//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27634 SUBJECT: GRB 200424A: a long GRB detected by INTEGRAL DATE: 20/04/24 12:56:06 GMT FROM: Sandro Mereghetti at IASF-Milano/INAF S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC, Versoix), and J.Borkowski (CAMK, Torun) report: A long gamma ray burst lasting at least 70 s has been detected by IBAS in the IBIS/ISGRI data at 12:07:10 UT of April 24, 2020 The refined coordinates (J2000) are: R.A. = 307.5057 deg DEC. = -39.6939 deg with an uncertainty of 1.5 arcmin (90% c.l.). The burst light curve is affected by telemetry saturation due to the burst brightness. Therefore we can provide only a lower limit on its 20-200 keV fluence of 3e-6 erg/cm2 over a 70 s integration time. A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27636 SUBJECT: GRB 200424A: Swift ToO observations DATE: 20/04/24 15:48:43 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 200424A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00020989 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: 27637 SUBJECT: GRB 200424A: LCO Optical Upper Limit DATE: 20/04/24 20:24:56 GMT FROM: Robert Strausbaugh at U. of the Virgin Islands R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration: We observed INTEGRAL GRB 200424A (Mereghetti et al., GCN 27634) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 24, from 18:48 to 19:23 UT (corresponding to 6.68 to 7.27 hours from the GRB trigger time) with the Bessel I and R filters. We performed a series of 5x240s exposures in R and 4x240s in I. We do not detect any fading sources in the individual frames (or in stacked images). Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits: R > 24.83 I > 22.93 These magnitudes are not corrected for galactic extinction. R.S. is funded by NSF AST grant #1831682 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27640 SUBJECT: GRB 200424A: Swift-XRT observations DATE: 20/04/25 11:11:26 GMT FROM: Paolo D'Avanzo at INAF - OAB M. Perri (ASDC), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (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 200424A (Mereghetti et al. GCN Circ. 27634), collecting 5.0 ks of Photon Counting (PC) mode data between T0+13.2 ks and T0+30.7 ks. One uncatalogued X-ray source has been detected consistent with being within the INTEGRAL position, however it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 307.5055 = 20:30:01.31 Dec (J2000.0): -39.7001 = -39:42:00.5 Error: 3.0 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: (8.3 [+1.7, -1.6])e-3 ct s^-1 Distance: 22 arcsec from INTEGRAL position. Flux: (2.68 [+0.55, -0.52])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Seven uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00020989. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27642 SUBJECT: GRB 200424A: AstroSat CZTI detection DATE: 20/04/25 11:54:17 GMT FROM: Soumya Gupta at IUCAA/ASTROSAT S. Gupta, 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 long GRB 200424A, which was also detected by INTEGRAL (Mereghetti S. et al., GCN #27634), Swift(Evans P. et al., GCN #27636) and LCO (Strausbaugh R. et al., GCN #27637). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 2020-04-24 12:07:18.525 UT. The measured peak count rate associated with the burst is 232 +/- 28 cts/s above the background in the combined data of four quadrants, with a total of 1849 +/- 44 cts. The local mean background count rate was 596 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 43.3 +/- 0.02 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27648 SUBJECT: GRB 200424A: Swift/UVOT Upper Limits DATE: 20/04/25 23:20:23 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the INTEGRAL GRB 200424A (Mereghetti et al. GCN Circ. 27634) between T0+17 ks and T0+31 ks, where T0 = 2020-04-24 12:06:45 UT. We report here the UOT results for source #1 found by the Swift/XRT (D'Avanzo et al., GCN Circ. 27640). 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(ks) T_stop(ks) Exp(s) Mag v 18 30 236 >19.1 b 17 30 236 >20.2 u 17 30 236 >19.9 w1 17 30 492 >19.9 m2 17 31 2678 >20.8 w2 17 30 944 >20.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27676 SUBJECT: GRB 200424A: Swift-XRT afterglow detection DATE: 20/05/02 08:48:04 GMT FROM: Paolo D'Avanzo at INAF - OAB M. Perri (ASDC), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) 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 INTEGRAL-detected burst GRB 200424A (Mereghetti et al. GCN Circ. 27634). The observations now extend from T0+17.1 ks to T0+633.1 ks. Of the sources reported by Perri et al. (GCN Circ. 27640), "Source 1" is fading with 3-sigma significance, and is therefore likely the GRB afterglow. Using 1970 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 307.50547, -39.70013 which is equivalent to: RA (J2000): 20h 30m 01.31s Dec(J2000): -39d 42' 00.5" with an uncertainty of 3.0 arcsec (radius, 90% confidence). This position is 22 arcsec from the INTEGRAL position. The source is fading with alpha >0.3. The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00020989/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00020989. This circular is an official product of the Swift-XRT team.