J2000)= +04:12:05.0. However, we caution that the field is crowded, Galactic dust extinction towards this field is high, A_V = 2.7 mag (Schlafly et al. 2011). Calibration is done against nearby USNOB-1 stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17878 SUBJECT: GRB 150527A: Fermi GBM observation DATE: 15/05/27 14:29:39 GMT FROM: Hoi-Fung Yu at MPE H.-F. Yu (MPE) reports on behalf of the Fermi GBM Team: "At 06:47:08.70 UT on 27 May 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150527A (trigger 454402031 / 150527283), which was also detected by Swift (Evans et al. 2015, GCN 17874). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 89 degrees. The GBM light curve shows one single pulse with a duration (T90) of about 9.2 s (50-300 keV). The time-averaged spectrum from T0-3.072 s to T0+7.168 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.76 +/- 0.20 and the cutoff energy, parameterized as Epeak, is 319 +/- 97 keV. The event fluence (10-1000 keV) in this time interval is (2.2 +/- 0.4)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+2.304 s in the 10-1000 keV band is 2.1 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17879 SUBJECT: GRB 150527A: Enhanced Swift-XRT position DATE: 15/05/27 16:33:45 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 2996 s of XRT Photon Counting mode data and 4 UVOT images for GRB 150527A, 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 = 288.95986, +4.20196 which is equivalent to: RA (J2000): 19h 15m 50.37s Dec (J2000): +04d 12' 07.0" with an uncertainty of 1.6 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: 17880 SUBJECT: GRB 150527A: Swift-BAT refined analysis DATE: 15/05/27 16:47:04 GMT FROM: Scott Barthelmy at NASA/GSFC A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/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-239 to T+711 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150527A (trigger #641698) (Evans, et al., GCN Circ. 17874). The BAT ground-calculated position is RA, Dec = 288.962, 4.195 deg, which is RA(J2000) = 19h 15m 50.9s Dec(J2000) = +04d 11' 41.0" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted light curves shows a multi-peak event starting at ~T-45 sec, with the brightest peak at ~T-14, and ending at T+25 sec. T90 (15-350 keV) is 112 +- 80 sec (estimated error including systematics). The time-averaged spectrum from T-111.44 to T+16.56 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.69 +- 0.10. The fluence in the 15-150 keV band is 3.1 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-7.94 sec in the 15-150 keV band is 0.3 +- 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/641698/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17881 SUBJECT: GRB150527A: REM - NIR afterglow DATE: 15/05/27 18:21:19 GMT FROM: Eliana Palazzi at IASF/CNR,Bologna L. Nicastro, E. Palazzi, A. Rossi (INAF/IASF Bologna), D. Fugazza (INAF/OAB) on behalf of the REM team: We observed the field of the GRB150527A (Evans et al., GCN 17874) simultaneously in the optical (griz) and near infrared (H) bands with the 60-cm robotic telescope REM at La Silla Observatory (Chile). The observations started about 1 min after the GRB trigger. An uncatalogued source in the enhanced XRT error box (Evans et al., GCN 17879) is detectedi, only in the H images, at the coordinates: RA(J2000) = 19:15:50.31 DEC(J2000) = +04:12:06.1 Possibly this is the same source mentioned by Butler et al. (GCN 17876). A very preliminary photometry, calibrated against 2MASS, indicates that the object faded from H = 14.8 +/- 0.2 in the first image to H = 15.2 +/- 0.2 about 5 min later. Thus we identify this source as the NIR afterglow of the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17882 SUBJECT: GRB 150527A: Swift/UVOT Upper Limits DATE: 15/05/27 21:46:10 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150527A 68 s after the BAT trigger (Evans et al., GCN Circ. 17874). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 17879) or with the RATIR or REM sources (Butler et al., GCN Circ. 17876 and Nicastro et al., GCN Circ. 17881) 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 68 218 147 >20.2 u_FC 280 523 240 >19.1 white 10385 11927 1542 >21.2 v 4315 4515 197 >18.8 b 3700 10380 1082 >20.8 u 280 6271 623 >19.6 w1 5920 6120 197 >19.4 w2 4110 12019 281 >19.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.97 in the direction of the burst (Schlegel et al. 1998). We note however that the value for extinction could be unreliable at this position. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17883 SUBJECT: GRB 150527A: MITSuME Okayama upper limits DATE: 15/05/28 00:20:58 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of MITSuME and OISTER collaboration: We observed the field of GRB 150527A (Evans et al., GCNC 17874) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2015-05-27 12:57:14 UT (~6.1 h after the burst). We could not detect the previously reported afterglow (Butler et al., GCNC 17527) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' Rc Ic ----------------------------------------------------- 0.29760 13:57:27 5760.0 >19.5 >19.2 >18.3 ----------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17884 SUBJECT: GRB 150527A: Swift-XRT refined Analysis DATE: 15/05/28 07:04:04 GMT FROM: Phil Evans at U of Leicester A. Amaral-Rogers (U. Leicester), A. D'aì (INAF-IASFPA), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 3.7 ks of XRT data for GRB 150527A (Evans et al. GCN Circ. 17874), from 47 s to 22.7 ks after the BAT trigger. The data comprise 598 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 17879). The late-time light curve (from T0+3.7 ks) can be modelled with a power-law decay with a decay index of alpha=0.9 (+0.6, -0.4). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.4, -0.3). The best-fitting absorption column is 1.2 (+0.5, -0.4) x 10^22 cm^-2, in excess of the Galactic value of 5.7 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.8 x 10^-11 (9.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.2 (+0.5, -0.4) x 10^22 cm^-2 Galactic foreground: 5.7 x 10^21 cm^-2 Excess significance: 2.7 sigma Photon index: 2.0 (+0.4, -0.3) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00641698. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17885 SUBJECT: Konus-Wind observation of GRB 150527A DATE: 15/05/28 17:00:31 GMT FROM: Anastasia Tsvetkova at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 150527A (Swift-BAT trigger #641698: Evans, et al., GCN Circ. 17874; Lien, et al., GCN Circ. 17880; Fermi-GBM detection: Yu, GCN Circ.17878) was detected by Konus-Wind in the waiting mode. The burst light curve shows two emission episodes: the first episode (from ~T0(BAT)-108 s to ~T0(BAT)-99 s) triggered GBM, and the second (from ~T0(BAT)-22 s to ~T0(BAT)+4s), which triggered BAT. As observed by Konus-Wind, the burst had a fluence of 6.09(-0.62,+0.76)x10^-6 erg/cm2 and a 2.944-s peak flux, measured from ~T0(BAT)-13 s, of 3.10(-0.61,+0.65)x10^-7 erg/cm2/s (both in the 20 - 1000 keV energy range). Fitting the K-W 3-channel time-integrated spectrum (measured from ~T0(BAT)-108 s to ~T0(BAT)+4 s) by a simple power-law model yields the photon index -2.20(-0.10,+0.10), chi2=0.88/1 dof. Modelling the 3-channel spectrum near the peak count rate (from ~T0(BAT)-13 s to ~T0(BAT)-10 s) by the cutoff power law yields the following model parameters: the photon index alpha = -1.62(-0.31,+0.92), and the peak energy Ep = 107(-40,+100) keV. All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB150527A/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 17898 SUBJECT: GRB 150527A: Continued RATIR Observations DATE: 15/06/02 14:25:00 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), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 150527A (Evans, et al., GCN 17874) 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 initially from 2015/05 27.29 to 2015/05 27.45 UTC (0.17 to 4.06 hours after the BAT trigger), obtaining a total of 3.10 hours exposure in the r, i, and z bands and then again from 2015/05 28.25 to 2015/05 28.47 UTC (23.27 to 28.36 hours after the BAT trigger), obtaining a total of 3.91 hours exposure in the r, i, and z bands. The source we initially detected (Butler, et al., GCN 17876; RA, Dec = 19:15:50.27, 4:12:4.7; J2000, +/-0.5") in the Swift-XRT error circle (Evans, et al., GCN 17874) has not faded in our extended dataset and is, therefore, unlikely to be the afterglow. We note the REM source (Nicastro, et al., GCN 17881) is marginally detected in our first epoch observation with i=23.4 +/- 0.5, calibrated relative to the USNO-B1 catalog. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.