//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27373 SUBJECT: Swift-BAT trigger 960986: Swift detection of a new SGR Swift J1818.0-1607 DATE: 20/03/12 21:47:38 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), T. Sakamoto (AGU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:16:47 UT, the Swift Burst Alert Telescope (BAT) triggered and located a new SGR (trigger=960986). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 274.471, -16.102 which is RA(J2000) = 18h 17m 53s Dec(J2000) = -16d 06' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peak structure with a duration of about 0.1 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 21:17:51.2 UT, 64.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 274.5009, -16.1312 which is equivalent to: RA(J2000) = 18h 18m 00.22s Dec(J2000) = -16d 07' 52.3" with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 147 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. UVOT took a finding chart exposure of 150 seconds with the White filter starting 68 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain, extinction expected. The extremely short and relatively soft nature of the BAT detection, combined with the source's closeness to the Galactic Plane (b=-0.14 deg), is suggestive that this trigger is from a previously undiscovered SGR. If this is a new SGR and not a GRB, we name the source Swift J1818.0-1607. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 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: 27378 SUBJECT: SGR Swift J1818.0-1607: BOOTES-4/MET optical limit DATE: 20/03/13 05:26:09 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. Xiong, Y. Fan, X. Zhao, J. Bai, C. Wang, Y. Xin (Yunnan Observatories of CAS), on behalf of a larger collaboration, report: Following the detection of SGR Swift J1818.0-1607 by Swift (Evans et al. GCNC 27373), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) gathered images starting at 21:17:34 UT (47 s after trigger). No optical afterglow is found down to 19.3 mag (in co-added 10x10 s unfiltered images) within the Swift/XRT error box, consistent with the non-detection by Swift/UVOT (Evans et al. GCNC 27373). Further observations are ongoing. [GCN OPS NOTE(14mar20): Per author's request, Y.Xin's affiliation was changed from "Yunnan Nacional Astronomical Observatory" to "Yunnan Observatories of CAS".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27384 SUBJECT: SGR Swift J1818.0-1607: Swift-BAT refined analysis DATE: 20/03/14 05:40:49 GMT FROM: Takanori Sakamoto at AGU M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. A. Evans (U Leicester), H. A. Krimm (NSF),S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of the BAT detection of a burst from a newly discovered SGR Swift J1818.0-1607 (trigger #960986) (Evans, et al., GCN Circ. 27373). The BAT ground-calculated position is RA, Dec = 274.515, -16.125 deg which is RA(J2000) = 18h 18m 03.7s Dec(J2000) = -16d 07' 31.8" with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted light curve in 2 ms time bins shows a burst that starts at T-0.005 sec, peaks at T+0.002 sec and ends at T+0.015 sec. There is a hint of a second pulse around T+0.01 s. T90 (15-350 keV) is ~0.01 sec. The time-averaged spectrum from T+0.00 to T+0.01 sec fit by a simple power-law model shows the power law index of 3.17 +- 0.63 (chi squared 51.9 for 57 d.o.f.). The fluence in the 15-150 keV band is 2.9 +- 1.1 x 10^-9 erg/cm2. The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band is 8.7 +- 3.1 ph/cm2/sec. A single blackbody fit to the time-averaged spectrum shows the blackbody temperature of 5.5 +- 0.9 keV (chi squared 43.2 for 57 d.o.f.). A thermal bremsstrahlung model fit shows the temperature of 15.8 +- 6.5 keV (chi squared 48.7 for 57 d.o.f.). 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/960986/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27696 SUBJECT: Swift Detection of a burst from SGR Swift J1818.0-1607 DATE: 20/05/06 17:55:55 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:36:50 UT, the Swift Burst Alert Telescope (BAT) triggered on Swift J1818.0-1607 (trigger=969823). Swift slewed immediately to the source. The BAT on-board calculated location is RA, Dec 274.498, -16.152, which is RA(J2000) = 18h 18m 00s Dec(J2000) = -16d 09' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike with a duration of about 0.3 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 17:37:52.5 UT, 62.6 seconds after the BAT trigger. Using promptly downlinked data we find an X-ray source with an enhanced position: RA, Dec 274.5008, -16.1312 which is equivalent to: RA(J2000) = 18h 18m 00.18s Dec(J2000) = -16d 07' 52.3" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 75 arcseconds from the BAT onboard position, within the BAT error circle, and consistent with the known position of Swift J1818.0-1607. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.35 x 10^22 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 65 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the large, but uncertain, extinction expected. This source was first reported on 2020 March 12 (GCN #27373; Evans et al.) Since then it has been monitored every 3-7 days with Swift follow-up observations.