//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10526 SUBJECT: GRB 100319A: Swift detection of a burst; possible SGR DATE: 10/03/19 19:05:59 GMT FROM: Scott Barthelmy at NASA/GSFC J. M. Gelbord (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), T. Sakamoto (NASA/UMBC), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU), E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 18:34:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100319A (trigger=416485). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 278.442, -8.537 which is RA(J2000) = 18h 33m 46s Dec(J2000) = -08d 32' 13" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike structure with a duration of about 0.2 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0.0 sec after the trigger. The XRT began observing the field at 18:35:57.2 UT, 66.6 seconds after the BAT trigger. In promptly downlinked data we detect a low significance uncatalogued source at the following location (RA, Dec) = (278.43458, -8.51822), which is equivalent to: RA(J2000) = 18h 33m 44.3s, Dec(J2000) = -08d 31m 05.6s, with an uncertainty of 6.7 arcseconds (90% radius). This source lies 73 arcsecs from the BAT position. We await further downlinked data to confirm if this source is real. UVOT took a finding chart exposure of 150 seconds with the White filter starting 70 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 25% of the BAT 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 BAT 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. Given the proximity of this burst to the Galactic Plane (0.01 degrees), the shortness of the burst (16 ms trigger time) and soft emission (with no visible emission seen above 100 keV), this burst may be from an unknown Soft Gamma Repeater. We note that this is 23 arcmin from the center of the W41 supernova remnant in a region with several known pulsars. Burst Advocate for this burst is J. M. Gelbord (jgelbord AT astro.psu.edu). 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: 10528 SUBJECT: Swift-BAT refined analysis of the probable new SGR 1833-0832 DATE: 10/03/19 22:55:16 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), J. M. Gelbord (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+303 sec from the recent telemetry downlink, we report further analysis of BAT trigger #416485 (Gelbord, et al., GCN Circ. 10526). The BAT ground-calculated position is RA, Dec = 278.446, -8.533 deg, which is RA(J2000) = 18h 33m 47.1s Dec(J2000) = -08d 32' 00.2" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 87%. The mask-weighted light curve shows two resolved peaks with a total duration of ~16 millisec. T90 (15-350 keV) is 0.012 +- 0.009 sec (estimated error including systematics). The time-averaged spectrum from T+0.000 to T+0.016 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -1.02 +- 1.35, and Epeak of 38.2 +- 5.0 keV (chi squared 43.5 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-8 erg/cm2 and the 1-sec peak flux measured from T-0.49 sec in the 15-150 keV band is 0.2 +- 0.1 ph/cm2/sec. Similarly, a blackbody fit yields kT= 10.0 +-1.2 keV (chi squared 43.8 for 57 d.o.f). A fit to a simple power law gives a photon index of 2.58 +- 0.23 (chi squared 74.2 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/416485/BA/ Given (a) the low galactic lattitude (0.01 deg), (b) the short duration of the event, and (c) the spectral softness (Epeak=38.2 and photon index of -1.02), we believe this to be an event from a new probable SGR which we are calling SGR 1833-0832. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10529 SUBJECT: Swift-XRT refined position of the probable new SGR 1833-0832 DATE: 10/03/20 02:07:00 GMT FROM: Jonathan Gelbord at PSU/Swift J.M. Gelbord (PSU) and L. Vetere (PSU) report on behalf of the Swift-XRT team: We have analysed 959 s of XRT data for BAT trigger #416485 (Gelbord et al. GCN Circ. 10526), from 80 s to 1.3 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The refined XRT position for this burst is RA, Dec 278.435, -8.519 which is equivalent to RA(J2000) = 18h 33m 44.4s Dec(J2000) = -08d 31m 08.4s with an uncertainty of 5.3 arcsec (radius, 90% confidence). This position may be improved as more data are received. We note that this position is 3.5 arcsec from the XRT position and 63.5 arcsec from the BAT position reported by Gelbord et al. (GCN Circ. 10526). At this time we cannot confirm whether the source is decaying. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10532 SUBJECT: GRB 100319A: correction to GCN 10527 DATE: 10/03/20 15:10:11 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs Vladimir Lipunov I am sorry for mistakes in GCN 10527. The Title: GRB 100319A: MASTER-Net optical alert observations Result: There is no OT on the first 20-s exposition time image inside Swift XRT error box (Gelbord et al., GCN CIRC 10526) brighter 16.0. The message may be cited. mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10534 SUBJECT: Discovery of the Spin Period of SGR 1833-0832 DATE: 10/03/20 16:22:48 GMT FROM: Ersin Gogus at Sabanci U/Turkey Ersin Gogus (Sabanci Univ), Tod Strohmayer (NASA/GSFC), Chryssa Kouveliotou (NASA/MSFC), Peter Woods (Dynetics) Discovery of the Spin Period of SGR 1833-0832 Following the Swift detection of a burst from the new Soft Gamma Repeater SGR 1833-0832 (Gelbord, J. et al. 2010, GCN #10526) we triggered our SGR ToO Program with RXTE. A 1.3 ks RXTE observation started on 2010 March 19, 21:49:52UT. We detect coherent pulsations from the new SGR in the 2-20 keV PCA data at 0.1321 Hz, corresponding to a spin period of 7.57 sec. We then performed timing analysis on 22.5 ks Swift/XRT data in PC mode and confirmed the period detection as 7.5654(1) s. We note that there is no previously known X-ray source in the RXTE field of view with such periodicity. The detected coherent pulsations likely indicate the spin period of the newly discovered, burst-active SGR. We thank the RXTE planner, Divya Pereira for the prompt scheduling of the RXTE observations and Scott Barthelmy, Jonathan Gelbord and Neil Gehrels from the Swift team for valuable and prompt information exchange on this new source. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10535 SUBJECT: Possible pulsation period in SGR 1833-0832 DATE: 10/03/20 16:31:28 GMT FROM: Paolo Esposito at INAF-IASF,Milano Paolo Esposito, Gian Luca Israel, Luigi Stella, Nanda Rea, Andrea Tiengo report: We analysed 22.5 ks of XRT data in Photon Counting (PC) mode of the new soft gamma-ray repeater candidate SGR 1833-0832 (Gelbord et al. GCN Circ. 10526, 10531). The data were barycentered using the X-ray position reported in Evans et al. (GCN Circ. 10530). We detect strong pulsations from the X-ray source in the 2-10 keV band at 7.5653(5) sec. The background subtracted pulsed fraction, defined as the semiamplitude of sinusoidal modulation divided by the mean source count rate, is 64+/-4%. The pulse is highly significant (the probability of such a signal to appear by chance in the search, taking into account the 32768 trials, is about 5E-18) and is not present in the background data. We caution however that this value is close to three times the XRT PC frame time, 2.507 s. At the link below a plot of the source and background data folded at our best fit period and at 3*2.507 s can be seen. Further observations are needed to confirm this period. http://www.iasf-milano.inaf.it/~paoloesp/sgr1833.html [GCN OPS NOTE(20mar10): Per author's request the Subject (a result of a copy-pase mistake) was changed to "Possible pulsation period in SGR 1833-0832".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10536 SUBJECT: SGR 1833-0832 is pulsed at 7.56 seconds DATE: 10/03/20 16:32:56 GMT FROM: David Palmer at LANL David Palmer (LANL) and J. M. Gelbord (PSU), on behalf of the Swift Team, reports: Analysis of the XRT data from T+80s to T+15 hours from the new probable SGR 1833-0832 (Gelbord et al. GCN Circ. 10526) shows strong pulsations at an unbarycentered period of 7.5646(3) s. The detection of pulsations, combined with the other SGR-like features of this event, strongly indicate that this object is a new discovery of a Soft Gamma Repeater, and should be monitored for further bursts.