//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15099 SUBJECT: GRB 130816B: Swift detection of a burst DATE: 13/08/16 05:06:44 GMT FROM: Michael Stamatikos at OSU/GSFC M. Stamatikos (OSU/NASA/GSFC), P. D'Avanzo (INAF-OAB), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 04:53:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130816B (trigger=566561). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 170.093, -57.558 which is RA(J2000) = 11h 20m 22s Dec(J2000) = -57d 33' 28" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 20 sec. The peak count rate was ~2440 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 04:54:48.8 UT, 70.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 170.01845, -57.55829 which is equivalent to: RA(J2000) = 11h 20m 04.43s Dec(J2000) = -57d 33' 29.8" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 143 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. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 4.04 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 75 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected. Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 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: 15102 SUBJECT: GRB 130816B: Enhanced Swift-XRT position DATE: 13/08/16 12:58:00 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1915 s of XRT Photon Counting mode data and 2 UVOT images for GRB 130816B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 170.01621, -57.55740 which is equivalent to: RA (J2000): 11h 20m 3.89s Dec (J2000): -57d 33' 26.7" with an uncertainty of 1.9 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15103 SUBJECT: GRB 130816B: Swift-XRT refined Analysis DATE: 13/08/16 17:06:04 GMT FROM: Phil Evans at U of Leicester B.P. Gompertz (U. Leicester), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and M. Stamatikos report on behalf of the Swift-XRT team: We have analysed 7.7 ks of XRT data for GRB 130816B (Stamatikos et al. GCN Circ. 15099), from 77 s to 24.0 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 15102). The light curve can be modelled with a power-law decay with a decay index of alpha=0.98 (+0.13, -0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+0.5, -0.4). The best-fitting absorption column is 5.3 (+2.8, -1.3) x 10^21 cm^-2, consistent with the Galactic value of 4.0 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.6 x 10^-11 (8.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.3 (+2.8, -1.3) x 10^21 cm^-2 Galactic foreground: 4.0 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.1 (+0.5, -0.4) If the light curve continues to decay with a power-law decay index of 0.98, the count rate at T+24 hours will be 5.8 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x 10^-14 (4.9 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00566561. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15107 SUBJECT: GRB 130816B: GROND afterglow candidate DATE: 13/08/17 08:19:40 GMT FROM: Karla Varela at MPE K. Varela (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 130816B (Stamatikos et al., GCN #15099) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started at 23:12 UT on 16 August 2013, 18.3 hours after the GRB trigger. They were performed at an average seeing of 1.6" and at and average airmass of 2.20. We find a source inside the 1.9" Swift-XRT error circle (Osborne et al., GCN #15102) at coordinates RA(J2000.0) = 11:20:03.96 DEC (J200.0) = -57:33:27.1 with an uncertainty of 0.5" in each coordinate. Based on the first 460 sec g'r'i'z and 480 sec JHK exposure, we estimate preliminary magnitudes (all in AB) of g' > 23.5 mag r' = 23.1 +/- 0.2 mag, i' = 22.5 +/- 0.2 mag, z' = 21.6 +/- 0.1 mag, J = 20.5 +/- 0.3 mag, H = 20.5 +/- 0.3 mag, K = 19.9 +/- 0.4 mag, calibrated against GROND zero points (griz) and 2MASS (JHK) and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.56 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15108 SUBJECT: GRB 130816B, Swift-BAT refined analysis DATE: 13/08/17 16:08:14 GMT FROM: Tilan Ukwatta at MSU M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130816B (trigger #566561) (Stamatikos, et al., GCN Circ. 15099). The BAT ground-calculated position is RA, Dec = 170.049, -57.527 deg which is RA(J2000) = 11h 20m 11.8s Dec(J2000) = -57d 31' 37.7" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).The partial coding was 98%. BAT mask-weighted light curve shows a single peak starting from ~T-10 sec peaking around T+0 sec and ending at ~T+4 sec. T90 (15-350 keV) is 10.00 +- 3.61 sec (estimated error including systematics). The time-averaged spectrum from T-6.50 to T+6.50 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.45 +- 0.93, and Epeak of 47.3 +- 10.8 keV (chi squared 35.98 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.7 +- 0.4 x 10^-07 erg/cm2 and the 1-sec peak flux measured from T+0.50 sec in the 15-150 keV band is 0.9 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.82 +- 0.17 (chi squared 44.98 for 57 d.o.f.). 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/566561/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 15110 SUBJECT: GRB 130816B: Swift/UVOT Upper Limits DATE: 13/08/19 19:48:10 GMT FROM: Stephen Holland at STScI S. T. Holland (STScI) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130816B starting 75 s after the BAT trigger (Stamatikos et al. 2013, GCNC 15099). We do not detect any new source consistent with the GROND afterglow position (Varela et al. 2013, GCNC 15107) in any of the UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the finding chart (FC) exposures and initial summed exposures are presented below. --------------------------------------------------- Filter TSTART TSTOP Exposure Mag --------------------------------------------------- white (FC) 75 225 147 >20.7 u (FC) 287 537 246 >19.9 --------------------------------------------------- v 618 12,639 1295 >20.4 b 543 7299 530 >20.7 u 692 19,298 923 >20.5 uvw1 667 18,676 1238 >20.8 uvm2 642 13,534 1227 >20.8 uvw2 593 24,128 882 >20.7 white 567 7498 672 >21.5 --------------------------------------------------- The quoted upper limits have not been corrected for the expected extinction due to the Galactic reddening along the line of sight to this burst of E(B-V) = 0.50 mag (Schlafly et al. 2011, ApJS, 737, 103). GRB 130816B was 3 degrees above the Galactic Plane, so this extinction value is highly uncertain.