//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19365 SUBJECT: GRB 160501A: Swift detection of a burst DATE: 16/05/01 00:58:55 GMT FROM: David Palmer at LANL J. R. Cummings (NASA/UMBC), A. P. Beardmore (U Leicester), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU) and T. N. Ukwatta (LANL) report on behalf of the Swift Team: At 00:40:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160501A (trigger=684679). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 286.377, -17.240 which is RA(J2000) = 19h 05m 30s Dec(J2000) = -17d 14' 22" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual for an image trigger, there is no clear variation visible in the immediately-available lightcurve data. The XRT began observing the field at 00:42:39.8 UT, 128.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 286.38344, -17.24088 which is equivalent to: RA(J2000) = 19h 05m 32.03s Dec(J2000) = -17d 14' 27.2" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 22 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.62 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.7 (+3.06/-2.65) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 1.08e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 136 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 upper limit is 19.6 magnitude. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The typical upper limit is 18.0. No correction has been made for the expected extinction corresponding to E(B-V) of 0.18. Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.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: 19366 SUBJECT: GRB 160501A: NOT optical and NIR observations DATE: 16/05/01 03:55:51 GMT FROM: Zach Cano at U of Iceland Z. Cano (Univ. Iceland), N. Tanvir (Univ. Leicester), D. Malesani (DARK/NBI) & J. Saario (NOT) report on behalf of a larger collaboration: We observed the field of GRB 160501A (Cummings et al.; GCN Circ. 19365) with the 2.5-m Nordic Optical Telescope equipped with the StanCam and the NOTCam, starting at 01:57 UT on 01 May 2016. We obtained 15 minutes in the I-band (StanCam) and 18 minutes in the H-band (NOTCam). In our co-added optical and NIR images we do not detect any new source within the XRT error circle to the following limits: I > 22.3 mag H > 19.0 mag These upper limits (Vega) are for a single point source in the GRB field, they are calibrated against the USNO-B1 (optical) and 2MASS (NIR) catalogues, and they have not been corrected for foreground extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19367 SUBJECT: GRB 160501A MASTER-NET early observations DATE: 16/05/01 09:23:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the GRB160501A 24 sec after notice time and 106 sec after trigger time at 2016-05-01 00:42:21 UT in two polarizations. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box (Cummings et al GCN 19365). The 5-sigma upper limit has been about 17.5 mag on single (20 s exposure) and 19.1 mag at coadd of first 10 images (with total exposure 780 s). Not very depth upper limits are explained by the proximity to the Moon. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19368 SUBJECT: GRB 160501A: TAROT Calern observatory optical observations DATE: 16/05/01 10:13:48 GMT FROM: Alain Klotz at IRAP-CNRS-OMP Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Laugier, R. (CNRS-ARTEMIS), Gendre B. (UVI - Etelman Obs.) report: We imaged the field of GRB 160501A detected by SWIFT (trigger 684679) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 50 min after the GRB trigger. The elevation of the field increased from 20 degrees above horizon and weather conditions were good. We co added images to increase detectivity: t1(s) t2(s) Rmag_lim Site 3594 5526 18.5 TAROT Calern 5526 7863 18.5 TAROT Calern Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon= 18.9676 lat=-10.7948 and the galactic extinction in R band is about 1.0 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19369 SUBJECT: GRB 160501A: Enhanced Swift-XRT position DATE: 16/05/01 15:20:19 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 2151 s of XRT Photon Counting mode data and 1 UVOT images for GRB 160501A, 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 = 286.38402, -17.24138 which is equivalent to: RA (J2000): 19h 05m 32.16s Dec (J2000): -17d 14' 29.0" with an uncertainty of 1.9 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: 19370 SUBJECT: GRB 160501A: RATIR Optical and NIR Observations DATE: 16/05/01 15:45:08 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), 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), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 160501A (Cummings et al., GCN Circ. 19365) 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 2016/05 1.33 to 2016/05 1.47 UTC (7.23 to 10.70 hours after the BAT trigger), obtaining a total of 1.73 hours exposure in the r and i bands and 0.66 hours exposure in the Z, Y, J, and H bands. For a source within the enhanced Swift-XRT error circle (Evans et al., GCN Circ. 19369), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper limits: r > 22.94 i > 22.76 Z > 21.69 Y > 21.22 J > 20.81 H > 19.90 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: 19371 SUBJECT: GRB 160501A: Swift-XRT refined Analysis DATE: 16/05/01 17:34:09 GMT FROM: Phil Evans at U of Leicester T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), C. Pagani (U. 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) and J.R. Cummings report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 160501A (Cummings et al. GCN Circ. 19365), from 118 s to 46.0 ks after the BAT trigger. The data comprise 161 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. 19369). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.76 (+/-0.16). At T+261 s the decay steepens to an alpha of 4.4 (+0.6, -0.3) before breaking again at T+918 s to a final decay with index alpha=0.26 (+0.36, -0.20). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.96 (+0.16, -0.15). The best-fitting absorption column is 2.9 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.06 (+0.25, -0.18) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.7, -0.0) x 10^21 cm^-2 Galactic foreground: 1.6 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.06 (+0.25, -0.18) If the light curve continues to decay with a power-law decay index of 0.26, the count rate at T+24 hours will be 7.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x 10^-13 (3.6 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/00684679. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19372 SUBJECT: GRB 160501A: Swift/UVOT Upper Limits DATE: 16/05/01 20:00:06 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and J. R. Cummings (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160501A 136s after the BAT trigger (Cummings et al., GCN Circ. 19365). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 19369) 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 136 286 147 >20.3 u_FC 295 544 246 >19.7 white 575 1543 245 >21.1 v 625 1594 117 >18.9 b 551 1518 97 >19.9 w1 674 1643 117 >19.2 m2 649 1618 117 >19.7 w2 600 1569 117 >19.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.18 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19373 SUBJECT: GRB 160501A: UKIRT near-IR upper limits DATE: 16/05/01 22:03:31 GMT FROM: Wen-fai Fong at U of Arizona W. Fong and P. Milne (University of Arizona) report: "We observed the field of GRB 160501A (Cummings et al., GCN 19365) with the Wide Field Camera (WFCAM) mounted on the 3.8-m United Kingdom Infrared Telescope (UKIRT) on Mauna Kea beginning on 2016 May 1.533 UT (12.1 hr post-burst). We obtained observations in the J- and K-bands in 0.75" seeing. Using the quick-look pipeline ORAC-DR, we do not detect any near-IR source in or around enhanced X-ray position (Evans et al., GCN 19369). Calibrated to 2MASS, we therefore place 3-sigma limits of J(AB)>19.7 mag and K(AB)>19.2 mag on the near-IR afterglow of GRB 160501A at 12.1 hr post-burst. We note that this analysis is preliminary and a final reduction of the images are expected to be at least ~1.5 mag deeper. We thank Tim Carroll, Watson Varricatt and Tom Kerr for their assistance in planning and executing these observations." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19374 SUBJECT: GRB 160501A: MITSuME Okayama upper limits DATE: 16/05/02 00:56:20 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 160501A (Cummings et al., GCNC 19365) 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 2016-05-01 17:18:31 UT (~16.6 h after the burst). We did not find any new point source within the enhanced XRT circle (Evans et al., GCNC 19369) 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 ----------------------------------------------------- 0.73280 18:15:45 5460.0 >19.4 >19.1 >18.3 ----------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19375 SUBJECT: GRB 160501A: GROND Upper limits DATE: 16/05/02 10:01:04 GMT FROM: Fabian Knust at MPE/GROND J. Bodensteiner, F. Knust, T. Schweyer , J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 160501A (Swift trigger 684679; Cummings et al., GCN #19365) 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 07:15 UT on 2016-05-01, 6h 35min after the GRB trigger. They were performed at an average seeing of 1.3" and at an average airmass of 1.09. We do not detect a source within the Swift-XRT error circle reported by Evans et al. (GCN #19369) down to g' > 24.8 mag, r' > 24.5 mag, i' > 23.8 mag, z' > 23.9 mag, J > 21.1 mag, H > 20.7 mag, and K > 19.1 mag. (all in AB). The given limits are derived based on calibration against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.18 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19376 SUBJECT: GRB 160501A: Swift-BAT refined analysis DATE: 16/05/02 13:46:06 GMT FROM: Takanori Sakamoto at AGU C. B. Markwardt (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), 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+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160501A (trigger #684679) (Cummings, et al., GCN Circ. 19365). The BAT ground-calculated position is RA, Dec = 286.389, -17.249 deg which is RA(J2000) = 19h 05m 33.2s Dec(J2000) = -17d 14' 54.8" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 81%. The mask-weighted light curve a broad peak starting from T-80 sec, peaking at T+50 sec and ending at T+90 sec. T90 (15-350 keV) is 118 +- 19 sec (estimated error including systematics). The time-averaged spectrum from T-54.3 to T+72.6 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.6 +- 1.3, and Epeak of 28 +- 9 keV (chi squared 54.26 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 9.5 +- 1.3 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T-54.38 sec in the 15-150 keV band is 0.5 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.4 +- 0.2 (chi squared 63.09 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/684679/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19378 SUBJECT: GRB 160501A: SMARTS optical/IR observations DATE: 16/05/03 15:18:43 GMT FROM: Bethany Cobb at GWU B. E. Cobb (GWU) reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 160501A (GCN 19365, Cummings et al.) with a mid-exposure time of 4.3 hours post-burst (2016-05-01 05:01 UT). Total summed exposure times amounted to 36 minutes in I and 30 minutes in J. No source is detected at the position of the X-ray afterglow (GCN 19365, Cummings et al; GCN 19369, Evans et al.) to approximate limiting magnitudes of I > 20.7 and J > 18.5. Magnitudes are calibrated using USNO-B1.0 stars in I, and 2MASS stars in J.