//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20846 SUBJECT: GRB 170311A: Swift detection of a burst DATE: 17/03/11 08:25:14 GMT FROM: David Palmer at LANL J. R. Cummings (NASA/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 08:08:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170311A (trigger=741965). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 280.563, -30.063 which is RA(J2000) = 18h 42m 15s Dec(J2000) = -30d 03' 45" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 15 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 08:10:28.0 UT, 105.1 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 280.5893, -30.0458 which is equivalent to: RA(J2000) = 18h 42m 21.43s Dec(J2000) = -30d 02' 44.8" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 102 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 consistent with the Galactic value of 1.30 x 10^21 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 109 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 none of the XRT error circle. 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 expected extinction corresponding to E(B-V) of 0.16. 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: 20847 SUBJECT: GRB 170311A: MASTER-OAFA early optical observations DATE: 17/03/11 10:01:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) , National University of San Juan, Argentina H. Levato, C. Saffe Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, A.V.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk, O. Ershova Irkutsk State University V.Yurkov, Yu.Sergienko Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory 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 OAFA was pointed to the GRB170311A 18 sec after notice time and 59 sec after trigger time (Cummings et al., GCN 20846) at 2017-03-11 08:09:45 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box (ra=280.562 dec=-30.0628 r=0.05). The 5-sigma upper limit has been about 16.2 mag The observations made on zenit distance = 49 degrees, galaxy latitude b = -12 degree. The moon (98 % bright part) is 15 degrees above the horizon. The distance between moon and object is 124 The sun altitude is -30.1 degree. The object can be observed till sunrise at 2017-03-11 10:34:12 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20848 SUBJECT: GRB 170311A: GROND upper limits DATE: 17/03/11 15:45:09 GMT FROM: Patricia Schady at MPE/Swift P. Schady and P. Wiseman (both MPE Garching) report: We observed the field of GRB 170311A (Swift trigger 20846; Cummings et al., GCN #20846) 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 09:45 UT on 2017-03-11, 1.6 hours after the GRB trigger. They were performed at an average seeing of 1.2" and at an average airmass of 1.1. We do not detect a source within the Swift-XRT error circle (Cummings et al., GCN #20846) down to the following 3 sigma limiting AB magnitudes: g' > 23.1 mag r' > 23.4 mag i' > 22.7 mag z' > 22.5 mag J > 20.6 mag H > 20.2 mag K > 19.0 mag The given limits are derived based on images calibrated against Pan-STARRS/2MASS field stars, and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.14 in the direction of the burst (Schlafly & Finkbeiner 2011). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20850 SUBJECT: GRB 170311A: Enhanced Swift-XRT position DATE: 17/03/11 22:53:52 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 2232 s of XRT Photon Counting mode data and 3 UVOT images for GRB 170311A, 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 = 280.58942, -30.04597 which is equivalent to: RA (J2000): 18h 42m 21.46s Dec (J2000): -30d 02' 45.5" with an uncertainty of 1.5 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: 20851 SUBJECT: GRB 170311A: Swift/UVOT Upper Limits DATE: 17/03/12 02:10:46 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) 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 170311A 110 s after the BAT trigger (Cummings et al., GCN Circ. 20846). No optical afterglow consistent with the XRT position (Cummings et al. GCN Circ. 20846) 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 110 259 147 >20.5 u_FC 269 519 246 >19.7 white 110 7074 645 >21.2 v 600 11424 1022 >20.3 b 525 5585 294 >20.1 u 269 5380 537 >20.1 w1 650 5175 279 >20.1 m2 624 13058 82 >20.1 w2 575 7280 313 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.16 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20852 SUBJECT: GRB 170311A: Swift-XRT refined Analysis DATE: 17/03/12 03:29:38 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), A. Cholden-Brown (PSU), S. J. LaPorte (PSU), K.L. Page (U. Leicester), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 170311A, from 108 s to 35.6 ks after the BAT trigger. The data comprise 64 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=1.59 (+0.16, -0.17). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.52 (+0.28, -0.26). The best-fitting absorption column is 2.2 (+1.5, -0.9) x 10^21 cm^-2, consistent with the Galactic value of 1.3 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 (5.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+1.5, -0.9) x 10^21 cm^-2 Galactic foreground: 1.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.52 (+0.28, -0.26) If the light curve continues to decay with a power-law decay index of 1.59, the count rate at T+24 hours will be 6.1 x 10^-5 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.9 x 10^-15 (3.4 x 10^-15) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00741965. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20853 SUBJECT: GRB 170311A: Further GROND analysis DATE: 17/03/12 14:20:10 GMT FROM: Philip Wiseman at MPE/Swift P. Wiseman and P. Schady (both MPE Garching) report: We re-inspected the observations of GRB 170311A taken with GROND (Schady & Wiseman, GCN #20848) with respect to the enhanced XRT position (Osborne et al., GCN #20850). There is no credible afterglow consistent with or near to this position. The upper limits remain the same as those reported in GCN #20848. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20855 SUBJECT: GRB 170311A: Swift-BAT refined analysis DATE: 17/03/12 16:08:13 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), N. Gehrels (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), (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 170311A (trigger #741965) (Cummings, et al. GCN Circ. 20846). The BAT ground-calculated position is RA, Dec = 280.539, -30.041 deg which is RA(J2000) = 18h 42m 09.4s Dec(J2000) = -30d 02' 27.1" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%. The mask-weighted light curve shows a complex structure with several overlapping peaks that starts at ~T-1 s and ends at ~T+6 s. T90 (15-350 keV) is 6.32 +- 0.96 sec (estimated error including systematics). The time-averaged spectrum from T-0.92 to T+6.08 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.38 +- 0.32. The fluence in the 15-150 keV band is 2.5 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.73 sec in the 15-150 keV band is 0.8 +- 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/741965/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20858 SUBJECT: GRB 170311A: VLT observations DATE: 17/03/13 12:54:51 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. Malesani (DARK/NBI), H. Flores (GEPI/Paris obs.), A. J. Levan (Univ. Warwick), D. Xu (NAOC/CAS), N. R. Tanvir (Univ. Leicester), and J. P. U. Fynbo (DARK/NBI), report: We observed the field of GRB 170311A (Cummings et al., GCN 20846) with the VLT/UT2 (Kueyen), using the acquisition camera of the X-shooter spectrograph. Observations started approximately on March 11.366 UT, that is around 38 min after the GRB trigger. Imaging was carried out using the SDSS z filter. No source is detected within or close to the UVOT-enhanced XRT position (Osborne et al., GCN 20850), down to a 3-sigma limiting magnitude z = 21 AB, calibrated against nearby stars from the Pan-STARRS catalog (Chambers et al. 2016, arXiv: 1612.05560). Our result is consistent with other reports (e.g., Wiseman & Schady, GCN 20853). We acknowledge excellent support from the ESO observing staff at Paranal, in particular Marcelo Lopez, Joe Anderson, and George Hau. We also acknowledge the team of the Gaia-ESO survey (ESO program 197.B-1074, PI Gilmore), for generously and consistently accepting to carry out ToO observations during their allocated nights.