//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19335 SUBJECT: GRB 160424A: Swift detection of a burst DATE: 16/04/24 11:58:50 GMT FROM: David Palmer at LANL A. Y. Lien (GSFC/UMBC), A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 11:49:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160424A (trigger=683906). Swift did not immediately slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 319.481, -60.405 which is RA(J2000) = 21h 17m 55s Dec(J2000) = -60d 24' 18" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 5 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+48.7 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT 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: 19336 SUBJECT: GRB 160424A: Swift-XRT observations DATE: 16/04/24 13:09:41 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), M. Perri (ASDC) and G. Tagliaferri (INAF-OAB) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 160424A at 12:40:02.1 UT, 3054.8 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 319.48505, -60.41481 which is equivalent to: RA(J2000) = 21h 17m 56.41s Dec(J2000) = -60d 24' 53.3" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 36 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 in excess of the Galactic value (3.94 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.5 (+2.04/-1.82) x 10^21 cm^-2 (90% confidence). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19337 SUBJECT: GRB 160424A: Swift/UVOT Upper Limit DATE: 16/04/24 14:06:06 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and A. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team: UVOT took a finding chart exposure of 150 seconds with the White filter starting 3059 seconds after the BAT trigger (Lien et al. GCN Circ. 19335). No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error region (Evans et al. GCN Circ 19336). Sensitivity is less than usual because of reduced pointing stability. We estimate an upper limit of 16th mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19338 SUBJECT: GRB 160424A: Swift-BAT refined analysis DATE: 16/04/24 20:17:34 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-61 to T+243 sec from the recent telemetry downlinks, we report further analysis of BAT GRB 160424A (trigger #683906) (Lien, et al., GCN Circ. 19335). The BAT ground-calculated position is RA, Dec = 319.482, -60.408 deg, which is RA(J2000) = 21h 17m 55.7s Dec(J2000) = -60d 24' 29.8" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 33%. The mask-weighted light curve shows a FRED-like peak starting at ~T-0.5 sec, peaking at ~T+0.4 sec, and ending at ~T+10 sec. T90 (15-350 keV) is 6.3 +- 1.0 sec (estimated error including systematics). The time-averaged spectrum from T-1.51 to T+6.63 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.40 +- 0.10. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 5.1 +- 0.4 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/683906/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19339 SUBJECT: GRB 160424A - XRT position uncertain DATE: 16/04/25 07:49:42 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: During the XRT observations of GRB 160424A (Evans et al., GCN Circ. 19336) the star trackers onboard Swift were unable to acquire a correct lock. As a result of this the attitude solution for the spacecraft is uncertain, and visual inspection of the images shows that the position of the XRT afterglow is highly uncertain. Our best estimate of the position is as given in GCN Circ. 19336, however the uncertainty is ~50 arc sec. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19340 SUBJECT: GRB 160424A: Fermi GBM observation DATE: 16/04/25 14:58:14 GMT FROM: Hoi-Fung Yu at MPE Hoi-Fung Yu (MPE) reports on behalf of the Fermi GBM Team: "At 11:49:06.48 UT on 24 April 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160424A (trigger 483191350 / 160424492), which was also detected by the Swift (Lien et al. 2016, GCN 19335) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 18 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve shows a single pulse with a duration (T90) of about 7.6 s (50-300 keV). The time-averaged spectrum from T0+0.003 s to T0+6.528 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 220 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (2.6 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+0.832 s in the 10-1000 keV band is 7.2 +/- 0.3 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: 19342 SUBJECT: Konus-Wind observation of GRB 160424A DATE: 16/04/25 16:57:26 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 160424A (Swift-BAT trigger #683906: Lien et al., GCN Circ. 19335; Krimm et al., GCN Circ. 19338; Fermi GBM detection: Hoi-Fung Yu, GCN Circ. 19340) triggered Konus-Wind at T0=42546.397 s UT (11:49:06.397). The burst light curve shows a single pulse with a total duration of ~2.3 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/GRB160424_T42546/ As observed by Konus-Wind, the burst had a fluence of 1.59(-0.35,+0.60)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.464 s, of 1.71(-0.62,+0.84)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.24(-0.51,+0.66) and Ep = 133(-40,+134) keV (chi2 = 58/60 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.0 (chi2 = 57/59 dof) All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.