GRB180925A

This page lists all entries on GRB180925A in GRBweb

Summary IPN Swift GCN 23268 GCN 23270 GCN 23271 GCN 23272 GCN 23273 GCN 23274 GCN 23275 GCN 23276 GCN 23291 GCN 23304

Summary table
Variable Value Source
T0 14:37:30.967 UTC GCN_circulars,Konus-Wind Det
ra 315.2029° Swift
decl -64.4569° Swift
pos_error 2.85e-05° Swift
T90 81.7 s Swift
T90_start 14:37:31 UTC Swift
fluence 4.10e-06 erg/cm² Swift
T100 81.733 s
GBM_located False
mjd 58386.60938619213 GCN_circulars,Konus-Wind Det
IPN table
GRB_name GRB180925A
ra 315.2125°
decl -64.4500°
pos_error 5.00e-02°
Swift table
GRB_name GRB180925A
t_trigger 14:37:31 UTC
ra 315.2029°
decl -64.4569°
pos_error 2.85e-05°
T90 81.7 s
fluence 4.10e-06 erg/cm²
GCN 23268 table
GRB_name GRB180925A
GCN_number 23268
Detection_method Swift Det
t_trigger 14:37:31 UTC
ra 315.2130°
decl -64.4430°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23268 SUBJECT: GRB 180925A: Swift detection of a burst DATE: 18/09/25 14:51:09 GMT FROM: David Palmer at LANL J.D. Gropp (PSU), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU), R. L. C. Starling (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:37:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180925A (trigger=863421). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 315.213, -64.443 which is RA(J2000) = 21h 00m 51s Dec(J2000) = -64d 26' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of at least 30 sec. The peak count rate was ~3500 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 14:39:20.8 UT, 108.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 315.20546, -64.45727 which is equivalent to: RA(J2000) = 21h 00m 49.31s Dec(J2000) = -64d 27' 26.2" with an uncertainty of 4.5 arcseconds (radius, 90% containment). This location is 52 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. No spectrum from the promptly downlinked event data is yet available to determine the column density. The initial flux in the 2.5 s image was 3.19e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 118 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 expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is J.D. Gropp (jdg44 AT 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.)
GCN 23270 table
GRB_name GRB180925A
GCN_number 23270
Detection_method Swift-XRT Other
ra 315.2038°
decl -64.4569°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23270 SUBJECT: GRB 180925A: Prompt enhanced Swift-XRT position DATE: 18/09/25 15:22:50 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 180925A, we find an enhanced XRT position of the afterglow: RA, Dec: 315.2038, -64.4569 which is equivalent to: RA (J2000) = 21 00 48.92 Dec (J2000) = -64 27 24.9 with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/863421. 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.
GCN 23271 table
GRB_name GRB180925A
GCN_number 23271
Detection_method Swift-XRT Det
ra 315.2008°
decl -64.4569°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23271 SUBJECT: GRB 180925A: Enhanced Swift-XRT position DATE: 18/09/25 22:20:42 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 1212 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180925A, 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 = 315.20075, -64.45690 which is equivalent to: RA (J2000): 21h 00m 48.18s Dec (J2000): -64d 27' 24.8" with an uncertainty of 3.8 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.
GCN 23272 table
GRB_name GRB180925A
GCN_number 23272
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 23272 SUBJECT: GRB 180925A: Swift-XRT refined Analysis DATE: 18/09/26 02:14:10 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 6.8 ks of XRT data for GRB 180925A (Gropp et al. GCN Circ. 23268), from 115 s to 19.2 ks after the BAT trigger. The data comprise 191 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 23270). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.1 (+/-0.4). At T+169 s the decay steepens to an alpha of 2.55 (+0.49, -0.22). The light curve breaks again at T+296 s to a decay with alpha=7.7 (+0.3, -1.3), and again at T+388 s s to alpha=0.71 (+0.26, -0.51), before a final break at T+1241 s s after which the decay index is 1.42 (+0.15, -0.13). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.42 (+/-0.08). The best-fitting absorption column is 1.4 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 3.3 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.77 (+/-0.17) and a best-fitting absorption column of 1.5 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.5 (+0.6, -0.5) x 10^21 cm^-2 Galactic foreground: 3.3 x 10^20 cm^-2 Excess significance: 3.7 sigma Photon index: 1.77 (+/-0.17) If the light curve continues to decay with a power-law decay index of 1.42, the count rate at T+24 hours will be 8.2 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.2 x 10^-14 (3.9 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00863421. This circular is an official product of the Swift-XRT team.
GCN 23273 table
GRB_name GRB180925A
GCN_number 23273
Detection_method Swift-BAT Det
ra 315.2120°
decl -64.4500°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23273 SUBJECT: GRB 180925A: Swift-BAT refined analysis DATE: 18/09/26 03:39:29 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU) (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 180925A (trigger #863421) (Gropp et al., GCN Circ. 23268). The BAT ground-calculated position is RA, Dec = 315.212, -64.450 deg which is RA(J2000) = 21h 00m 50.9s Dec(J2000) = -64d 26' 59.2" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T-5 s and ends at ~T+105 s. The main peak occurs at ~ T+1 s. T90 (15-350 keV) is 81.70 +- 23.25 sec (estimated error including systematics). The time-averaged spectrum from T-4.44 to T+103.96 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.13. The fluence in the 15-150 keV band is 4.1 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.87 sec in the 15-150 keV band is 3.1 +- 0.6 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/863421/BA/
GCN 23274 table
GRB_name GRB180925A
GCN_number 23274
Detection_method Swift-UVOT Det
ra 315.2029°
decl -64.4569°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23274 SUBJECT: GRB 180925A: Swift/UVOT Detection DATE: 18/09/26 12:53:04 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (UCL-MSSL) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180925A 119 s after the BAT trigger (Gropp et al., GCN Circ. 23268). A fading source consistent with the XRT position (Goad et al. GCN Circ. 23271) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 21:00:48.70 = 315.20292 (deg.) Dec (J2000) = -64:27:24.82 = -64.456894 (deg.) with an estimated uncertainty of 0.22 arc sec. (radius, 90% confidence), Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 119 269 147 19.73 +/- 0.17 white 557 6943 674 20.32 +/- 0.13 v 607 7354 549 >19.66 b 533 6739 347 20.89 +/- 0.37 u 277 6533 579 19.78 +/- 0.21 uvw1 657 7755 540 20.07 +/- 0.29 uvm2 1062 7559 413 >20.14 uvw2 583 7149 510 >20.60 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN 23275 table
GRB_name GRB180925A
GCN_number 23275
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 23275 SUBJECT: GRB 180925A: Insight-HXMT/HE detection DATE: 18/09/27 06:44:05 GMT FROM: Qi Luo at IHEP Q. Luo,Y. Huang,G. Li,S. L. Xiong,X. B. Li, C. K. Li, C.Z. Liu, X.F. Li, Z. W. Li, Z. Chang, J. L. Zhao, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU),F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2018-09-25T14:37:27.900 (T0), the Insight-HXMT/HE detected GRB 180925A(trigger ID: HEB180925609) in a routine search of the data, which was also triggered by Swift-BAT (Gropp et al.,GCN 23268). The Insight-HXMT/HE light curve mainly consists of a bright pulse with a duration (T90) of 23.23 s measured from T0-2.82 s. The 1-s peak rate, measured from T0+1.8640 s, is 1845.76 cnts/sec. The total counts from this burst is 10107.89 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB180925609_lc.jpg All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (record energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. The analysis results presented above are preliminary, final results will be published elsewhere. Insight-HXMT is the first Chinese space X-ray telescope, which was fundedjointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org.
GCN 23276 table
GRB_name GRB180925A
GCN_number 23276
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23276 SUBJECT: GRB 180925A: VLT optical observations DATE: 18/09/27 19:52:07 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst D. B. Malesani (DAWN/NBI and DARK/NBI), P. Schady (Univ. Bath), C. C. Thoene (HETH/IAA-CSIC), D. A. Kann (HETH/IAA-CSIC), and N. R. Tanvir (Univ. Leicester) report on behalf of the Stargate collaboration: We observed the optical counterpart of GRB 180925A (Gropp et al., GCN 23268; Emery & Gropp, GCN 23274) using the ESO VLT UT2 (Kueyen) equipped with the X-shooter instrument. A 60-seconds image in the SDSS r filter was taken with the acquisition camera, at approximate time 2018 September 26.17 UT (0.56 days after the GRB). At a location consistent with that of the UVOT afterglow (Emery & Gropp, GCN 23274), a faint source is marginally visible. Forced photometry, calibrated against nearby USNO-B1 stars, yields R = 22.9 +- 0.4 (Vega). No further observations are planned. We acknowledge support from the ESO staff at Paranal, in particular Joe Anderson and Jorge Lillo-Box.
GCN 23291 table
GRB_name GRB180925A
GCN_number 23291
Detection_method Konus-Wind Det
t_trigger 14:37:30.967 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 23291 SUBJECT: Konus-Wind observation of GRB 180925A DATE: 18/10/02 12:49:43 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 180925A (Swift-BAT detection: Gropp et al., GCN 23268; Ukwatta et al., GCN 23273; Insight-HXMT/HE observation: Luo et al., GCN 23275) triggered Konus-Wind at T0=52650.967 s UT (14:37:30.967). The burst light curve shows a multipeaked structure which starts at ~T0 and has a total duration of ~26 s. The emission is seen up to ~6 MeV. As observed by Konus-Wind, the burst had a fluence of 1.44(-0.23,+0.32)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+5.088 s, of 4.99(-1.51,+1.66)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 6 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.99(-0.17,+0.21) and Ep = 528(-135,+239) keV (chi2 = 77/76 dof). Fitting by a GRB (Band) model yields alpha = -0.84(-0.33,+0.40), Ep = 374(-139,+403) keV, and beta = -2.0(-8.0,+0.3) (chi2 = 77/75 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 6 MeV range by a power law with exponential cutoff model with alpha = -0.85(-0.20,+0.23) and Ep = 544(-125,+200) keV (chi2 = 93/76 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.8 (chi2 = 93/75 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180925_T52650/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN 23304 table
GRB_name GRB180925A
GCN_number 23304
Detection_method AstroSat CZTI
Circular_text TITLE: GCN CIRCULAR NUMBER: 23304 SUBJECT: GRB 180925A: Astrosat CZTI detection DATE: 18/10/03 18:03:54 GMT FROM: Vidushi Sharma at IUCAA V. Sharma and T. Khanam (IUCAA), V. Bhalerao (IIT-B), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a long GRB 180925A, which was also detected by Swift (Gropp J. D. et al., GCN 23268), Insight-HXMT/HE (Luo Q. et al., GCN 23275) and Konus-Wind (Kozlova A. et al., GCN 23291). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 14:37:33.5 UT. The measured peak count rate is 246 cts/s above the background in combined data of four quadrants, with a total of 2223 cts. The local mean background count rate was 506 cts/s. Using cumulative rates, we measure a T90 of around 34.7 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.