//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9688 SUBJECT: GRB 090720: Fermi GBM detection DATE: 09/07/20 14:44:23 GMT FROM: Arne Rau at MPE Arne Rau (MPE) reports on behalf of the Fermi GBM Team: "At 06:38:08.28 UT on 20 July 20009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090720 (trigger 269764690 / 090720276). The on-ground calculated location, using the GBM trigger data, is RA = 199.5, DEC = -16.4 (J2000 degrees, equivalent to 13 h 18 m, -16 d 24 '), with an uncertainty of 5.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 113 degrees. This burst was also independently detected (but not triggered) by INTEGRAL SPI-ACS. The GBM light curve shows a single peak with a duration (T90) of about 7.0 s (8-1000 keV). The time-averaged spectrum from T0-1.856 s to T0+5.312 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.75 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 117.50 +/- 7.12 keV (chi squared 507 for 507 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.9 +/- 0.1)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+0.002 s in the 8-1000 keV band is 10.9 +/- 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: 9694 SUBJECT: GRB 090720 Source found in ground processing of Swift-BAT data DATE: 09/07/20 17:35:54 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. R. Cummings (NASA/GSFC/CRESST), S. Holland (NASA/GSFC/CRESST), M. Stamatikos (NASA/ORAU) on behalf of the Swift Team At 06:38:08 on July 20, 2009 Swift-BAT rate-triggered on GRB 090720 (BAT trigger #357811). The burst was also detected by the Fermi GBM (trigger #269764690, Rau, GCN #9688). No source was found onboard in automated processing. A significant source on the edge of the BAT field of view was found in ground processing. The position was RA, Dec 203.694, -10.335, which is equivalent to: RA (J2000) 13h 34m 46.6s Dec (J2000) -10d 20m 06s with an error radius of 3 arcmin (estimated 90% containment). This was 6 degrees from the Fermi GBM ground position, just outside the GBM 1-sigma radius. As seen in BAT, the burst was a single weak pulse about 3 seconds long. A Swift TOO has been requested and approved. The Swift Burst Advocate for this burst is Erik Hoversten (hoversten at astro dot psu dot edu). 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: 9697 SUBJECT: Swift XRT and UVOT refned analysis of GRB 090720 DATE: 09/07/22 13:34:27 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU), S. R Oates (MSSL-UCL), E. A. Hoversten (PSU), P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift team: Swift XRT and UVOT started observing the field of GRB 090720 11 hours after the Fermi GBM and Swift/BAT triggers (Rau et al. GCN circ 9688, Cummings et al. GCN circ 9694). Using 1233 s of XRT Photon Counting mode data and one UVOT image, 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 = 203.68020, -10.33480 which is equivalent to: RA (J2000): 13 34 43.25 Dec (J2000): -10 20 05.3 with an uncertainty of 3.0 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, arXiv:0812.3662). Swift has continued observing the field of GRB 090720 and the source is clearly fading. Currently it is at a level of less than 1.6e-3 counts/s (or 5.0 e-14 ergs/s/cm2). Due to the low number of counts, no spectral analysis can be performed. With the Swift/UVOT, we do not detect any source at the Swift XRT position. The 3-sigma upper limits for the summed exposures is: Filter T_start(s) T_stop(s) Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- white 41,776 63,952 579 > 21.28 u 39,573 63,855 3513 > 21.10 ------------------------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.05 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). This circular is an official product of the Swift team. [GCN OPS NOTE(22jul09): Per author's request, in the 5th paragraph the "finding chart exposure" was changed to "summed exposures".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9698 SUBJECT: GRB 090720B: Fermi GBM detection DATE: 09/07/22 13:57:40 GMT FROM: Michael Burgess at UAH J. M. Burgess (UAH), A. Goldstein (UAH) and A. J. van der Horst (NASA/MSFC/ORAU) report on behalf of the Fermi GBM Team: "At 17:02:56.91 UT on 20 July 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090720B (trigger 269802178 / 090720710). The on-ground calculated location, using the GBM trigger data, is RA = 203.0, DEC = -54.8 (J2000 degrees, equivalent to 13h 32m, -54d 48'), with an uncertainty of 2.9 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 56 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of two bright peaks with a duration (T90) of about 20 s (8-1000 keV). The time-averaged spectrum from T0+0.0 s to T0+20.1 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -1.01 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 982 +/- 186 keV (chi squared 484 for 483 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.06 +/- 0.03)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.8 s in the 8-1000 keV band is 10.9 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 482 for 482 d.o.f.) with Epeak= 924 +/- 201 keV, alpha = -1.00 +/- 0.05 and beta = -2.43 +/- 0.47. The temporal and spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9699 SUBJECT: GRB 090720: Gemini-North Imaging and Optical Afterglow DATE: 09/07/22 16:00:14 GMT FROM: Antonino Cucchiara at PSU A. Cucchiara (PSU), S. B. Cenko (UC Berkeley), D. B. Fox (PSU), E. Ofek (Caltech), N. Tanvir (U. Leicester) report: "On April 21.26 UT and 22.24 UT we obtained two R-band images of the Fermi/Swift GRB 090720 (GCN 9688, 9694) with GMOS on the Gemini-North telescope for a total exposure time, at each epoch, of 15 minutes. In the coadded images we identify a possible R counterpart inside the XRT error circle (Grupe et al., GCN 9697) at the coordinates: RA (J2000): 13:34:43.33 Dec (J2000): -10:20:04.9 with an uncertainty of 0.5". The estimated magnitude at the two epochs are: R = 21.50 +- 0.03 mag R = 22.34 +- 0.04 mag The implied fading, by 0.84 +- 0.05 mag between our two epochs, is consistent with a power-law decay of index alpha=1.12 +- 0.11 referenced to the burst trigger time. We conclude from this fading behavior that the source is the optical afterglow of GRB 090720. Magnitude values are calibrated using the USNO B1 star at RA= 13:34:39.9 Dec= -10:20:17.06 which has tabulated magnitude R = 19.79. We thank the Gemini-N staff for the support in performing this observations, in particular Tom Geballe and Paul Hirst." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9700 SUBJECT: IPN Triangulation of bright GRB 090720B DATE: 09/07/22 16:08:03 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, A. von Kienlin, A. Rau, and K. Hurley on behalf of the INTEGRAL SPI-ACS GRB team, M. Marisaldi, F. Fuschino, C. Labanti, M. Galli, G. Di Cocco on behalf of the AGILE team, K. Yamaoka, M. Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, K. Makishima, and Y. Hanabata on behalf of the Suzaku-WAM team, and V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM team, report: Suzaku-WAM, Konus-Wind, AGILE-MCAL, and INTEGRAL (SPI-ACS) observed the bright GRB 090720B at about 17:02:57 UT (the Fermi/GBM trigger 269802178/090720710: Burgess et al. GCN 9698). We have triangulated this burst to a Konus-GBM annulus centered at RA(2000)=274.434 (18h 17m 44s) Dec(2000)=-23.965 (-23d 57' 54"), whose radius is 60.824 +/- 0.031 (3 sigma). Triangulation of the Konus-SPI-ACS gives an annulus centered at RA(2000)=274.426 (18h 17m 42s) Dec(2000)=-18.772 (-18d 46' 19"), whose radius is 64.910 +/- 0.252 (3 sigma). Together, these 2 annuli yield a 3-sigma error box whose center and corners are: ----------------------------------------------- RA(2000), deg Dec(2000), deg ----------------------------------------------- Center: 201.609 (13h 26m 26s) -55.000 (-55d 00' 01") Corners: 201.763 (13h 27m 03s) -59.798 (-59d 47' 54") 201.580 (13h 26m 19s) -58.693 (-58d 41' 36") 201.793 (13h 27m 10s) -50.725 (-50d 43' 29") 201.823 (13h 27m 17s) -51.627 (-51d 37' 36") ----------------------------------------------- The error box area is 0.500 sq. deg and may be refined. The GBM on-ground location (Burgess et al. GCN 9698) is consistent with the IPN box. A map is posted at http://www.ioffe.ru/LEA/GRBs/GRB090720_T61379/IPN/ showing GBM contours (statistical) and best-fit position (star), and the IPN annuli (solid lines with centers dot-dashed). This map will also be posted at http://ssl.berkeley.edu/ipn3/090720B . The IPN localization may be improved. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9701 SUBJECT: Konus-Wind observations of bright hard GRB 090720B DATE: 09/07/23 10:06:08 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: GRB 090720B (Fermi/GBM trigger 269802178/090720710: Burgess et al., GCN 9698; IPN localization box: Golenetskii et al., GCN 9700) triggered Konus-Wind at T0=61379.486 s UT (17:02:59.486). This bright hard GRB started with a series of several short spikes, followed by a smoother structure. The emission is seen above 10 MeV for the whole duration of the event (~16 s). The Konus-Wind light curves of this GRB are available at http://www.ioffe.ru/LEA/GRBs/GRB090720_T61379/ As observed by Konus-Wind the burst had a fluence of 1.8(-0.5,+0.7)x10-5 erg/cm2, and a 2-ms peak flux, measured from T0+0.186 s, of 8.3(-2.8,+4.1)x10-5 erg/cm2/s (both in the 20 keV - 15 MeV energy range). The time-integrated spectrum of the burst, measured from T0 to T0+16.640 s, is well fit (in the 20 keV - 15 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with alpha = -1.16(-0.13,+0.17), and Ep = 1370(-580,+1190)keV (chi2 = 99/98 dof). The spectrum at the maximum count rate, measured from T0+0.128 to T0+0.192 s, is also well fit (in the 20 keV - 15 MeV range) by a power law with exponential cutoff model, for which: alpha = -0.47(-0.42,+0.71), and Ep = 710(-280,+590)keV (chi2 = 7.3/8 dof). All the quoted values are preliminary. All the quoted errors are at the 90% confidence level.