This file contains both bursts: Swift GRB 070724A and SuperAGILE GRB 070724B. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6654 SUBJECT: GRB 070724: Swift detection of a burst DATE: 07/07/24 11:22:00 GMT FROM: Scott Barthelmy at NASA/GSFC H. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), M. De Pasquale (UCL-MSSL), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), P. Romano (Univ. Bicocca & INAF-OAB), B. Sbarufatti (INAF-IASFPA), P. Schady (MSSL-UCL), M. Stamatikos (NASA/ORAU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 10:53:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070724 (trigger=285948). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 27.818, -18.622 which is RA(J2000) = 01h 51m 16s Dec(J2000) = -18d 37' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a strong spike about one second long at T+0 sec. The peak count rate was ~2700 counts/sec (15-350 keV), at ~0 sec after the trigger. This could be a short burst although the spectrum is not hard. The XRT began observing the field at 10:54:56 UT, 67 seconds after the BAT trigger. Using prompt downlinked data, we find a variable, uncatalogued X-ray source located at RA, Dec 27.8077, -18.5951 which is RA(J2000) = 01 51 13.86 Dec(J2000) = -18 35 42.4 with an uncertainty of 4.7 arcsec (radius, 90% containment). This location is 102 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 6.4e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100s with the White filter starting 75s 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 3-sigma upper limit is about 19.2 mag. No correction has been made for the expected reddening of E(B-V) of 0.01. Burst Advocate for this burst is H. Ziaeepour (hz AT mssl.ucl.ac.uk). 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: 6656 SUBJECT: GRB 070724, Swift-BAT refined analysis of a short burst DATE: 07/07/24 15:31:04 GMT FROM: Ann M. Parsons at NASA/GSFC/Swift A. Parsons (GSFC), L. Barbier (GSFC), S.D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU), H. Ziaeepour (UCL-MSSL) (i.e. the Swift-BAT team): Using the data set from T-310 to T+ 310 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070724 (trigger #285948) (Ziaeepour, et al., GCN Circ. 6654). The BAT ground-calculated position is RA, Dec = 27.824, -18.610 deg which is RA(J2000) = 1h 51m 17.9s Dec(J2000) = -18d 36' 35" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%. The mask-weighted light curve for GRB 070724 consists of a single spike peaking at T+0.2 sec. Upon inspection of the mask weighted light curve out to T + 310 sec we find no evidence for extended emission. T90 (15-350 keV) is 0.4 +- 0.04 sec (estimated error including systematics). The time-averaged spectrum from T-0.0 to T+0.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.81 +- 0.33. The fluence in the 15-150 keV band is 3.0 +- 0.7 x 10^-08 erg/cm2. The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6658 SUBJECT: GRB 070724: Pre-Imaging Shows a Source in the XRT Error Circle DATE: 07/07/24 17:03:08 GMT FROM: Josh Bloom at UC Berkeley J. S. Bloom (UC Berkeley) notes: "The JFN color plates from the Digitized Sky Survey show a blue source in the Northeast portion of the XRT error circle of SHB 070724 (Ziaeepour et al. GCN 6654; Parsons et al. GCN 6656) at position RA= 01:51:14.05, DEC = -18:35:39.1 (J2000). The source appears somewhat extended in the north-south direction; if confirmed with new digital imaging, this would suggest the source as a prime low redshift star-forming host galaxy candidate." An image may be found at: http://lyra.berkeley.edu/~jbloom/grb070724.png No need to cite this message. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6659 SUBJECT: GRB 070724: Swift-XRT Team refined analysis DATE: 07/07/24 17:29:58 GMT FROM: Kim Page at U.of Leicester K.L Page (U. Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift-XRT team: We have analysed the first three orbits of Swift-XRT data obtained for GRB 070724 (Ziaeepour et al., GCN Circ. 6654), which includes ~60 s of Windowed Timing (WT) mode data and ~5.2 ks of Photon Counting (PC) data. Using 399 s of overlapping XRT PC mode and UVOT V-band data, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) of RA, Dec (J2000) = 27.80815, -18.59448 which is equivalent to: RA (J2000): 01 51 13.96 Dec (J2000): -18 35 40.1 with an uncertainty of 2.2 arcsec (radius, 90% confidence). This is 2.7 arcsec from the initial XRT position (GCN Circ. 6654) and 77.8 arcsec from the ground-calculated BAT position (Parsons et al., GCN Circ. 6656). The first orbit of XRT data shows flaring activity, with the underlying power-law decay asserting itself from about 500 seconds after the trigger. This decay slope is poorly constrained with the data currently available: alpha ~ 0.4 +0.3/-0.2 Fitting the PC data from the second and third orbits (~4-12 ks after the trigger) in order to avoid any spectral evolution during the flares, the spectrum can be modelled by a power-law of Gamma = 1.3 +0.8/-0.6, absorbed by the Galactic column in this direction of 1.43e20 cm^-2. The 0.3-10 keV observed (unabsorbed) flux during this time is 5.18e-13 (5.27e-13) erg cm^-2 s^-1. If the decay continues with a slope of alpha ~ 0.4, the count rate at 24 hours is predicted to be 4e-3 count s^-1; this ranges between 2e-3 and 8e-3 count s^-1, taking into account the uncertainties on the slope. Using the spectral fit detailed above, this corresponds to an observed flux of (2 +7/-1)e-13 erg cm^-2 s^-1 (over 0.3-10 keV). This circular is an official product of the XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6660 SUBJECT: Swift/UVOT refined analysis of GRB070724 DATE: 07/07/24 18:05:38 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL-UCL) and H. Ziaeepour (MSSL-UCL) report on the behalf of the Swift UVOT/team: The Swift/UVOT observed the field of GRB070724 starting 58s after the BAT trigger (Ziaaepour et al. GCN circ. 6654). Inside the refined XRT error circle (Page et al., GCN circ 6659) we do not find any new source, either in the first finding chart exposures in the White and V filter or in the summed exposures of any of the UVOT filters. The 3 sigma upper limits for detecting a source inside the XRT error circle are: Filter T obs (s) Exp (s) Mag (3 sigma u.l.) White 76-176 98 20.4 v 182-581 393 19.5 White 76-5531 380 21.1 v 182-5941 806 20.0 b 662-5325 216 20.3 u 636-6456 332 20.0 uvw1 612-6352 432 20.4 uvm2 587-6146 432 20.4 uvw2 692-5736 432 20.7 No correction has been done for the expected low Galactic reddening towards the burst, E(B-V)=0.01 (Schlegel et al. 11998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6661 SUBJECT: GRB 070724: Closer association with DSS source DATE: 07/07/24 19:07:24 GMT FROM: Josh Bloom at UC Berkeley J. S. Bloom and N. R. Butler (UC Berkeley) remark: "The updated XRT position of GRB 070724 from Page & Ziaeepour (GCN #6659), puts the GRB afterglow closer to the proposed low redshift host (Bloom GCN #6658) seen in the DSS. We emphasize that the galaxy nature of this source has yet to be confirmed; yet, the small offset (<~ 2") is reminiscent of the SHB 050709 (Fox et al. Nature, 437, 845, 2005) and SHB 051221 (Soderberg et al. ApJ, 650, 261, 2006) configurations (see Bloom & Prochaska for an early SHB-host offsets review; AIP Conf. Proc. 838, 473, 2006)." An updated finder can now be found at: http://lyra.berkeley.edu/~jbloom/grb070724-update1.png We thank Massimiliano de Pasquale for helpful conversations about the UVOT imaging. This message could, in principle, be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6662 SUBJECT: GRB 070724: IR observations DATE: 07/07/24 20:50:02 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (Warwick), N.R. Tanvir (Leicester), C. Davis (JAC) report on behalf of a large collaboration: We observed the location of GRB 070724 in the K-band using UKIRT. Two epochs were obtained beginning at 13:11 UT and 14:02 UT. We clearly detect the object refered to by (Bloom GCNC 6658), and confirm that it is indeed a galaxy. We find no evidence of variability within the galaxy between the two observations. No other objects are detected within the refined XRT error circles of Page & Ziaeepour (GCNC 6659) or Bloom & Butler (GCNC 6661). Further observations are planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6664 SUBJECT: GRB 070724: P60 and Gemini Observations DATE: 07/07/25 07:28:40 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko, A. Rau (Caltech), E. Berger (Carnegie/Princeton), P. A. Price (IfA), and A. Cucchiara (Penn State) report on behalf of a larger collaboration: We have imaged the field of GRB070724 (Ziaeepour et al., GCN 6654) on the night of 2007 July 24 UT with the automated Palomar 60-inch telescope (beginning approximately 2.5 minutes after the burst) and the Gemini Multi-Object Spectrograph (GMOS) and Near-Infrared Imager (NIRI) mounted on the 10-m Gemini North Telescope (beginning approximately 2 hours after the burst). The nearby galaxy first mentioned by Bloom (GCN 6658) shows no sign of variability, either from our P60 to our GMOS imaging (remaining at a constant magnitude of i' ~ 20.3), or within our Gemini imaging (verified with psf-matched digital image subtraction). In addition the aforementioned galaxy, we find a faint source on the outskirts of the revised XRT error circle (Page and Ziaeepour, GCN 6659) at coordinates (J2000.0): RA: 01:51:14.05 Dec: -18:35:42.1 with an estimated astrometric uncertainty of approximately 0.3" in each coordinate. The object is only visible in our Gemini/GMOS i' imaging of the field, with a magnitude of i' ~ 24.6 (using GMOS zeropoints from the Gemini webpage). This object is not present in our earlier P60 imaging of the field; however it is well below our detection threshold (see below). As our only two Gemini/GMOS i' images were taken back-to-back, we have no information on the variability of this source at the current time. No other object is detected in the revised XRT error circle in any other filter. Our limiting magnitudes, calculated with respect to the USNO-B catalog (P60) or using zeropoints from the Gemini website (GMOS and NIRI), are quoted below: Instrument Filter UT (July 24) dt (hr) Exposure (s) Magnitude --------------------------------------------------------------------------- P60 i' 11:13 0.32 3x60 + 3x120 > 21.5 GMOS i' 13:17 2.38 2x180 > 24.5 NIRI Ks 13:44 2.83 15x60 > 20.0 NIRI J 14:02 3.13 15x60 > 22.0 NIRI H 14:19 3.42 15x60 > 21.0 NIRI Ks 14:36 3.70 15x60 > 20.0 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6665 SUBJECT: GRB070724: Host galaxy redshift DATE: 07/07/25 10:23:16 GMT FROM: Antonino Cucchiara at PSU A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko (Caltech), E. Berger (Carnegie), P. A. Price (IfA) and J. Radomski (Gemini) report on behalf of a larger collaboration: Starting on 2007 July 25 at 06:40 UT we used GMOS on the Gemini South telescope to obtain a set of 900 seconds spectra of the host galaxy of GRB070724 (Ziaeepour et al., GCN 6654). The covered wavelength range is ~5000-9000 A. We found strong evidence of emission lines identified as [O II] 3727, Hbeta and [O III] 4959,5007 doublet at redshift z=0.457. This confirms the low-redshift nature of the host galaxy for this short burst as noted by Bloom et al. (GCN 6658). We wish to thank and acknowledge the effort of the staff at Gemini South in undertaking these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6666 SUBJECT: GRB 070724: optical observations DATE: 07/07/25 13:21:12 GMT FROM: Silvia Piranomonte at OAR S. Covino (INAF/OABr), S. Piranomonte (INAF/OAR), S.D. Vergani (DIAS and DCU), P. D'Avanzo (INAF-OABr), L. Stella (INAF/OAR), report on behalf of the MISTICI collaboration: We observed the afterglow of GRB 070724 (Ziaeepour et al., GCN 6654) with the ESO-VLT equipped with FORS2. Starting on 2007 Jul 25.3735 UT (22.1 hr after the trigger), we acquired 10 minutes of imaging in the I band. Inside the XRT error circle (Page & Ziaeepour, GCN 6659), we detect both objects reported by Bloom (GCN 6658) and Cenko et al. (GCN 6664). When compared with the photometry reported by Cenko et al. (GCN 6664), none of the objects seems to have faded. The faintest object is pointlike (seeing of 0.7"). We also took two 10-min spectra with VLT+FORS2. Based on detection of [OII] 3727 Hbeta and [OIII] 4959,5007, we confirm the redshift z=0.457 proposed by Cucchiara et al. (GCN 6665). We thank Brad Cenko for very useful discussion. ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6667 SUBJECT: Four radio sources in Swift-XRT error box of GRB 070724 DATE: 07/07/25 18:21:35 GMT FROM: Poonam Chandra at U Virginia/NRAO Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We used the Very Large Array to observe the field of view toward GRB 070724 (GCN 6654) at a frequency of 8.46 GHz on 2007 July 25th at 12.50 UT, 25.4 hours after the burst. Owing to VLA A-array observation, we obtained excellent resolution of 0.33"x0.24". We find four possible sources in the Swift-XRT error box, which are above 3-sigma. These are Position (J2000) Flux density (Jy) 1: RA 01 51 14.105 +/- 0.002 4.3899E-04 +/- 8.40E-05 DEC -18 35 45.938 +/- 0.024 2: RA 01 51 14.125 +/- 0.002 4.0976E-04 +/- 8.51E-05 DEC -18 35 41.404 +/- 0.021 3: RA 01 51 13.824 +/- 0.003 3.1155E-04 +/- 8.48E-05 DEC -18 35 36.626 +/- 0.033 4: RA 01 51 14.104 +/- 0.003 3.1204E-04 +/- 8.47E-05 DEC -18 35 40.626 +/- 0.030 Here source 4 is closest to Josh Bloom's blue source (GCN 6658) with offset of 1.7 arcsec. Source 2 is closest to P60 afterglow position of the GRB (Cenko et al. GCN 6664) with offset of 1.3 arcsec. NVSS does not show any radio source around this position. More observations are planned to see the variability of these sources. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6668 SUBJECT: GRB 070724b: First Gamma Ray Burst Localization by SuperAGILE onboard DATE: 07/07/25 18:29:51 GMT FROM: Marco Feroci at IASF/INAF GRB 070724b: First Gamma Ray Burst Localization by SuperAGILE onboard AGILE M. Feroci, E. Costa, E. Del Monte, I. Donnarumma, Y. Evangelista, I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda, P. Soffitta, A. Rubini, E. Morelli, M. Mastropietro, G. Di Persio, M. Frutti, and S. Mereghetti, A. Pellizzoni, G. Di Cocco, C. Labanti, M. Trifoglio, G. Barbiellini, P. Picozza, A. Argan and M. Tavani, on behalf of the AGILE Team, P. Giommi, L.A. Antonelli, C. Pittori (ASDC), and L. Salotti (ASI) report: The SuperAGILE experiment onboard the AGILE mission, launched on April 23rd on an equatorial orbit, is currently performing the in-flight check-out and performance verification. The experiment is not yet in its optimal configuration and not all the functions are active. In particular, the onboard triggering and imaging is not active yet and the absolute position reconstruction is being calibrated by using celestial X-ray sources. During this testing phase SuperAGILE detected and imaged GRB 070724b. The event starting time is approximately at 23:25:09 UT on July 24 and it was observed at 21 degrees off-axis. The observed duration in the 20-60 keV energy range is about 55 seconds, with a multi-peak time structure. The burst position was reconstructed as (RA, Dec) (17.629 deg, 57.673 deg), which is: RA(J2000) = 01h 10m 31.0s Dec(J2000) = +57d 40' 23" with an uncertainty of 20' radius. The given uncertainty is almost entirely systematic and it is due to the very preliminary absolute position calibration, carried out only on 3 X-ray sources. At this preliminary stage the absolute positioning was obtained by the ground calibrations, preliminarily checked with these sources. The error box may be improved over the next hours/days. An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress. A quick look analysis does not show any bright gamma-ray transient in coincidence with the X-ray emission of GRB 070724b. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6669 SUBJECT: GRB 070724B: Swift-XRT afterglow candidates DATE: 07/07/25 23:50:43 GMT FROM: Pat Romano at OAB-Swift P. Romano(Uni-Bicocca and OAB), J.A. Kennea(PSU), C. Guidorzi(Uni-Bicocca and OAB), D. Burrows(PSU) report on behalf of the Swift-XRT team: We have analysed the first two orbits of Swift-XRT data obtained for GRB 070724B detected by SuperAGILE (Feroci et al., GCN Circ. 6668), which include 3971s of Photon Counting (PC) mode data, beginning on 2007-07-25 18:32:39 UT, 19.1 hours after the burst trigger time. Using the PC data we found two sources within the SuperAGILE error circle, at the following positions: 1) RA, Dec=17.48574, 57.67613, which is equivalent to RA(J2000) = 01 09 56.58 Dec(J2000) = +57 40 34.1 with an estimated error radius of 4.5 arcsec (90% confidence). This position lies 4.6 arcmin from the SuperAGILE position (GCN Circ. 6668). The current observed 0.3-10 keV count rate is (3.9+/-0.4)E-02 counts/s, which translates into a 0.3-10 keV flux of ~2E-12 erg/cm2/s (assuming a power-law with photon index=2 absorbed by a column of NH=E21 cm-2). 2) RA, Dec= 17.51024, 57.81898, which is RA(J2000) = 01 10 02.46 Dec(J2000) = +57 49 08.3 with an estimated error radius of 6.1 arcsec (90% confidence). This position lies 9.5 arcmin from the SuperAGILE position. The current observed 0.3-10 keV count rate is (0.6+/-0.2)E-02 counts/s, which translates into a 0.3-10 keV flux of ~3E-13 erg/cm2/s. More data are being collected and a new circular will be issued when the fading nature of these objects is established. This circular is an official product of the XRT team. [GCN OPS NOTE(26jul07): Per author's request, DB's affiliation was added, "17.1 hours" was changed to "19.1 hours", and the exponent of the count rate in the second source changed from "03" to "02".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6670 SUBJECT: GRB 070724B: Analysis of AGILE gamma-ray data DATE: 07/07/26 15:31:47 GMT FROM: Sandro Mereghetti at IASF/CNR A.Chen, S.Vercellone, A.Giuliani, A.Pellizzoni, F.Fornari, S.Mereghetti, F.Perotti, M.Fiorini, P.Caraveo (IASF-Milano), C.Labanti, M.Marisaldi, F.Fuschino, M.Galli, A.Bulgarelli, F.Gianotti, M.Trifoglio, G.Di Cocco (IASF-Bologna), M.Tavani, G.Pucella, F.D'Ammando, E.Costa, M.Feroci, A.Trois, A.Argan (IASF-Roma), G.Picozza (INFN-Roma), F.Longo, G.Barbiellini (INFN-Trieste) on behalf of the AGILE Team and C. Pittori, P.Giommi, L.A.Antonelli (ASDC), and L. Salotti (ASI) report: Further analysis of the AGILE GRID (Gamma-Ray Imaging Detector) data of GRB 070724B (Feroci et al. GCN 6668) confirms the absence of significant emission at energy above 50 MeV. Only one photon consistent with the direction of GRB 070724B has been detected by the GRID in a ~100 second interval around the time of the burst. This is consistent with the measured background rate. We note that a gamma-ray flux similar to that observed with EGRET from GRB930131 (Sommer et al.1994, ApJ 422, L66), would have given about 20 counts in the GRID in the same time interval. We also analyzed the data of the AGILE Mini-Calorimeter, which provides a nearly whole-sky monitor in the energy range ~0.35-3 MeV (no directional information), without finding any statistically significant count rate increase in correspondence of GRB 070724B. [GCN OPS NOTE(26jul06): Per author's reuqest, the Subject line was changed from "070734B" to "070724B".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6671 SUBJECT: Konus-Wind observation of GRB 070724B DATE: 07/07/26 15:32:31 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 long soft GRB 070724B localized by SuperAGILE (Feroci et al., GCN 6668), triggered Konus-Wind at T0=84307.346 s UT (23:25:07.346). The Konus-Wind light curve shows the main multipeaked pulse with a total duration of ~50 s followed by a weak pulse at T-T0 ~102 sec with a duration of ~10 s. As observed by Konus-Wind the burst had a fluence of 1.80(-0.25, +0.04)x10^-5 erg/cm2, and a 64-ms peak flux measured from T0+29.744 s 2.17(-0.45, +0.34)x10^-6 erg/cm2/s (both in the 20 - 500 keV energy range). The time-integrated spectrum of the burst (from T0 to T0+49.408 s) can be fitted (in the 20 - 500 keV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep) with alpha = 1.15 +/- 0.13 and Ep = 82 +/- 5 keV (chi2 = 40/42 dof). All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070724_T84307/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6672 SUBJECT: GRB 070724B: Suzaku WAM observation of the prompt emission DATE: 07/07/26 15:56:40 GMT FROM: Kazutaka Yamaoka at Aoyama Gakuin U A. Endo, M. Tashiro, Y. Urata, K. Onda, M. Suzuki, N. Kodaka, K. Morigami (Saitama U.), Y. Terada, T. Tamagawa (RIKEN), M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira (Hiroshima U.), K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.), T. Enoto, R. Miyawaki, K. Nakazawa, K. Makishima (Univ. of Tokyo), E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara (Univ. of Miyazaki), M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report: The long GRB 070724B (Feroci et al., GCN 6668) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 23:25:09 UT (=T0). The observed light curve with 1/64 sec time resolution shows a multi-peaked structure with a duration (T90) of about 41 sec. The fluence in 100-1000 keV was 1.04 (+0.08,-0.07) X10^-5 erg/cm^2. The 1-s peak flux measured from T0+39 sec to T0+40 sec was 3.33 (+/- 0.40) photons/cm^2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-2 sec to T0+43 sec is well fitted by a single power-law with a steep photon index of 2.8 +/- 0.2 (chi^2/d.o.f. = 17.3/21). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6673 SUBJECT: GRB 070724A: further VLT observations DATE: 07/07/26 16:21:06 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo and S. Covino (INAF/OABr) report on behalf of the MISTICI collaboration: We re-observed the field of the short GRB 070724A (Ziaeepour et al., GCN 6654) with the ESO-VLT equipped with FORS2 (see Covino et al. GCN 6666). An image subtraction analysis, performed with the ISIS package (Alard 200, A&AS, 144, 363) between the two imaging epochs (0.93 and 1.84 days after the burst, respectively), revealed that neither the galaxy reported by Bloom (GCN 6658) and Cenko et al. (GCN 6664) nor the object reported by Cenko et al. (GCN 6664) varied. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6675 SUBJECT: GRB 070724B: Swift-XRT afterglow likely candidate DATE: 07/07/27 17:52:01 GMT FROM: Pat Romano at OAB-Swift P. Romano, C. Guidorzi(Uni-Bicocca and OAB), A. Moretti(OAB), M. Chester(PSU) report on behalf of the Swift-XRT team: We have analysed all downlinked Swift-XRT data obtained for GRB 070724B detected by SuperAGILE (Feroci et al., GCN Circ. 6668), for a total of 7973s of Photon Counting (PC) mode data, beginning on 2007-07-25 18:32:39 UT. Of the two sources proposed in Romano et al. (GCN Circ. 6669), we can exclude number 2 (RA, Dec= 17.51024, 57.81898) as an afterglow candidate since no fading is found in X-ray data and there is a catalogued V=11.6 star within the XRT error circle (2.9 arcsec away). We propose source number 1 as the most likely afterglow candidate. The Photon Counting mode image provides a refined XRT position at RA,DEC(J2000)=17.48497, 57.67616, which is RA(J2000) = 01 09 56.39 Dec(J2000) = +57 40 34.2 with an uncertainty of 4.0 arcsec (radius, 90% containment). This is 1.5 arcsec from the initial X-ray position (Romano et al., GNC Circ. 6669) and 4.6 arcmin from the initial SuperAGILE position (Feroci et al., GCN Circ. 6668). The light curve exhibits a fading behaviour, with a power-law slope of 1.1+/-0.3. The spectrum (150 photons) can be fit using Cash statistics with an absorbed power law with a photon index of 2.6+/-0.5 and a column density of (9+/-3)E21 cm^-2 in excess of the Galactic value (3.1E21 cm^-2; Kalberla et al. 2005). The absorbed (unabsorbed) 0.3-10.0keV flux for the spectrum is 1.2E-12 (4.4E-12) ergs cm^-2 s^-1, at mean time of T+1.54d. Since the second set of XRT data were taken with an offset with respect to the first set (GCN Circ. 6669), more of the SuperAGILE error circle was covered. A new, weak source was found (Source number 3) at RA,DEC(J2000)=17.24912, 57.79786, or RA(J2000) = 01 08 59.79, Dec(J2000) = +57 47 52.3 with an uncertainty of 6.0 arcsec (radius, 90% containment). This position lies 14.2 arcmin from the SuperAGILE position (GCN Circ. 6668). The current observed 0.3-10 keV count rate is (5.3+/-1.6)E-03 counts/s, which translates into a 0.3-10 keV flux of ~2.6E-13 erg/cm2/s (assuming a power-law with photon index=2 absorbed by a column of NH=E21 cm-2). Further observations with Swift are planned. This circular is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6677 SUBJECT: GRB 070724B: Swift/UVOT Upper limits DATE: 07/07/28 15:46:01 GMT FROM: Margaret Chester at PSU M.M. Chester (PSU) and P. Romano (Uni-Bicocca and OAB) report on behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 070724B (detected by SuperAGILE; Feroci et al., GCN Circ. 6668) beginning 2007-07-27 00:02:11 UT, 48.6 hours after the burst trigger time. We do not find any new source in any of the UVOT observations inside the refined Swift/XRT error circle for the likely candidate, source #1 (RA,DEC(J2000)= 17.48497, 57.67616, Romano et al., GCN Circ. 6675). We note a cataloged star, V=18.2, 7.6 arcsec from the XRT position. The 3-sigma upper limits for detecting a source inside the XRT error circle in the co-added frames are: Filter Tstart Tstop Exp Magnitude (s) (s) (s) (3-sigma UL) White 179270 197091 1776 21.3 v 175022 196602 2023 19.8 The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.51 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6679 SUBJECT: GRB 070724B: P60 Observations DATE: 07/07/29 02:48:25 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko and A. Rau (Caltech) report on behalf of a larger collaboration: We have imaged the field of GRB070724B (Feroci et al., GCN 6668), the first GRB detected by SuperAGILE, with the automated Palomar 60-inch telescope. Observations consisted of 5 x 180 s images in the i' filter at a mean epoch of approximately UT 06:46:30 on 2007 July 26 (~ 31.3 hours after the burst). We do not detect any sources inside the error circle of the likely XRT afterglow (Romano et al., GCN 6675) to a limiting magnitude of i' > 21.0 (calculated with respect to several USNO-B stars in the field). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6687 SUBJECT: GRB 070724B: pseudo-z ~ 1.10 from prompt emission spectrum DATE: 07/07/30 15:54:19 GMT FROM: Alexandre Pelangeon at LATT,OMP,Toulouse A. Pelangeon & J-L. Atteia (LATT-OMP) report: We have used the spectral parameters obtained for the most intense part of GRB 070724B -- from T0+24.8 to T0+41.2 s, Konus time (V. Pal'shin, Ioffe Inst., private communication) -- observed by Konus-Wind (Golenetskii et al., GCNC 6671) to compute the spectral pseudo-redshift(**) of the first burst localized by SuperAGILE (Feroci et al., GCNC 6668). We obtain: pz= 1.10 +/- 0.20 We thank V. Pal'shin for having kindly performed the spectrum analysis and providing us the spectral parameters. (**) cf. http://www.ast.obs-mip.fr/grb/pz //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6703 SUBJECT: GRB 070724B: Swift-XRT afterglow confirmation DATE: 07/08/03 09:02:34 GMT FROM: Pat Romano at OAB-Swift P. Romano, C. Guidorzi(Uni-Bicocca and OAB), A. Moretti(OAB), report on behalf of the Swift-XRT team: Using all data collected by Swift/XRT obtained for GRB 070724B detected by SuperAGILE (Feroci et al., GCN Circ. 6668), for a total of 16.5 ks (between T+19.1 hours and T+7.5 days), we can now confirm that the candidate proposed in GCN Circ. 6675 (Romano et al.) is the afterglow of GRB 070724B. Its final position is RA,DEC(J2000)=17.48477,57.67620, which is RA(J2000) = 01 09 56.34 Dec(J2000) = +57 40 34.3 with an uncertainty of 3.9 arcsec (radius, 90% containment). This is 0.4 arcsec from the X-ray position given in Romano et al., GCN Circ. 6675) and 4.6 arcmin from the initial SuperAGILE position (Feroci et al., GCN Circ. 6668). The light curve can be fit with a power-law power-law with slope of 1.19+0.23-0.19 (90% cl). No further observations with Swift are planned. This circular is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6740 SUBJECT: No radio detection in superAGILE burst 070724B DATE: 07/08/10 13:00:06 GMT FROM: Poonam Chandra at U Virginia/NRAO Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of the Caltech-NRAO-Carnegie GRB Collaboration: "We used the Very Large Array to observe the field of view toward first superAGILE burst GRB 070724B (GCN 6668) at a frequency of 8.46 GHz on 2007 August 5th at 10.3 UT. The GRB is undetected and the peak radio brightness at the SWIFT-XRT position (GCN 6703) is -25 uJy ± 36 uJy. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."