//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18228 SUBJECT: GRB 150902A: Fermi-LAT detection DATE: 15/09/03 07:19:06 GMT FROM: Magnus Axelsson at Stockholm U. GRB 150902A: Fermi-LAT detection M. Arimoto (Tokyo Tech), M. Axelsson (KTH Stockholm), J. Racusin (NASA/GSFC), E. Bissaldi (INFN Bari), D. Kocevski (NASA/GSFC) report on behalf of the Fermi-LAT team: At 17:35:39.37 UT on 2015-09-02, Fermi-LAT detected high-energy emission from GRB 150902A, which was also detected by Fermi-GBM (trigger 462908143/150902733). The best LAT on-ground location is found to be RA, Dec = 214.926, -69.361 degrees (J2000) with an error radius of 0.127 deg (90% containment, systematic error only). This was 38 deg from the LAT boresight at the time of the trigger and triggered an autonomous repoint of the spacecraft. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM emission. More than 50 photons above 100 MeV and 9 photons above 1 GeV were observed within 300 seconds. The highest-energy photon is a 11 GeV event which is observed ~100 seconds after the GBM trigger. A Swift ToO has been requested for this burst. The Fermi-LAT point of contact for this burst is Daniel Kocevski (daniel.kocevski@nasa.gov). 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: 18229 SUBJECT: GRB 150902A: Fermi GBM detection DATE: 15/09/03 09:32:09 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD) and G. Younes (GWU) report on behalf of the Fermi GBM team: "At 17:35:39 UT on September 2nd 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150902A (trigger 462908143/150902733), which was also detected by Fermi-LAT (Axelsson et al. 2015, GCN 18228). The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software due to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. Both the GBM in-flight and on-ground locations are consistent with the LAT position. The GBM light curve consists of a series of unresolved pulses, with a duration of about 14 s (50-300 keV). The time-averaged spectrum from T0+3.0s to T0+17.0s is well fit by a Band function with Epeak = 351.40 +/- 5.61 keV, Alpha =-0.48 +/- 0.02 and Beta = -2.32 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (8.221 +/- 0.043)E-05 erg/cm^2. The 1.024 s peak photon flux measured starting from T0+8.8s in the 10-1000 keV band is 61.9 +/- 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: 18230 SUBJECT: GRB 150902A: Swift ToO observations DATE: 15/09/03 10:17:16 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 150902A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020549 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: 18233 SUBJECT: Konus-Wind observation of GRB 150902A DATE: 15/09/03 16:00:52 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, very bright GRB 150902A (Fermi LAT detection: Arimoto et al., GCN Circ. 18228; Fermi GBM detection: Roberts and Younes, GCN Circ. 18229) triggered Konus-Wind at T0=63340.850 s UT (17:35:40.850). The burst light curve shows a single pulse with a total duration of ~20 s followed by a weak tail up to ~100 s. The emission is seen up to ~18 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150902_T63340/ As observed by Konus-Wind, the burst had a fluence of 1.21(-0.07,+0.07)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+6.384 s, of 2.13(-0.27,+0.28)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+25.600 s) is best fit in the 20 keV - 18 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.58(-0.06,+0.07), the high energy photon index beta = -2.30(-0.11,+0.09), the peak energy 322(-21,+23) keV (chi2 = 138/96 dof) The spectrum near the maximum count rate (measured from T0+6.144 to T0+6.656 s) is best fit in the 20 keV - 11 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.02(-0.18,+0.21), the high energy photon index beta = -2.75(-0.39,+0.23), the peak energy 288(-33,+37) keV (chi2 = 77/47 dof) All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18234 SUBJECT: GRB 150902A: MASTER-SAAO optical observations DATE: 15/09/03 16:56:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, E.Popova, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk V.Krushinski, I.Zalozhnih Ural Federal University, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Carlos Lopez, Claudio Mallamaci and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was firstly pointed to the GRB150902A (Roberts et. al. GCN 18229) 67 sec after trigger time at 2015-09-02 17:36:47 UT. On our first (10s exposure) set we not found optical transient within FERMI error-box (ra=16 24 36 dec=-72 54 35 r=2.140000) brighter then 15.27. MASTER-SAAO robotic telescope makes several alert and inspect observations inside actual (at that time) FERMI GBM error boxes, but all of that frames located far away from the final FERMI LAT (Arimoto et. al GCN 18228) error box and did not cover it. MASTER-VWF very wide fileld cameras placed in MASTER-SAAO cover FERMI LAT error box at 2015-09-02 17:36:32.0 i.e. 47 sec after notice and 53 sec after trigger time, and imaging it continuously without time gaps till 2015-09-02 17:43:00. We have not find OT inside FERMI LAT error box with upper limit 11.5m on single (5 second) and 12.8m ( on coadd of 12 frames with total exposure 60 s) images. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18237 SUBJECT: GRB 150902A: Swift-XRT observations DATE: 15/09/04 14:55:37 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli (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 150902A (Arimoto et al. GCN Circ. 18228), collecting 4.9 ks of Photon Counting (PC) mode data between T0+59.6 ks and T0+78.6 ks. Two uncatalogued X-ray sources have been detected inside or close to the Fermi/LAT error region, however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 1: RA (J2000.0): 214.9797 = 14:19:55.13 Dec (J2000.0): -69.3535 = -69:21:12.6 Error: 4.4 arcsec (radius, 90% conf.) Count-rate: 0.0116 +/- 0.0022 ct s^-1 Flux: (5.16 +/- 0.98)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 215.2707 = 14:21:4.97 Dec (J2000.0): -69.4918 = -69:29:30.3 Error: 8.2 arcsec (radius, 90% conf.) Count-rate: (5.1 +/- 1.5)e-3 ct s^-1 Flux: (2.07 +/- 0.62)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020549. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18238 SUBJECT: GRB 150902A: Swift/UVOT Upper Limits DATE: 15/09/04 15:37:25 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and L. Hagen (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150902A 59510 s after the LAT trigger (Arimoto et al., GCN Circ. 18228). No optical afterglow consistent with the XRT Source 1 position given in McCauley et al. (GCN Circ. 18237) is detected in the initial UVOT exposures. Source 2 is outside the UVOT field of view. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures for source 1 are: Filter T_start(s) T_stop(s) Exp(s) Mag white 60331 60972 631 >21.7 v 61152 61997 828 >20.3 u 59510 66787 1184 >20.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.40 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18243 SUBJECT: GRB 150902A: Swift-XRT afterglow detection DATE: 15/09/05 14:09:50 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the Fermi/LAT-detected burst GRB 150902A (Arimoto et al. GCN Circ. 18228). The observations now extend from T0+59.5 ks to T0+192.1 ks. Of the sources reported by McCauley et al. (GCN Circ. 18237), "Source 1" is believed to be the afterglow. The position of this source is RA, Dec=214.9796, -69.3536 which is equivalent to: RA (J2000): 14:19:55.09 Dec(J2000): -69:21:13.1 with an uncertainty of 4.3 arcsec (radius, 90% confidence). This position is 73 arcsec from the Fermi/LAT position. The light curve can be modelled with a power-law decay with a decay index of alpha=1.0 (+0.7, -0.4). The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/ToO_GRBs/00020549/index_1.php. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020549. This circular is an official product of the Swift-XRT team.