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

[vsnet-grb-info 38036] GRB 250402B: AstroSat CZTI detection of a short burst
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40016 SUBJECT: GRB 250402B: AstroSat CZTI detection of a short burst DATE: 25/04/03 04:52:18 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short duration GRB 250402B. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-02 09:13:57.65 UTC. The measured peak count rate associated with the burst is 288 (+164, -12) counts/s above the background in the combined data of three quadrants (out of four), with a total of 218 (+50, -53) counts. The local mean background count rate was 292 (+10, -12) counts/s. Using cumulative rates, we measure a T90 of 0.93 (+0.11, -0.23) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The measured peak count rate associated with the burst is 360 (+65, -74) counts/s above the background in the combined data of all the four quadrants with a total of 457 (+202, -244) counts. The local mean background rate was 1317 (+8, -7) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40016. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38035] GRB 250402A: SVOM/VT optical counterpart
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40015 SUBJECT: GRB 250402A: SVOM/VT optical counterpart DATE: 25/04/03 00:26:36 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L.P. Xin, Y. L. Qiu, C. Wu, H. L. Li, J . Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, Y. N. Yi, J. Y. Wei (NAOC), J. T. Palmerio(CEA/Irfu), T. Sadibekova(CEA) report on behalf of the SVOM team: SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Chen et al., GCN 40014). SVOM/VT began observing the field automatically with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With VHF downlinked data, a bright uncatalogued source was found in both channels in the first sequence, and brightening with about 0.2 mag in the second sequence, compared to DESI catalog. The coordinates are RA, Dec = 213.40915, -5.93013 which is equivalent to: R.A.(J2000) = 14:13:38.20, DEC.(J2000)= -05:55:48.5 Error=0.5 arcseconds. The brightness are VT_B ~21.53 mag(AB) and VT_R ~20.61 mag(AB) in the first sequence with the mid time of 443 seconds after the burst. We proposed that this is the optical counterpart of the burst. Given the VT color, it is likely a low/medium redshift burst. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/40015. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38034] GRB 250402A: SVOM detection of a burst
by GCN Circulars 03 Apr '25

03 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40014 SUBJECT: GRB 250402A: SVOM detection of a burst DATE: 25/04/03 00:15:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> X. Chen(YNU), Y. Hu(GXU), H. Yang(IRAP), B. Cordier (CEA), L. Zhang(IHEP), P. Maggi (ObAS) on behalf of the SVOM mission team. At 2025-04-02T23:07:56 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250402A (SVOM burst-id sb25040203). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 15 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 27.79 in the [8-120] keV energy band over a time window of 40.96 seconds starting at Tb. The light curve showed a long GRB with a T90 duration of about 35 (+/-3) s. The localization of the best alert is R.A., Dec 213.3783, -5.9457 degrees (J2000) with a 90% C.L. radius of 3.42 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. MXT began observing the field at 2025-04-02T23:10:58 UTC, 183 seconds after Tb. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec 213.3893, -5.9468 degrees: RA (J2000) = 14h13m33.44s DEC (J2000) = -5d56m48.59s with a 90% C.L. radius of 45 arcseconds(including 25 arcseconds systematic error added in quadrature). This location is 0.66 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is X. Chen: xlchen(a)stu.ynu.edu.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40014. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38033] GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40013 SUBJECT: GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit DATE: 25/04/02 20:48:13 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We imaged the field of GRB 250331C detected by Swift Burst Alert Telescope (BAT) (Cenko et al. GCN 39959), with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-03-31 20:59 UT (approximately 16.37 hours after burst) stacking a set of unfiltered CCD image. The observations were made with modest sky conditions and the target low on the horizon. We co-added 30 exposures of 60 sec each. Start T0+ End T0+ CR lim 16.37 hour 16.92 hour 18.7 We did not found any optical counterpart in the error box of the XRTcandidate. Evans GCN 39960 Magnitudes were estimated with the PanSTARRS cat. and are not corrected for galactic dust extinction. Our observations are consistent with other already reported Dornic et al. (GCN 39963), Lipunov et al. (GCN 39981), Siegel et al. (GCN 40003). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40013. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38032] GRB 250314A: ALMA detection
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40012 SUBJECT: GRB 250314A: ALMA detection DATE: 25/04/02 20:20:24 GMT FROM: Tanmoy Laskar at U of Utah <tanmoylaskar(a)gmail.com> T. Laskar (University of Utah), R. Margutti, R. Chornock, Nayana A. J. (UC Berkeley), K. D. Alexander (University of Arizona), and H. Sears (Rutgers University) report: “We observed the high-redshift (z ~ 7.3; Malesani et al., GCN 39732; Rakotondrainibe et al., GCN 39743) SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719) with the Atacama Large Millimeter/Submillimeter Array (ALMA) beginning on 2025 March 26 02:55 UTC (11.6 days after the burst) at multiple frequencies. Preliminary analysis reveals a mm source with flux density of ~ 40 microJy at 42 GHz at position: RA (J2000) = 13:25:12.14 Dec (J2000) = -05:16:55.29 with an uncertainty of 0.18" in each coordinate. This is consistent with the optical position (Malesani et al., GCN 39727) and radio position (Nayana A. J. et al., GCN 39954). We note that GRBs 250314A and 090423 (z ~ 8.2; Tanvir et al., Nature, 461, 7268, 1254; Castro Tirado et al., GCN 9273; de Ugarte Postigo et al., A&A, 538, A44, 2012) are the highest-redshift GRBs with mm-band detections so far. Further ALMA observations are planned. We thank the ALMA Director for rapidly granting our DDT request and the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations." View this GCN Circular online at https://gcn.nasa.gov/circulars/40012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38031] GRB 250329B: Swift/UVOT Upper Limit
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40011 SUBJECT: GRB 250329B: Swift/UVOT Upper Limit DATE: 25/04/02 15:39:59 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M.H. Siegel (PSU) and R. Caputo (GSFC) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250329B 7.4 ks after the SVOM trigger sb25032902 (Xie et al., GCN Circ. 39925). We do not detect an afterglow at the position of the XRT counterpart (Beardmore et al., GCN Circ. 39939). Preliminary detections and 3-sigma upper limits for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag(AB) u 7392 8531 1121 >21.00 u 92986 110466 2225 >20.80 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40011. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38030] GRB 250329A: Swift/UVOT Upper Limit
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40010 SUBJECT: GRB 250329A: Swift/UVOT Upper Limit DATE: 25/04/02 15:12:53 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M.H. Siegel (PSU) and R. Caputo (GSFC) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250329A 6.8ks after the SVOM trigger sb25032901 (Wang et al., GCN Circ. 39916). We do not detect an afterglow at the position of the XRT counterpart (Dichiara et al., GCN Circ. 39924) or optical-infrared counterparts (Watson et al., GCN Circ. 39915; Want et al., GCN Circ. 39917; Ghosh et al., GCN Circ. 39922). The lack of detection in the u-band for this bright burst would be consistent with the redshift of z=2.9 reported by Schneider et al. (GCN Circ. 39918). Preliminary detections and 3-sigma upper limits for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag(AB) u 6812 13135 1551 >20.95 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.021 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40010. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38029] GRB 250327B: Swift/UVOT Detection
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40009 SUBJECT: GRB 250327B: Swift/UVOT Detection DATE: 25/04/02 13:32:05 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M.H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250327B 1753 s after the SVOM trigger sb25032706 (GCN Circ. 39888). A fading source consistent with the XRT position (Page et al., GCN Circ. 39895) and the optical counterpart (Moskvitin et al., GCN Circ. 39889; Xin et al., GCN Circ. 39890; O’Neill et al., GCN Circ. 39891; Lian et al., GCN Circ. 39894; Shrestha et al., GCN Circ. 39896; Ducoin et al., GCN Circ. 39897; Perley & Bochenek; GCN Circ. 39902; Kumar et al., GCN Circ. 39904; Dennefeld et al., GCN circ. 39905; Pankov et al., GCN circ. 39906) is detected in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag(AB) u 1753 2505 740 19.78+/-0.18 u 91894 113326 2601 >21.28 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.018 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38028] GRB 250327A: Swift/UVOT Upper Limits
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40008 SUBJECT: GRB 250327A: Swift/UVOT Upper Limits DATE: 25/04/02 13:08:08 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) and T. M. Parsotan (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250327A 13.8 ks after the BAT trigger (Parsotan et al., GCN Circ. 39877). No optical afterglow consistent with the XRT position (Burrows et al., GCN Circ. 39892) GCN Circ. 39977) 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 B 25500 43748 1714 >20.88 UVM2 47869 48769 885 >20.28 U 14704 42891 1711 >20.58 V 21282 21402 117 >18.30 UVW1 13797 49176 1885 >20.62 UVW2 20376 21275 885 >20.31 WHITE 26413 27065 633 >20.81 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.053 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40008. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38027] GRB 250331E: SVOM/GRM observation
by GCN Circulars 02 Apr '25

02 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40007 SUBJECT: GRB 250331E: SVOM/GRM observation DATE: 25/04/02 08:09:11 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Frédéric Piron (LUPM), Nicolas Dagoneau (CEA) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250331E (SVOM trigger reference: sb25033103) at 2025-03-31T22:46:35.000 (T0). This burst was also detected by Fermi/GBM (Fermi GBM Team, GCN 39988). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of single main pulse with a T90 of 12.0 +1.0/-2.0 s in the 15-5000 keV band. In addition, ECLAIRs was taking data and did not trigger, since the position of this burst, as determined by Fermi/GBM (GCN 39988, RA: 196.6 deg, DEC: -27.7 deg, Error: 14.0 deg), is located at about 60.7 degrees from the SVOM optical axis, and outside the ECLAIRs field of view. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250331E.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: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40007. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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