//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8946 SUBJECT: GRB 090307: Swift-XRT afterglow confirmation and analysis DATE: 09/03/08 13:54:58 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT observed the field of GRB 090307 (BAT trigger 345551; GCN Circs. 8943, 8945) for 4.6 ks, from 135 s to 80 ks after the BAT trigger. All of the data were taken in Photon Counting (PC) mode. The X-ray source reported by Evans et al. (GCN Circ. 8943) is seen to fade, and is therefore identified as the afterglow, confirming the GRB nature of this BAT trigger. The source has an enhanced XRT position: RA, Dec = 244.9944, -28.6333 which is equivalent to: RA (J2000): 16 19 58.64 Dec (J2000): -28 37 59.9 with an uncertainty of 2.1 arcsec (radius, 90% confidence). The light curve shows a power-law decay, with an index 0.7 (+0.2, -0.1). The PC mode spectrum can be fitted with an absorbed power-law, with a photon index of 2.21 (+0.72, -0.60) and an absorbing column of 3.5 (+2.7,-1.1) e21 cm-2, in excess of the Galactic value of 1.3e21 cm-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10-11 (7.6 x 10-11) erg cm-2 count-1. If the light curve continues to decay with alpha=0.7, the XRT count-rate at T+48 hrs will be 0.002 counts s-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.38e-14 (1.4e-13) erg cm-2 s-1. The results of the automatic XRT analysis are available online at http://www.swift.ac.uk/xrt_products/00345551. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8959 SUBJECT: GRB 090307: GROND Upper Limits DATE: 09/03/09 13:45:36 GMT FROM: Christian Clemens at MPE A. C. Updike (Clemson University), C. Clemens, J. Greiner and P. Afonso (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 090307 (Swift trigger 345551; Barthelmy et al., GCN #8945) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 05:06 UT on March 7, 80 min after the GRB trigger, and continued for 66 min. They were performed at an average seeing of 1.2" and at an average airmass of 1.8. We do not detect a source within the Swift-XRT error circle reported by Evans et al. (GCN #8946) down to (all in AB system) g' > 23.3, r' > 23.7, i' > 23.2, z' > 22.9, J > 21.7, H > 21.2 and K > 20.3. The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.528 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8961 SUBJECT: GRB 090307B: Fermi GBM detection DATE: 09/03/09 15:16:17 GMT FROM: Elisabetta Bissaldi at MPE E.Bissaldi (MPE) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 04:00:58.60 UT on 07 March 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090307B (trigger 258091199 / 090307167). The on-ground calculated location, using the GBM trigger data, is RA = 158.6, DEC = -14.6 (J2000 degrees, equivalent to 10h 34m, -14d 36'), with an uncertainty of 9.7 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 83 degrees. This long GRB consists of one main FRED-like pulse with substructure, rising at T0-6 s and with a duration (T90) of about 30 s (8-1000 keV). T50 is about 15 s (8-1000 keV). The time-averaged spectrum from T0-6 s to T0+10.4 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.7 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 212 +/- 80 keV (chi squared 346 for 357 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.7 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-5 s in the 8-1000 keV band is 1.80 +/- 0.12 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: 8974 SUBJECT: GRB 090307A: TAROT Calern observatory optical observations DATE: 09/03/10 23:27:24 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Gendre, B. (LAM-OAMP), Boer M. (OHP-OAMP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 090307A detected by SWIFT (trigger 345551) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 373.3s after the GRB trigger The elevation of the field increased from 16 degrees above horizon and weather conditions were good. The first image has a duration of 90.0s. We do not detect any OT at the XRT position (Evans GCNC 8946) with a limiting magnitude of: t0+373.3s to t0+463.3s : R > 16.5 We co-added a series of exposures: t0+373.3s to t0+1062.0s : R > 18.9 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=348.7859 lat=+15.1296 and the galactic extinction in R band is ~1.4 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited.