//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22524 SUBJECT: GRB 180324A: Swift detection of a burst DATE: 18/03/24 04:50:01 GMT FROM: David Palmer at LANL E. Sonbas (Adiyaman Univ.), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 04:37:09 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180324A (trigger=817345). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 76.585, +56.725 which is RA(J2000) = 05h 06m 20s Dec(J2000) = +56d 43' 29" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a small precursor about 5 seconds before the main, short, peak for a total duration of about 6 sec. The peak count rate was ~8000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 04:38:17.4 UT, 67.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 76.52896, 56.71298 which is equivalent to: RA(J2000) = 05h 06m 06.95s Dec(J2000) = +56d 42' 46.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 118 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 http://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 in excess of the Galactic value (3.81 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 7.1 (+6.82/-5.48) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 71 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 expected extinction corresponding to E(B-V) of 0.90. Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com). 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: 22525 SUBJECT: GRB 180324A: Prompt enhanced Swift-XRT position DATE: 18/03/24 05:18:47 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Using promptly downlinked XRT event data for GRB 180324A, we find an enhanced XRT position of the afterglow: RA, Dec: 76.5270, 56.7137 which is equivalent to: RA (J2000) = 05 06 06.49 Dec (J2000) = +56 42 49.2 with an uncertainty of 2.0 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/817345. Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22527 SUBJECT: GRB 180324A: KAIT Optical Upper Limit DATE: 18/03/24 06:07:20 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRB 180324A (Sonbas et al., GCN 22524) starting at 04:54:12 UT, ~17 minutes after the burst, and lasted ~10 minutes before it reached the physical limit of the telescope. Observations were performed with an automatic sequence in the clear (roughly R), and I filters, and the exposure time was 20 s per image. We do not detect any optical afterglow candidate within the enhanced XRT position error circle (Evans et al., GCN 22525). The typical limiting magnitude of our single clear image is about 19.0 mag calibrated to the APASS catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22528 SUBJECT: GRB 180324A: RATIR Optical Observations and Possible Afterglow Detection DATE: 18/03/24 07:16:36 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 180324A (Sonbas, et al., GCN 22524) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2018/03 24.19 to 2018/03 24.23 UTC (2.4 minutes to 0.92 hours after the BAT trigger), obtaining a total of 0.66 hours exposure in the r and i bands. We detect a weak source within the Swift-XRT error circle (Evans, et al., GCN 22525) in our first 80 s exposure, i-band image only. In comparison with the USNO-B1 catalog, we find i=20.15+/-0.37. The source is not on the frame in the subsequent image and is not detected in the next possible frame 3.5 minutes later. In our full 0.66 hour exposure time, the source is not detected with the following upper limits (3-sigma): r > 22.08 i > 22.04 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. If the detection in the first frame is due to the afterglow, then the afterglow faded rapidly. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22529 SUBJECT: GRB 180324A: Enhanced Swift-XRT position DATE: 18/03/24 09:18:29 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 2334 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180324A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 76.52652, +56.71430 which is equivalent to: RA (J2000): 05h 06m 6.37s Dec (J2000): +56d 42' 51.5" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22530 SUBJECT: GRB 180324A: Swift-XRT refined Analysis DATE: 18/03/24 10:19:31 GMT FROM: Phil Evans at U of Leicester J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U. Leicester) and E. Sonbas report on behalf of the Swift-XRT team: We have analysed 7.1 ks of XRT data for GRB 180324A (Sonbas et al. GCN Circ. 22524), from 80 s to 13.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 22525). The late-time light curve (from T0+5.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.07 (+/-0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.36 (+0.13, -0.12). The best-fitting absorption column is 9.0 (+1.6, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 3.8 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.7 x 10^-11 (8.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 9.0 (+1.6, -1.4) x 10^21 cm^-2 Galactic foreground: 3.8 x 10^21 cm^-2 Excess significance: 5.9 sigma Photon index: 1.36 (+0.13, -0.12) If the light curve continues to decay with a power-law decay index of 1.07, the count rate at T+24 hours will be 0.032 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x 10^-12 (2.8 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00817345. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22531 SUBJECT: GRB 180324A: Swift/UVOT Upper Limits DATE: 18/03/24 23:27:32 GMT FROM: Sam LaPorte at PSU GRB 180324A: Swift/UVOT Upper Limits S. J. Laporte (PSU) and E. Sonbas (Adiyaman Univ.) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180324A 72 s after the BAT trigger (Sonbas et al., GCN Circ. 22524). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 22529) or RATIR position (Butler et al. GCN Circ. 22528) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 72 221 147 >19.8 u_FC 284 534 246 >19.3 white 72 12383 1552 >21.3 v 614 13894 1172 >19.5 b 539 8158 549 >20.9 u 284 7992 814 >20.3 w1 664 7787 471 >20.2 w2 6970 13290 1082 >21.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.90 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22533 SUBJECT: GRB 180324A, Swift-BAT refined analysis DATE: 18/03/25 02:06:18 GMT FROM: Amy Lien at GSFC H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), D. M. Palmer (LANL), T. Sakamoto (AGU), E. Sonbas (Adiyaman Univ.), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180324A (trigger #817345) (Sonbas et al., GCN Circ. 22524). The BAT ground-calculated position is RA, Dec = 76.581, 56.744 deg which is RA(J2000) = 05h 06m 19.4s Dec(J2000) = +56d 44' 36.8" with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%. The mask-weighted light curve shows a small precursor at ~T-5 s, followed by the main pulse that starts at ~T-0.2, peaks at ~T+0.3 s, and ends at ~T+1 s. There is also some weak emission that lasts till ~T+4 s. T90 (15-350 keV) is 7.2 +- 1.3 sec (estimated error including systematics). The lag analysis for the main pulse finds a lag of 48 +- 18 ms for the 100-350 keV to 25-100 keV band. This value is consistent with that of a long GRB. In addition, no extended emission is found after ~T+4 s. The time-averaged spectrum from T-5.4 to T+3.7 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.45 +- 0.14. The fluence in the 15-150 keV band is 5.6 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.13 sec in the 15-150 keV band is 4.4 +- 0.3 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/817345/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22547 SUBJECT: Konus-Wind observation of GRB 180324A DATE: 18/03/26 13:27:09 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: GRB 180324A (Swift-BAT trigger 817345: Sonbas et al., GCN 22524; Krimm et al., GCN 22533) triggered Konus-Wind at T0=16629.939 s UT (04:37:09.939) The burst light curve shows a weak pulse, which started at ~T0-0.4 s and peaked at ~T0 s. The total duration of the burst is ~0.7 s. The emission is seen up to ~0.5 MeV. As observed by Konus-Wind, the burst had a fluence of (7.4 ± 2.1)x10^-7 erg/cm2 and a 64-ms peak energy flux, measured from T0, of (1.8 ± 0.5)x10^-6 erg/cm2 (both in the 20 keV - 10 MeV energy range). The burst spectrum (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 15 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -0.56(-0.71,+1.16), and the peak energy Ep = 154(-38,+77) keV, chi2 = 22/19 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep, and an upper limit on beta of ~-2.2 The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180324_T16629/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.