//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18623 SUBJECT: GRB 151120A: A long GRB detected by INTEGRAL DATE: 15/11/20 09:23:58 GMT FROM: Sandro Mereghetti at IASF/CNR S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, Godze Saral (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: a gamma ray burst lasting about 50 s has been detected by IBAS in the IBIS/ISGRI data at 8:22:50 UT of 2015 November 20. The refined coordinates (J2000) are: R.A.= 157.2502 deg DEC.= -32.5237 deg with an uncertainty of 1.5 arcmin (90% c.l.). The burst saturated the available ISGRI telemetry, therefore we can only provide a lower limit for the fluence in the 20-200 keV energy range of 2e-6 erg/cmq. A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18624 SUBJECT: GRB 151120A: GROND optical/NIR afterglow DATE: 15/11/20 09:58:39 GMT FROM: Thomas Kruehler at MPE Garching T. Kruehler, J. Greiner, J. Ridl (all MPE) and A. Hempel (Universidad Andres Bello) report on behalf of a larger collaboration: We observed the field of GRB 151120A (INTEGRAL trigger 7295; Mereghetti et al., GCN #18623) simultaneously in grizJHK 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 November 20, 2015, 08:27 UTC, 4 minutes after the GRB trigger. They were performed at an average seeing of 1.3" and at an average airmass of 1.2. Inside the INTEGRAL error circle (Mereghetti et al., GCN #18623), we detect an uncatalogued and variable source, which we consider the optical/NIR afterglow of GRB 151120A. The object is at: RA (J2000): 10:28:57.94 Dec (J2000): -32:31:35.1 with an estimated uncertainty of 0.5" in each coordinate. Based on 4.4 min of total exposures in griz and 4 min in JHK obtained at a midtime of 15 minutes after the trigger, we derive preliminary magnitudes of: g = 20.0 +- 0.1 r = 19.4 +- 0.1 i = 19.0 +- 0.1 z = 18.8 +- 0.1 J = 18.2 +- 0.1 H = 18.0 +- 0.2 K = 18.0 +- 0.3 These measurements are in the AB system and calibrated against GROND zero-points in griz as well as 2MASS field stars in JHK. They are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlafly & Finkbeiner et al. 2011). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18625 SUBJECT: GRB 151120A: Swift ToO observations DATE: 15/11/20 12:43:15 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 INTEGRAL GRB 151120A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020559 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 INTEGRAL 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: 18628 SUBJECT: GRB 151120A: Fermi GBM observation DATE: 15/11/20 15:43:09 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE)reports on behalf of the Fermi GBM Team: "At 08:22:53.70 UT on 20 November 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 151120A (trigger 469700577 / 151120349), which was also detected by the INTEGRAL/ISGRI (Mereghetti et al. 2015, GCN 18623) The GBM on-ground location is consistent with the INTEGRAL position. The angle from the Fermi LAT boresight at the GBM trigger time is 65.6 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+21.760 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.29 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 243 (+23/-19)keV. The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.3)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+11.9682 s in the 10-1000 keV band is 7.0 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 217 (+27/-25) keV, alpha = -1.26 +/- 0.04 and beta = -2.30 (+0.20/-0.40). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18629 SUBJECT: GRB 151120A: Swift-XRT afterglow detection DATE: 15/11/20 20:16:45 GMT FROM: Sarah Gibson at U.of Leicester A.P. Beardmore (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), S.L. Gibson (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the INTEGRAL-detected burst GRB 151120A (Mereghetti et al. GCN Circ. 18623), collecting 3.9 ks of Photon Counting (PC) mode data between T0+16.4 ks and T0+23.6 ks. An uncatalogued X-ray source is detected inside or close to the INTEGRAL error region and is above the RASS limit, and is therefore likely the GRB afterglow. The position of this source is RA, Dec=157.2410, -32.5262 which is equivalent to: RA (J2000): 10:28:57.83 Dec(J2000): -32:31:34.2 with an uncertainty of 3.6 arcsec (radius, 90% confidence). This position is 29 arcsec from the INTEGRAL position and 1.6 arcsec from the afterglow detected by GROND (GCN 18624). The light curve can be modelled with a power-law decay with a decay index of alpha=2.3 (+1.0, -0.9). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.00 (+0.31, -0.28). The best-fitting absorption column is 2.7 (+1.3, -1.1) x 10^21 cm^-2, in excess of the Galactic value of 9.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.7 (+1.3, -1.1) x 10^21 cm^-2 Galactic foreground: 9.0 x 10^20 cm^-2 Excess significance: 2.8 sigma Photon index: 2.00 (+0.31, -0.28) If the light curve continues to decay with a power-law decay index of 2.3, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.5 x 10^-14 (1.1 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/ToO_GRBs/00020559/index_1.php. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020559. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18636 SUBJECT: Konus-Wind observation of GRB 151120A DATE: 15/11/23 10:14:13 GMT FROM: Anna Kozlova 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 GRB 151120A (INTEGRAL ISGRI detection: S. Mereghetti et al., GCN Circ. 18623; Fermi GBM detection: A. von Kienlin, GCN Circ. 18628) triggered Konus-Wind at T0=30171.357 s UT (08:22:51.357). The burst light curve shows a multipeaked structure started at ~T0-1.3 s with a total duration of ~20 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB151120_T30171/ As observed by Konus-Wind, the burst had a fluence of 7.20(-1.25,+1.79)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.752 s, of 2.09(-0.88,+1.15)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.26 (-0.48,+0.77), the high energy photon index beta = -2.70 (-0.88,+0.35), the peak energy 106 (-19,+20) keV (chi2 = 84/85 dof) The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = 0.81 (-0.75,+3.91), the high energy photon index beta = -2.42 (-0.38,+0.35), the peak energy 113 (-40,+22) keV (chi2 = 81/82 dof) All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.