//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22457 SUBJECT: GRB 180305A: Fermi-LAT detection DATE: 18/03/05 15:32:53 GMT FROM: Magnus Axelsson at Stockholm U. M. Axelsson (KTH and Stockholm Univ.) and E. Bissaldi (Politecnico and INFN Bari), report on behalf of the Fermi-LAT team: At 09:26:08.66 UT on March 05, 2018, Fermi-LAT detected high-energy emission from GRB 180305A, which was also detected by Fermi-GBM (trigger 541934773 / 180305393). The best LAT on-ground location is found to be RA, Dec = 49.7, 32.1 (J2000) with an error radius of 0.12 deg (90 % containment, statistical error only). This location was a few degrees outside the LAT field of view at the time of the trigger. It entered the FoV approximately 200s later, and remained visible until around 2600s after the trigger time. The data from the Fermi-LAT show a significant increase in the event rate that is spatially correlated with the trigger with high significance. More than 10 events above 100 MeV are detected. The highest-energy photon is a 9 GeV event which is observed ~1630 seconds after the GBM trigger. A Swift ToO has been approved for this burst. The Fermi-LAT point of contact for this burst is Magnus Axelsson (magaxe@kth.se). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22458 SUBJECT: GRB 180305A: Fermi GBM detection DATE: 18/03/05 17:10:52 GMT FROM: Peter Veres at UAH P. Veres (UAH) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 09:26:08.66 UT on 05 March 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180305A (trigger 541934773 / 180305393) which was also detected by the Fermi LAT (Axelsson et al., GCN 22457). The GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 70 degrees. The GBM light curve consists of a single bright pulse with a duration (T90) of about 12.5 s (50-300 keV). The time-averaged spectrum from T0 to T0+24.1 s is best fit by a Band function with Epeak= 334 +/- 10 keV, alpha = -0.48 +/- 0.02 and beta = 2.29 +/- 0.07. The event fluence (10-1000 keV) in this time interval is (3.302 +/- 0.023)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.65 s in the 10-1000 keV band is 32.2 +/- 0.5 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: 22459 SUBJECT: GRB 180305A: Swift ToO observations DATE: 18/03/05 18:06:15 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/LAT GRB 180305A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020789 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/LAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22460 SUBJECT: GRB 180305A: RATIR Optical Afterglow Candidate DATE: 18/03/06 11:24:41 GMT FROM: Eleonora Troja at GSFC Eleonora Troja (GSFC), 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), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of the LAT GRB 180305A (Axelsson, et al., GCN 22457) 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 2018/03 6.11 to 2018/03 6.20 UTC (17.28 to 19.45 hours after the burst), obtaining a total of 1.36 hours exposure in the r and i bands. At the position of source #2 found by Swift-XRT  (Evans, et al., GCN 22459), we detect a faint uncatalogued optical source. In comparison with the USNO-B1 catalog, we obtain the following detections:   r    = 21.95 +/- 0.12   i    = 21.48 +/- 0.08 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source is located at RA,Dec = 03:18:28.33,+32:06:36.2 (J2000, +/-0.5"). Further observations to establish fading of the optical source are planned. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22461 SUBJECT: Konus-Wind observation of GRB 180305A DATE: 18/03/06 14:42:58 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, bright GRB 180305A (Fermi-LAT detection: Axelsson and E. Bissaldi, GCN Circ. 22457; Fermi-GBM detection: Veres and von Kienlin, GCN Circ. 22458) triggered Konus-Wind at T0=33967.647 s UT (09:26:07.647). The burst light curve shows a single emission episode which starts at ~T0-2.4 s and has a total duration of ~44 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180305_T33967/ As observed by Konus-Wind, the burst had a fluence of 8.43(-0.58,+0.59)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+3.168 s, of 2.02(-0.32,+0.32)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+16.128 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.51(-0.09,+0.10), the high energy photon index beta = -2.41(-0.17,+0.13), the peak energy Ep = 348(-27,+30) keV (chi2 = 139/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+4.352 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.25(-0.15,+0.17), the high energy photon index beta = -2.59(-0.44,+0.23), the peak energy Ep = 467(-56,+64) keV (chi2 = 113/81 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22462 SUBJECT: GRB 180305A: Swift-XRT afterglow detection DATE: 18/03/06 15:38:42 GMT FROM: Boris Sbarufatti at PSU P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 180305A (Axelsson et al. GCN Circ. 22457), collecting 4.7 ks of Photon Counting (PC) mode data between T0+30.6 ks and T0+53.0 ks. Four uncatalogued X-ray sources are detected, of which one ("Source 2") is above the RASS limit and fading with 3-sigma significance, and is therefore likely the GRB afterglow. Using 3574 s of PC mode data and 6 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 49.61821, +32.10994 which is equivalent to: RA (J2000): 03h 18m 28.37s Dec(J2000): +32d 06' 35.8" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position is 2.7 arcmin from the Fermi/LAT position. The light curve can be modelled with a power-law decay with a decay index of alpha=2.7 (+0.5, -0.8). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.5 (+/-0.4). The best-fitting absorption column is 4.7 (+3.2, -2.3) x 10^21 cm^-2, consistent with the Galactic value of 2.4 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 5.4 x 10^-11 (6.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.7 (+3.2, -2.3) x 10^21 cm^-2 Galactic foreground: 2.4 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.5 (+/-0.4) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020789. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020789. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22463 SUBJECT: GRB 180305A: Mondy optical observations DATE: 18/03/06 17:07:13 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of of larger GRB follow-up collaboration: We observed the field of LAT/Fermi GRB 180305A (Axelsson, et al., GCN 22457) and Konus-Wind (Svinkin et al., GC 22461) with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images in R-filter starting on Mar. 06 (UT) 12:35:17. The afterglow candidate (Troja et al., GCN 22460) is clearly detected within XRT/Swift error circle (D'Avanzo et al., GCN 22462). Preliminary photometry is following. Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2018-03-06 12:35:17 1.15219 R 30*120 22.69 0.15 23.7 The photometry is based on nearby USNO-B1.0 stars USNO-B1_id R2 1221-0050419 18.60 1221-0050432 16.39 1221-0050407 19.31 Since the source has faded in comparison with the previous observation (Troja et al., GCN 22460) we can confirm the afterglow of GRB 180305A. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22464 SUBJECT: GRB 180305A: Swift/UVOT Upper Limits DATE: 18/03/06 18:03:54 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (MSSL-UCL) and M. H. Siegel (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180305A 30621 s after the Fermi/LAT trigger (Axelsson et al., GCN Circ. 22457). No optical afterglow consistent with the enhanced XRT position (D'Avanzo et al., GCN Circ. 22462) or the RATIR and Mondy detections (Troja et al., GCN Circ. 22460; Mazaeva et al., GCN Circ. 22463) 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) in the initial exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 30808 52964 961 >21.4 u 30621 52533 2623 >20.7 v 30994 48392 712 >19.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.454 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22465 SUBJECT: GRB 180305A: RATIR Optical Observations DATE: 18/03/07 14:59:49 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 (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 (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 180305A (Axelsson, et al., GCN Circ. 22457) 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 2018/03 7.11 to 2018/03 7.20 UTC (41.30 to 43.46 hours after the BAT trigger), obtaining a total of 1.64 hours exposure in the r and i bands. The source reported by Troja et al. (GCN Circ. 22460) is still detected, but has faded to: r = 23.15 +/- 0.21 i = 22.80 +/- 0.15 These magnitudes are in the AB system, are calibrated against the USNO-B1 catalog, and are not corrected for Galactic extinction in the direction of the GRB. The combination of the optical fading reported here and the X-ray fading reported by D’Avanzo et al. (GCN Circ. 22462) confirm that this is the afterglow of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22467 SUBJECT: GRB 180305A CALET Gamma-Ray Burst Monitor detection DATE: 18/03/11 05:23:23 GMT FROM: Takanori Sakamoto at AGU A. V. Penacchioni (U of Florence), A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The long, bright GRB 180305A (Fermi-LAT detection: Axelsson & Bissaldi, GCN circ. 22457; Fermi-GBM detection: Veres & von Kienlin, GCN circ. 22458; Konus-Wind detection: Svinkin et al., GCN circ. 22461) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:26:09.218 UTC on 5 March 2018. No real time CGBM GCN notice was distributed about this trigger because the real time communication from the ISS was off (loss of signal) between 9:00 and 9:36. The burst signal was seen by all CGBM detectors. The burst light curve shows a single multi-peaked pulse which starts at T-0.5 sec, peaks at T+3.4 sec and ends at T+14.6 sec. The T90 and the T50 durations measured by the SGM data are 10.0 +- 0.8 sec and 3.88 +- 0.13 sec (40-1000 keV), respectively. CGBM HV was turned off at ~T+95 sec due to entering the radiation belts, so no CGBM data are available from that time until ~T+1300 sec. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1204276876/ On March 2, the CGBM on-board event data capture end time was changed from 8 sec to 512 sec, so from that time in the Event mode CGBM collects time tagged events up to T0+512 sec, where T0 is the trigger time. The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22476 SUBJECT: GRB 180305A: AstroSat CZTI detection DATE: 18/03/13 16:37:50 GMT FROM: Vidushi Sharma at IUCAA V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a bright GRB 180305A, which was also detected by Fermi/GBM (Veres P. et al., GCN 22458), Konus-Wind (Svinkin D. et al., GCN 22461), Swift/XRT (D'Avanzo P. et al., GCN 22462) and CALET (Penacchioni A. V. et al., GCN 22467). The source was clearly detected in the 40-200 keV energy range. The light curve shows single peak emission with strongest peak at 09:26:12.5 UT, ~4 s after Fermi/GBM trigger. The measured peak count rate is 427.3 cts/s above the background in combined data of four quadrants, with a total of 2358 cts. The local mean background count rate was 490.6 cts/s. Using cumulative rates, we measure a T90 of 8.9 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. 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.