//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5006 SUBJECT: GRB 060427: Swift detection of a burst DATE: 06/04/27 12:06:37 GMT FROM: Scott Barthelmy at NASA/GSFC V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), S. Campana (INAF-OAB), J. R. Cummings (NASA/ORAU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 11:43:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060427 (trigger=207281). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 124.303, +62.617 {08h 17m 13s, +62d 37' 02"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This was an image trigger so the TDRSS lightcurve does not show any significant activity. The XRT began observing the field at 11:45:20 UT, 130 seconds after the BAT trigger. XRT found a fading, uncatalogued X-ray source located at RA(J2000) = 08h 17m 04.5s, Dec(J2000) = +62d 40' 17.4", with an estimated uncertainty of 5.4 arcseconds (90% confidence radius). This location is 204 arcseconds from the BAT on-board position, outside the BAT error circle. The initial flux in the 2.5s image was 9.6e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 400 seconds with the V filter starting 133 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources has an upper limit of 19.2 mag. No correction has been made for the expected extinction of about 0.2 magnitudes. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5007 SUBJECT: GRB 060427, optical observation DATE: 06/04/27 14:23:05 GMT FROM: Shouta Maeno at U.of Miyazaki S.Maeno, E.Sonoda, M.Yamauchi (University of Miyazaki) "We have observed the field covering the error circle of GRB060427 (GCN 5006) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 11:44:48 UT on Apr.27(98sec after the Swift trigger). After co-adding a set of 13 images (11:44:48 - 12:00:21 UT) of 30 sec exposures, we have compared with the USNO A2.0 catalog. Preliminary analysis shows there is no new source brighter than 15.1 mag." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5010 SUBJECT: GRB060427: Swift XRT Team refined analysis DATE: 06/04/27 17:55:36 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano (INAF-IASFPA), G. Tagliaferri (INAF-OAB), D. N. Burrows (PSU) report on behalf of the Swift XRT Team: We have analyzed the first orbit data of GRB060417 (Mangano et al 2006, GCN 5006). The XRT data set consists of 88 s exposure in Windowed Timing (WT) mode followed by 843 s exposure in Photon Counting (PC) mode. The refined position of the source is RA (2000) = 08h 17m 04.4s Dec (2000) = +62d 40' 18.3" with an uncertainty of 3.4 arcsec (90% confinement). This position is only 1 arcsec from the onboard detected position (Mangano et al 2006, GCN 5006). The 0.2-10 keV X-ray light curve shows an initial very fast decay with slope -4.3 +/- 0.2, a break at 247 +/- 12 s from the trigger and a final decay slope of -1.7 +/- 0.13. The WT and PC spectra were fitted separately with an absorbed power law model and showed photon indices of 2.9 +/- 0.1 and 2.37 +/- 0.14, respectively (90% confidence level). The WT spectrum, covering the time interval 138-227 s, accounts for the pre-break phase of the light curve. Both spectra show evidence of an absorption column at the level of (1.7 +/- 0.2) x 10^21 cm^-2 in excess with respect to the Galactic value of 4.3 x 10^20 cm^-2. The 0.2-10 keV unabsorbed fluxes of the two spectra are 1.3 x 10^-9 and 6.6 x 10^-11 erg cm^-2 s^-1, respectively. If decaying at the present rate the source will reach the flux level of 10^-14 erg cm^-2 s^-1 (corresponding to a count rate level of 1.5 x 10^-4 counts s^-1) after one day. This Circular is an official product of the Swift XRT Team. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5011 SUBJECT: GRB 060427: Refined analysis of the Swift-BAT burst DATE: 06/04/27 21:21:57 GMT FROM: Scott Barthelmy at NASA/GSFC H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), V. Mangano (INAF-IASFPA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 060427 (trigger #207281) (Mangano, et al., GCN 5006). The BAT ground-calculated position is RA,Dec = 124.175,+62.654 deg {8h 16m 42.0s,+62d 39' 13.4"} (J2000) +- 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%. The mask-weighted lightcurve shows a broad peak starting at ~T-20 sec and lasting to ~T+80 sec. T90 (15-350 keV) is 64 +- 5 sec (estimated error including systematics). The time-averaged spectrum from T-10.0 to T+60.0 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.87 +- 0.29. The fluence in the 15-150 keV band is 5.0 +- 0.9 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+5.00 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5012 SUBJECT: GRB 060427: Swift/UVOT upper limits. DATE: 06/04/27 21:25:56 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (UCL-MSSL), V. Mangano (IASF Palermo) report on behalf of the Swift/UVOT team: The Swift/UVOT began taking data on the field of GRB060427 at 11:45:13 UT on 2006-04-27, 122 s after the BAT trigger (Mangano et al., GCN 5006), with the settling exposure. No afterglow candidate was detected at the refined XRT position (Falcone et al., GCN 5009) in summed images from any of the filters down to the following three-sigma upper limits. Filter T_range(s) Exp(s) 3sig_UL V 122-6920 1668 20.4 B 610-6635 416 20.7 U 585-6430 436 20.3 UVW1 562-6226 457 20.0 UVM2 562-6021 456 20.0 UVW2 626-6840 436 20.5 These upper limits are uncorrected for the estimated Galactic reddening of E_{B-V} = 0.051 mag (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5013 SUBJECT: GRB 060427: NOT observations DATE: 06/04/27 22:50:06 GMT FROM: Martin Jelinek at Inst.Astrophys.Andalucia,Granada A. R. López-Sánchez, J. García-Rojas (IAC La Laguna), M. Jelínek and A. J. Castro-Tirado (IAA-CSIC Granada), report on behalf of a larger collaboration: "Following the detection by SWIFT of GRB 060427 (V. Mangano et al. GCNC 5006), we have obtained R & I-band images at the 2.5m Nordic Optical Telescope (+ ALFOSC), starting on Apr 27.876 UT (i.e. 9.25 hr after the onset of the event). At the position of the X-ray afterglow detected by SWIFT/XRT (V. Mangano et al. GCNC 5010), no optical source is detected in the 600s R-band image, down to a limiting magnitude of R = 23.5." This message can be quoted. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5015 SUBJECT: GRB060427: Xinglong optical Observations DATE: 06/04/28 05:29:04 GMT FROM: W.K. Zheng at NAOC M.Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng and W.K. Zheng, report on behalf of EAFON: We have observed the field of GRB060427 (GCN 5006) with the Xinglong 0.8m telescope 4.788 hours after the burst, thers is no new source brighter than 18.7(3-sigma) Mag within 4x600s combined R-band image. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5016 SUBJECT: GRB 060427: NIR observations DATE: 06/04/28 07:49:36 GMT FROM: Paul Price at IfA,UH P.A. Price (IfA, Hawaii), D.B. Fox (Penn State), S.B. Cenko (Caltech), E. Berger (OCIW), B.P. Schmidt (RSAA, ANU) and L.L. Cowie (IfA, Hawaii) report on behalf of a larger collaboration: We have observed the XRT localisation of the afterglow of GRB 060427 (GCN #5010) with the Gemini North telescope + NIRI under variable clouds. Our observations commenced at 2006 Apr 28.23 UTC, and consisted in 18 x 60 sec exposures in J-band. Visual inspection of the combined J-band image does not reveal any afterglow candidate at the XRT position to a limiting magnitude of J ~ 20.5 mag, based on three 2MASS sources in the field. Additional H-band exposures have not yet been examined. The afterglow is therefore likely faint, rather than at high redshift. We thank Tom Matheson and the Gemini North observing team for performing these ToO observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5020 SUBJECT: GRB060427:MASTER optical limit DATE: 06/04/28 13:03:32 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, A.Belinski, E.Gorbovskoy, A.Krylov, G.Borisov, A.Sankovich, N.Shatskiy, V.Vladimirov S.Korobkin, P.Gritsyk Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB060427.4 (GRB_TIME is 2006-04-27 09:04:33.53, V. Mangano, S. D. Barthelmy et al.(GCN5006). The first image was at 2006-04-27 18:18:07 UT, 09:13:33.47 after the GRB time The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). The robot not find OT-candidate in error box (V. Mangano et al. GCN5010) brighter then 17.5 (s/n=3). This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5030 SUBJECT: GRB 060427B: IPN localization of a short hard burst DATE: 06/04/28 18:55:15 GMT FROM: Kevin Hurley at UCBerkeley/SSL S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, and D. Frederiks on behalf of the Konus-Wind team, K. Hurley and T. Cline on behalf of the Ulysses, Mars Odyssey, and Konus GRB teams, I. Mitrofanov, A. Kozyrev, M. Litvak, A. Sanin, V. Tret'yakov and A. Parshukov, on behalf of the HEND-Odyssey GRB team, W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS-Odyssey GRB team, S. Barthelmy, J. Cummings, N. Gehrels, and H. Krimm, on behalf of the Swift-BAT team, and A. von Kienlin, G. Lichti, A. Rau, D. Gotz, and S. Mereghetti, on behalf of the INTEGRAL GRB team, report: A short duration hard spectrum GRB, 060427B, occurred at about 23:51:55 UT. It was observed by Konus-Wind, Mars Odyssey (GRS and HEND), INTEGRAL-SPI-ACS, and Swift-BAT. The burst was outside of the field of view of Swift-BAT, so it was not imaged. As the burst arrived almost along the Odyssey-Earth vector, the resulting annulus was unusually wide. The burst light curve shows a single pulse with a duration of ~0.2 sec. A weak emission is seen in the K-W G2 band (83-360 keV) starting at ~0.3 sec before the main pulse. The burst has been triangulated to RA, Dec = 98.472, +21.348 deg (J2000). The corners of the 3 sigma error box are: ----------------------- RA, deg Dec, deg ----------------------- 98.8479 22.7146 98.7014 19.9202 98.0629 19.9948 98.1954 22.8568 -------------------- The area of this error box is 1.7 sq. deg. Konus-Wind spectral analysis is in progress. Preliminary analysis indicates that Epeak was >1 MeV. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5032 SUBJECT: GRB 060427B: MASTER optical observations DATE: 06/04/28 21:15:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, N.Tyurina, A.Belinski, D.Kuvshinov, E.Gorbovskoy, A.Krylov, N.Shatskiy, G.Borisov, A.Sankovich, V.Vladimirov, P.Gritsyk, S.Korobkin Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) observed GRB060427B error box (GRB_TIME is 2006-04-27 23:51:55 UT, IPN triangulation, S. Golenetskii et al. GCN5030) in survey mode at considerable zenit distances. The weather was good. We start at 28 apr 2006 18:27:10.44 (18.5 h after the GRB time) and now we have more than 20 images (each 6 square degrees) of the large error box. We note that the error box is very close to galactic plane and we have a lot of objects. The reduction is continued. MASTER team thanks to Konus team for collaboration. This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5038 SUBJECT: Konus-Wind observation of GRB 060427B DATE: 06/04/30 14:04:51 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The short hard GRB 060427B localized by IPN (Golenetskii et al., GCN 5030) triggered Konus-Wind at T0=85912.029 s UT (23:51:52.029). As observed by Konus-Wind it had the fluence 4.95(-3.53,+0.71)x10^-6 erg/cm2, and the 16-ms peak flux measured from T0-0.012 s 4.30(-3.27, +1.27)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The spectrum of the burst integrated from T0 to T0+0.128 s is well fitted (in the 20 keV - 10 MeV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep) with alpha = 0.573 (-0.404, +0.284) and Ep = 1746 (-582, +962) keV (chi2 = 24.5/22 dof). All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5061 SUBJECT: GRB 060427B Milagro GeV/TeV Observations DATE: 06/05/03 00:01:46 GMT FROM: Pablo Saz Parkinson at UCSC/Milagro Pablo Saz Parkinson (UC Santa Cruz) on behalf of the Milagro collaboration reports: We have searched Milagro data for emission at GeV/TeV energies from GRB 060427B (GCN Circ 5030, K. Hurley et al.), during the burst duration (0.2 s) reported by the IPN team. No evidence for prompt GeV/TeV emission was found. A preliminary analysis, assuming a differential photon spectral index of -2.4, gives an upper limit on E^2dN/dE at 99% confidence of: E^2dN/dE at 2 TeV < 4.8 * 10^(-8) erg cm^(-2) (No EBL absorption) TeV photons are attenuated by pair production with infrared photons in intergalactic space. We calculate an upper limit assuming a redshift of 0.5 (a value representative of short/hard bursts) using the extragalactic infrared background light (EBL) absorption model of Primack et al. 2005 (AIP Conf. Proc. 745, p. 23). We find 99% confidence level upper limits on E^2dN/dE of: E^2dN/dE at 150 GeV < 5.1 * 10^(-6) erg cm^(-2) (Primack et al. EBL model) The energies quoted represent the approximate median energy of the events that would be detected assuming a power law spectrum with differential index -2.4 convolved with the absorption model. These upper limits are preliminary and will be refined with further analysis.