//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29601 SUBJECT: GRB 210306B: Swift detection of a burst DATE: 21/03/06 09:54:05 GMT FROM: Scott Barthelmy at NASA/GSFC E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), K. L. Page (U Leicester) and T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift Observatory Team: At 09:32:14 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210306B (trigger=1036024). Swift did not slew to the burst because of Sun constraint. The BAT on-board calculated location is RA, Dec 331.848, +10.175 which is RA(J2000) = 22h 07m 23s Dec(J2000) = +10d 10' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a few peaks structure with a duration of at least 15 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew to this target. There will be no XRT or UVOT data. Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it). 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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29612 SUBJECT: GRB 210306B: Swift-BAT refined analysis DATE: 21/03/07 13:14:21 GMT FROM: Takanori Sakamoto at AGU A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210306B (trigger #1036024) (D'Ai, et al., GCN Circ. 29601). The BAT ground-calculated position is RA, Dec = 331.813, 10.152 deg which is RA(J2000) = 22h 07m 15.1s Dec(J2000) = +10d 09' 06.8" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 21%. The BAT light curve showed a multi-peaked structure that starts at T-2 s and ends at ~T+25 s. T90 (15-350 keV) is 24.32 +- 2.45 sec (estimated error including systematics). The time-averaged spectrum from T-2.42 to T+24.63 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.38 +- 0.20. The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.04 sec in the 15-150 keV band is 2.4 +- 0.5 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1036024/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29637 SUBJECT: GRB 210306B: Fermi GBM detection DATE: 21/03/09 17:13:46 GMT FROM: Stephen Lesage at Fermi-GBM Team S. Lesage (UAH), A. von Kienlin (MPE), and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 09:32:14.42 UT on 06 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210306B (trigger 636715939 / 210306397) which was also detected by the Swift/BAT (Ambrosi et al. 2021, GCN 29601). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 37 degrees. The GBM light curve shows a single-peaked structure with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-1.3 s to T0+14.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.0 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 73 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.0 s in the 10-1000 keV band is 2.7 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"