//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9417 SUBJECT: GRB 090520 Swift-BAT detection of a burst in ground analysis DATE: 09/05/21 21:04:47 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): On May 20, 2009 at 01:37:16 UT, BAT triggered on GRB 090520 (trigger #352671). The burst was weak, and the instrument failed to find a source in onboard analysis. A significant source was found in ground analysis. The source is located at RA, Dec 11.613, -8.000 deg, which is RA(J2000) = 00h 46m 27.1s Dec(J2000) = -08d 00' 00" with an uncertainty of 3 arcmin (radius, sys+stat, 90% containment). The partial coding was 48%. The burst consisted of a single FRED pulse, starting about T-2 seconds, with a T90 of 20 ± 5 seconds (estimated error including systematics). The BAT event data for failed triggers is limited to 10 seconds. Using 10 seconds of event data from T-2 to T+8 seconds, the best fit to the spectrum is a simple powerlaw with a photon index of 0.8 +- 0.2. The fluence for this interval in the 15-150 keV band was 3.4 ± 0.5 x 10-7 ergs/cm2 (68% confidence). The BAT source position was about 3 arcmin from a low-redshift galaxy, 6dFGS gJ004613.4-080000. This is an emission-line galaxy at z = 0.0850. A Swift TOO was requested, but initially the source was in the Swift Moon constraint. In any case was 52 degrees (~2.5 hours in RA) from the Sun, not in constraint, but still an unfavorable angle, so no Swift followup observation is planned. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9420 SUBJECT: GRB 090520: GROND upper limits DATE: 09/05/22 23:53:35 GMT FROM: Andrea Rossi at TLS Tautenburg A. Rossi (Tautenburg), T. Kruehler and J. Greiner (both MPE Garching) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405) at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile) started follow-up observations of GRB 090520 (Cummings et al. 2009, GCN #9417) on May 21, at 09:35 UTC (~32 h after the burst). In addition, a second epoch of imaging was obtained, which started on May 22, 09:37 UTC. Image subtraction does not reveal any variable source between the two epochs. The first epoch thus yields the following upper limits: g > 23.8 r > 24.0 i > 23.4 z > 23.2 J > 21.8 H > 21.4 K > 20.8 obtained using the GROND zeropoints and 2MASS field stars as reference. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9427 SUBJECT: GRB 090520B: Fermi GBM detection DATE: 09/05/28 13:19:11 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) report on behalf of the Fermi GBM Team: "At 19:57:53.98 UT on 20 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090520B (trigger 264542275 / 090520832). [which was the second GRB trigger of the day while the first was detected by the Swift-BAT (Cummings et al. 2008, GCN 9417)] The on-ground calculated location, using the GBM trigger data, is RA = 332.0, DEC = 43.2 (J2000 degrees, equivalent to 22 h 08 m, 43 d 12'), with an uncertainty of 12 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 10 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 1.5 s (8-1000 keV). The time-averaged spectrum from T0-0.384 s to T0+0.256 s is adequately fit by a simple power law function with index -1.4 +/- 0.1 (chi squared 98 for 122 d.o.f.). The event fluence (8-1000 keV) in this time interval is (4.5 +/- 0.2)E-7 erg/cm^2. The 1-sec peak photon flux measured starting from T0 s in the 8-1000 keV band is 4.1 +/- 0.2 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: 9428 SUBJECT: GRB 090520C: Fermi GBM detection DATE: 09/05/28 13:32:02 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) report on behalf of the Fermi GBM Team: "At 20:23:19.31 UT on 20 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090520C (trigger 264543801 / 090520850). The on-ground calculated location, using the GBM trigger data, is RA = 111.2, DEC = -19.7 (J2000 degrees, equivalent to 07 h 24.8 m, -19 d 42'), with an uncertainty of 1.2 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 71 degrees. The GBM light curve consists of single peak with a duration (T90) of about 4.9 s (10-1000 keV). The time-averaged spectrum from T0-0.512 s to T0+3.968 s is adequately fit by a Band function with Epeak = 204.2 +/- 27.9 keV, alpha = -0.73 +/- 0.09, and beta = -1.96 +/- 0.10 (chi squared 400.9for 362 d.o.f.). The event fluence (8-1000 keV) in this time interval is (3.54 +/- 0.25)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.872 s in the 8-1000 keV band is 4.47 +/- 0.32 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: 9429 SUBJECT: GRB 090520D: Fermi GBM detection DATE: 09/05/28 13:45:04 GMT FROM: Narayana Bhat at U Alabama/Huntsville/GBM P. N. Bhat (UAH) reports on behalf of the Fermi GBM Team: "At 21:01:37.14 UT on 20 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090520D (trigger 264546099 / 090520876). The on-ground calculated location, using the GBM trigger data, is RA = 131.3, DEC = -18.0 (J2000 degrees, equivalent to 08 h 45.2 m, -18 d 0'), with an uncertainty of 4.3 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 66 degrees. The GBM light curve consists of single pulse with a duration (T90) of about 12 s (8-1000 keV). The time-averaged spectrum from T0-5.12 s to T0+13.3 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -1.03 +/- 0.22 and the cutoff energy, parameterized as Epeak, is 47.4 +/- 4.1 keV (chi squared 354 for 363 d.o.f.). The event fluence (8-1000 keV) in this time interval is (4.0 +/- 0.9)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.0 s in the 8-1000 keV band is 4.1 +/- 1.0 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 353.8 for 362 d.o.f.) with Epeak= 46.3 +/- 5.3 keV, alpha = -0.99 +/- 0.28 and beta = -3.25 +/- 1.23. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."