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

[vsnet-grb-info 38420] EP250508a: COLIBRÍ Optical Limit
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40391 SUBJECT: EP250508a: COLIBRÍ Optical Limit DATE: 25/05/08 07:01:07 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Noémie Globus (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), 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): We imaged the field of the EP250508a (ID: 01709175339; Liang et al. GCN Circ. 40390) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-05-08 06:15 to 06:34 UTC (from 0.2 to 0.5 hours after the trigger) and obtained 16 minutes of exposure in the i filter. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the WXT source position (Liang et al. GCN Circ. 40390) down to the following 3-sigma limit: i > 21.7 mag Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/40391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38419] EP250508a: Einstein Probe detection of an X-ray transient
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40390 SUBJECT: EP250508a: Einstein Probe detection of an X-ray transient DATE: 25/05/08 06:37:42 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.D. Liang, T. Zhao, H. Q. Cheng, W. D. Zhang (NAOC, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250508a. The transient triggered EP-WXT (ID: 01709175339) at 2025-05-08T06:03:47 (UTC). The WXT position of the source is R.A. = 178.266 deg, DEC = -19.900 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 178.2540 deg, DEC = -19.9225 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/40390. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38418] GRB 250507A: Swift-XRT refined Analysis
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40389 SUBJECT: GRB 250507A: Swift-XRT refined Analysis DATE: 25/05/07 22:02:18 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 1.8 ks of XRT data for GRB 250507A, from 7.4 ks to 12.5 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. We detect an uncatalogued X-ray source within the SVOM/ECLAIRs 90% C.L. error region (GCN #40374) at RA, Dec = 183.06416, -23.5888 which is equivalent to: RA (J2000): 12h 12m 15.40s Dec (J2000): -23d 35' 19.6" with an uncertainty of 4.2 arcsec (radius, 90% confidence). This position is 15.6 arcsec from the SVOM/MXT position (GCN #40381) and 2.5 arcsec from the source detected by EP-FXT (GCN #40385). The source has a mean count rate of 2.6e-02 ct/sec and a flux of 1.11 (+0.21, -0.20) × 10^-12 erg cm^-2 s^-1 (0.3-10 keV); we cannot determine at the present time whether it is fading. However, the decrease in flux compared to the SVOM/MXT observation suggests this source is the afterglow. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019769. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40389. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38417] IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40388 SUBJECT: IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/05/07 20:57:42 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-250506A (https://gcn.nasa.gov/circulars/40369) in a time range of 1000 seconds centered on the alert event time (2025-05-06 14:05:52.090 UTC to 2025-05-06 14:22:32.090 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-250506A. 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-250506A 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 6e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-05-05 14:14:12.090 UTC to 2025-05-07 14:14:12.090 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-250506A ranges from 1.6e-01 to 1.7e-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/40388. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38416] GRB 250506A: Swift/UVOT Upper Limits
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40387 SUBJECT: GRB 250506A: Swift/UVOT Upper Limits DATE: 25/05/07 20:04:42 GMT FROM: Samantha Oates at University of Birmingham <samantha.oates(a)alumni.ucl.ac.uk> S. R. Oates (Lancaster U.) and N. Klinger (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250506A 63 ks after the of the SVOM and Fermi-detected GRB 250506A (GCN Circs. 40355, 40358). No optical afterglow consistent with the SVOM MXT (Maggi et al., GCN Circ. 40364) and the XRT position (Burrows et al. GCN Circ. 40378) is detected in the initial UVOT exposures. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 64170 70154 1176 >22.1 v 64937 65102 163 >19.3 u 63403 69711 1530 >21.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40387. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38415] GRB 250427B : SVOM detection of a burst through offline search
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40386 SUBJECT: GRB 250427B : SVOM detection of a burst through offline search DATE: 25/05/07 16:58:28 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP), N. Dagoneau (CEA), O. Godet (IRAP), S.J. Zheng (IHEP), report on behalf of the SVOM team : The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250427B, starting at 2025-04-27T20:57:56.9 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station. The burst was detected by several methods and within several energy ranges and timescales. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.8 within 8-120 keV over a time window of 10.24 seconds starting at Tb. The lightcurve consists of a single pulse with a T90 of 11.0 +/-0.5 s in the 4-120 keV band. The localization of the source is RA, Dec = 208.380, 54.716 degrees: RA (J2000) = 13h53m31.2s Dec (J2000) = 54d42m57.6s with a 90% C.L. radius of 11.6 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright X-ray source are found in the error box. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM point of contact for this event is: Marius Brunet (IRAP) marius.brunet(a)irap.omp.eu. Please contact him 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/40386. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38414] GRB 250507A: follow-up observation with EP-FXT
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40385 SUBJECT: GRB 250507A: follow-up observation with EP-FXT DATE: 25/05/07 15:44:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. H. Zhang, H. Sun (NAO, CAS), Y. J. Zhang (THU), W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of GRB 250507A at 2025-05-07T07:33:50 (UTC), about 1 hour after the SVOM/ECLAIRs trigger (Wang et al., GCN # 40374). An uncatalogued X-ray source (EPF_J121215.7−233519) was detected within the ECLAIRs error circle, and is potentially associated with GRB 250507A. Preliminary analysis of this source was automatically conducted, with the following results: RA (J2000): 183.0647 deg Dec (J2000): -23.5883 deg Flux: 4.91 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV) Flux_error: 1.54 x 10^-13 erg/cm^2/s (1 sigma) The position uncertainty of the above source is about 10 arcsec in radius (90% C.L. statistical and systematic). We note that this source is spacially consistent with the one reported by SVOM/MXT (Maggi et al., GCN # 40381). The flux measured by EP-FXT shows a rapid decline of more than two orders of magnitude compared to the MXT measurements over a timescale of approximately 50 minutes, consistent with the rapid decay reported previously. 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/40385. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38413] GRB 250430A / EP250430a: AstroSat CZTI detection
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40384 SUBJECT: GRB 250430A / EP250430a: AstroSat CZTI detection DATE: 25/05/07 15:16:23 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 the long duration GRB 250430A which was also detected by Swift/BAT (Moss et al., GCN Circ. 40356), Konus/Wind (Svinkin et al., GCN Circ. 40367), and associated with the detection of EP250430a by EP/WXT (Wang et al., GCN Circ. 40299). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-30 17:31:00.84 UTC. The measured peak count rate associated with the burst is 279 (+66, -70) counts/s above the background in the combined data of all quadrants, with a total of 761 (+210, -232) counts. The local mean background count rate was 1336 (+7, -8) counts/s. We measure a T90 of 7.1 (+0.5, -2.5) s from the cumulative Veto light curve. 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/40384. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38412] EP#01709175213/IGR J19566+0326: Swift-XRT detection
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40383 SUBJECT: EP#01709175213/IGR J19566+0326: Swift-XRT detection DATE: 25/05/07 14:44:00 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> M.A. Williams (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: We have analyzed 1100 s of XRT data for the recently reported Einstein Probe (EP) trigger 01709175213 (GCN #40375), from T0+2.8 ks to T0+9.1 ks after detection by EP-WXT. The data are entirely in Photon Counting (PC) mode. We detect an X-ray source within the estimated 90% C.L. EP-WXT error region. Using 1135 s of XRT PC mode data and 2 UVOT images, we find an enhanced XRT position: RA, Dec = 299.16259, 3.44549 which is equivalent to: RA (J2000): 19h 56m 39.02s Dec (J2000): +03° 26′ 43.8′′ with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position is 46 arcsec from the EP-WXT position, and consistent with the X-ray source found in EP-FXT data. As noted by Sun et al. (GCN #40375), this position is consistent with the LMXB IGR J19566+0326/MAXI J1957+032. The source has a peak count rate of 14.76 (±0.23) ct/s (0.3-10 keV). The mean count rate from the LSXPS catalogue is 0.1240 (±0.0019) ct/s, suggesting this source is an outburst of IGR J19566+0326. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/EP/EP_FIELD00037/. View this GCN Circular online at https://gcn.nasa.gov/circulars/40383. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38411] GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 07 May '25

07 May '25

TITLE: GCN CIRCULAR NUMBER: 40382 SUBJECT: GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/05/07 14:39:13 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), 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), Antonio de Ugarte Postigo (LAM), Chenwei WANG (IHEP) and Lin LAN (NAOC): We imaged the field of the SVOM GRB 250506A (Wang et al., GCN Circ. 40358) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-05-07T03:44:16 to 05:14:17 UTC (from 1.12 to 1.22 days after the trigger) and obtained 64 minutes of exposure in the i filter. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the improved MXT position (Maggi et al., GCN Circ. 40364) and at the XRT position (Burrows et al., GCN Circ. 40378) down to the following 5-sigma limit (AB): i > 22.4 This upper limit is consistent with the one reported by Xin et al. (GCN Circ. 40366), Ferro et al. (GCN Circ. 40363), Liu et al. (GCN Circ. 40360), Postigo et al. (GCN Circ. 40359), and Liu et al. (GCN Circ. 40373). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/40382. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0