//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22556 SUBJECT: Swift Trigger 819301: possible GRB 180329A DATE: 18/03/29 01:17:44 GMT FROM: David Palmer at LANL J. L. Racusin (NASA/GSFC), A. Deich (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:58:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located a marginal-significance (6.9 sigma) image peak that may be GRB 180329A (trigger=819301). Swift could not slew to the location due to an observing constraint. The BAT on-board calculated location is RA, Dec 329.298, -15.071 which is RA(J2000) = 21h 57m 11s Dec(J2000) = -15d 04' 14" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows some variation consistent with a ~8 second long GRB, however this variation is also consistent with the presence of the currently-active black hole transient MAXI J1820+070 in the FOV. The peak count rate was ~1400 counts/sec (15-350 keV), at ~5 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 23:07 UT on 2018 April 02. There will thus be no XRT or UVOT data for this trigger before this time. Due to the low significance of this detection, the presence of a bright variable X-ray source in the BAT Field of View, and the lack of follow-up observations from the XRT and UVOT, we cannot determine whether this is a GRB at this time. Further analysis of the full downlinked data will be required to decide if this is a GRB or a statistical fluctuation in the image plane. Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 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: 22561 SUBJECT: GRB 180329A: Swift-BAT refined analysis DATE: 18/03/29 22:26:04 GMT FROM: Amy Lien at GSFC C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC), 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+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180329A (trigger #819301) (Racusin et al., GCN Circ. 22556). The BAT ground-calculated position is RA, Dec = 329.314, -15.043 deg which is RA(J2000) = 21h 57m 15.3s Dec(J2000) = -15d 02' 36.0" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted light curve shows a weak pulse that starts at ~T0, peaks at ~T+1 s, and ends at ~T+10 s. T90 (15-350 keV) is 9.1 +- 1.8 sec (estimated error including systematics). The time-averaged spectrum from T-0.30 to T+9.69 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.39 +- 0.31. The fluence in the 15-150 keV band is 2.3 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.14 sec in the 15-150 keV band is 0.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. Due to an observing constraint, there are no observations of this source with the Swift XRT or UVOT, and hence no confirmation of the nature of the source. However, because the image significance from the ground analysis of the BAT data is ~ 9 sigma, and the temporal and spectral properties are consistent with those from a BAT GRB, we conclude that this source is likely a real GRB. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/819301/BA/