April 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 38146] IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40122 SUBJECT: IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/04/08 19:18:55 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250406A (https://gcn.nasa.gov/circulars/40103) in a time range of 1000 seconds centered on the alert event time (2025-04-06 22:42:15.340 UTC to 2025-04-06 22:58:55.340 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-250406A. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250406A is 1.4e-01 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 9e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-04-05 22:50:35.340 UTC to 2025-04-07 22:50:35.340 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-250406A is 1.6e-01 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/40122. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38145] Konus-Wind detection of GRB 250407A
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40121 SUBJECT: Konus-Wind detection of GRB 250407A DATE: 25/04/08 16:13:31 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250407A ( Fermi-GBM detection: The Fermi GBM team, GCN 40104; Mukherjee & Meegan, GCN 40114; SVOM/GRM observation: Wang et al., GCN 20120) triggered Konus-Wind (KW) at T0=56895.249 s UT (15:48:15.249). The burst afterglow was detected and localized by SRG/ART-XC (Molkov et al. 2025, GCN 40110) and Swift-XRT (Dichiara et al. 2025, GCN 40113). The burst light curve shows a bright pulse which starts at ~T0-6 s and has a total duration of ~20 s. A weaker emission can be traced at least to ~T0+50 s. The emission in the main pulse is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250407_T56895/ As observed by Konus-Wind, the burst had a fluence of (1.57 ± 0.04)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 5.292 s, of (1.41 ± 0.05)x10^-4 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+15.616 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.02 (-0.03,+0.03), the high energy photon index beta = -2.27 (-0.07,+0.06), the peak energy Ep = 648 (-44,+46) keV, chi2 = 162/97 dof. The spectrum near the peak count rate (measured from T0+5.888 s to T0+7.424 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.76 (-0.06,+0.07), the high energy photon index beta = -2.38 (-0.14,+0.11), the peak energy Ep = 833 (-99,+106) keV, chi2 = 78/65 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40121. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38144] GRB 250407A: SVOM/GRM observation of a bright long burst
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40120 SUBJECT: GRB 250407A: SVOM/GRM observation of a bright long burst DATE: 25/04/08 14:40:37 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Marius Brunet, Jean-Luc Atteia, Hui Yang (IRAP), Maria-Grazia Bernardini (INAF-OAB), Stéphane Schanne (CEA), Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250407A (SVOM trigger reference: sb25040701) at 2025-04-07T15:48:13.000 (T0). This burst was also detected by Fermi/GBM (Fermi GBM Team, GCN 40104). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 11.1 +0.2/-0.3 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250407A.png In addition, ECLAIRs onboard trigger also detected a very significant increase of the count-rates at the time of the burst, but the detector plane image is not correlated with the mask pattern. This confirmed that the position of this burst, which is determined by Swift/XRT (GCN 40113, RA: 110.75876 deg, DEC: 36.79827 deg, Error: 2.8 arcsec), located at about 45.6 degrees from the SVOM optical axis, and was just outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0 to T0+18 s is best fitted by Band function. The alpha is -0.90 +/- 0.01, beta is -2.27 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 569 +/- 27 keV. The event fluence (10-1000 keV) in this time interval is (1.08 +/- 0.01)E-04 erg/cm^2. Thus GRB 250407A is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250407A_amati.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38143] GRB 250407A: EP-WXT afterglow detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40119 SUBJECT: GRB 250407A: EP-WXT afterglow detection DATE: 25/04/08 09:47:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. C. Zheng, D. F. Hu (PMO, CAS), X. Mao, W. X. Wang, W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of the X-ray afterglow of GRB 250407A by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. In an observation starting at 2025-04-07T17:11:31.158 (UTC), WXT detected an uncatalogued X-ray source at a position R.A. = 110.767 deg, DEC = 36.800 deg (J2000) with an uncertainty of 2.7 arcmin (radius, 90% C.L. statistical and systematic). This source is only 25 arcsec away from the X-ray afterglow of GRB 250407A that was detected by Swift/XRT (GCN 40113). The WXT observation started about 83 minutes after the trigger of GRB 250407A by Fermi/GBM (GCN 40104). The temporal and spatial coincidence suggests that WXT likely detected the X-ray afterglow of GRB 250407A. The observation lasted for 422 seconds, during which no significant variation was observed. The time-averaged spectrum can be fitted with an absorbed powerlaw model, with a photon index of 1.5(-0.7/+0.8), while nH is fixed at the Galactic value of 7.1 x 10^20 cm^-2. The unabsorbed 0.5-4 keV flux is estimated to be 2.0 (-0.7/+1.2) x 10^-10 erg/s/cm^2. The uncertainties are quoted at the 90% confidence level for the above spectral parameters. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38142] EP250407a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40118 SUBJECT: EP250407a: EP-WXT detection of a fast X-ray transient DATE: 25/04/08 09:13:36 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu, T. C. Zheng (PMO, CAS), X. Mao, W. X. Wang, W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient EP250407a detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient started at 2025-04-07T23:27:23 (UTC) and lasted for about 70s. We apologize that an incorrect trigger date was reported in the GCN Notice (trigger ID: 11916648441). The WXT position of EP250407a is R.A.= 134.813 deg, DEC = -38.956 deg (J2000) with an uncertainty of 2.5 arcmin (radius, 90% C.L. statistical and systematic). No known X-ray sources are found within the WXT error circle. The average 0.5-4 keV spectrum can be fitted with an absorbed powerlaw with a photon index of 1.4 (+/-0.6) and a fixed Galactic hydrogen column density of 4.67 x 10^21 cm^-2. We derive an average unabsorbed flux of 4.7(-1.0/+1.2) x 10^(-9) erg/s/cm^2, and a peak flux of approximately 1.0 x 10^(-8) erg/s/cm^2 (both in 0.5-4 keV). A follow-up observation with the Follow-up X-ray Telescope (FXT) on board the EP is planned. Further follow-up observations are encouraged to identify the nature of this X-ray transient. The contact TA of this source is Ding-Fang Hu, please contact him via the email dfhu(a)pmo.ac.cn if needed. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/40118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38141] GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40117 SUBJECT: GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart DATE: 25/04/08 08:55:29 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (U Roma), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of GRB 250407A (Fermi GBM team, GCN Circ. 40104; Preis et al., GCN Circ. 40105) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-08 UTC. We observed from 03:01 to 03:53 UTC (11.21 to 12.09 hours after the trigger) and obtained 20 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. At the position reported previously by SRG/ART-XC (Molkov et al. GCN Circ. 40110) and Swift/XRT (Evans et al., GCN Circ. 40113), we detect a source with a magnitude of i = 19.96 +/- 0.03, consistent with the value reported by Zheng et al. (GCN Circ. 40116). In this position, there is a previously identified source (ID: 152151107588088917) in the Pan-STARRS catalog with a PSF magnitude of i = 22.99 +/- 0.14. We propose that this is the host galaxy of GRB 250407A. Further observations are planned. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38140] GRB 250407A: KAIT Optical Afterglow Candidate
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40116 SUBJECT: GRB 250407A: KAIT Optical Afterglow Candidate DATE: 25/04/08 05:41:09 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> 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, observed the field of GRB 250407A (GBM team, GCN 40104; Preis et al., GCN 40105; Mukherjee et al., GCN 40114) around the X-ray afterglow location (Molkov et al., GCN 40110; Dichiara et al., GCN 40113) starting at 04:17, Apr. 08 UT, about 12.48 hours after the burst. A set of clear (roughly R) filter images were obtained. Within the XRT afterglow (Dichiara et al., GCN 40113) error circle, we detected an uncataloged optical afterglow candidate at J2000 position of (error ~0.5"): RA: 07:23:02.11 Dec: +36:47:54.97 We estimate the clear band magnitude to be ~20.1 +/- 0.3 mag (Vega) at 12.48 hours after the burst. Further observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/40116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38139] IceCube-250406A: No candidates from the Zwicky Transient Facility
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40115 SUBJECT: IceCube-250406A: No candidates from the Zwicky Transient Facility DATE: 25/04/08 01:35:32 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Jannis Necker (DESY), Akshay Eranhalodi (DESY), Robert Stein (JSI), Anna Franckowiak (Ruhr University Bochum) and Jesper Sollerman (Stockholm) report: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-250406A (Zegarelli et. al, GCN 40103) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2025-04-07 03:54 UTC, approximately 5.1 hours after event time. We covered 69.0% (0.6 sq deg) of the reported localization region. This includes 10.1% (0.1 sq deg) at galactic latitude < 10 deg. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). No candidate counterparts were detected. This is consistent with non-detections reported by other optical telescopes (Becerra et al, GCN 40101, 40102, 40108). Observations of this field will continue as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/40115. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38138] GRB 250407A: Fermi GBM Detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40114 SUBJECT: GRB 250407A: Fermi GBM Detection DATE: 25/04/08 01:28:16 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 15:48:21.07 UT on 07 April 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250407A (trigger 765733706/250407659). The afterglow was detected by ART-XC (Molkov et al. 2025, GCN 40110) and Swift-XRT (Dichiara et al. 2025, GCN 40113). The Fermi GBM Final Localization (GCN 40104) is consistent with the ART-XC and Swift-XRT positions. The angle from the Fermi LAT boresight is 116 degrees. The GBM light curve consists of a single-peak emission episode with a duration (T90) of about 6.3 s (50-300 keV). The time-averaged spectrum from T0+0.6 to T0+5.1 s is best fit by a Band function with Epeak = 470 +/- 20 keV, alpha = -0.18 +/- 0.03, and beta = -2.08 +/- 0.03. The event fluence (10-1000 keV) in this time interval is (2.65 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 62.4 +/- 0.7 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40114. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38137] GRB 250407A: Swift-XRT afterglow detection
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40113 SUBJECT: GRB 250407A: Swift-XRT afterglow detection DATE: 25/04/08 00:14:46 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250407A (GCN circ. 40104, GCN circ. 40105). We searched for X-ray sources in 293 s of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 293 s, obtained between T0+18.8 ks and T0+19.1 ks. An uncatalogued X-ray source is detected within the estimated 3-sigma Fermi/GBM error region (29 arcsec) and is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 293 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 110.75876, +36.79827 which is equivalent to: RA (J2000): 07h 23m 02.10s Dec(J2000): +36d 47' 53.8" with an uncertainty of 2.8 arcsec (radius, 90% confidence). This position is 6.9 arcsec from the SRG/ART-XC position reported by Molkov et al (GCN circ. 40110). We note that the source has faded since the SRG/ART-XC observation. A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.8 (+0.4, -0.3). The best-fitting absorption column is 3.0 (+1.7, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 7.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.0 (+1.7, -1.4) x 10^21 cm^-2 Galactic foreground: 7.0 x 10^20 cm^-2 Excess significance: 2.8 sigma Photon index: 1.8 (+0.4, -0.3) The results of the XRT-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/ToO_GRBs/00021826/Source1.php. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021826. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40113. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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