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

[vsnet-grb-info 38430] EP250508a: KAIT optical upper limit
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40401 SUBJECT: EP250508a: KAIT optical upper limit DATE: 25/05/08 18:38:55 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) 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 EP250508a (Liang et al., GCN 40390) starting at 06:17, May 08 UT, about 14 minutes after the burst. A set of clear (roughly R) filter images were obtained. Preliminary analysis do not reveal any new optical counterpart candidate within the X-ray afterglow error circles (Liang et al., GCN 40390; Zhao et al., GCN 40399). Due to the bright moonlight, our image quality are degraded and we estimate the limiting magnitude of our single image to be ~17.0 mag, shallower than the upper limit reported by other groups (Ugarte Postigo et al., GCN 40391; Lipunov et al., GCN 40393; Brivio et al., GCN 40395). View this GCN Circular online at https://gcn.nasa.gov/circulars/40401. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38429] GRB 250507A: KAIT optical upper limit
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40400 SUBJECT: GRB 250507A: KAIT optical upper limit DATE: 25/05/08 18:37:31 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) 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 SVOM GRB 250507A (Wang et al., GCN 40374) starting at 06:37:30, May 07 UT, 165 seconds after the burst. Observations were performed in 3 x 3 tiling mode, and a set of clear (roughly R) filter images were obtained. Preliminary analysis do not reveal any new optical counterpart candidate within the X-ray afterglow error circles (Maggi et al., GCN 40381; Zhang et al., GCN 40385; Osborne et al., GCN 40389), neither in single image, nor in the co-add images. We estimate the limiting magnitude of our coadd image to be ~20.0 mag at a mid-time of 15.0 minutes after the burst, consistent with the upper limit reported by other groups (Ducoin et al., GCN 40376; Xin et al., GCN 40379; Brivio et al., GCN 40380) View this GCN Circular online at https://gcn.nasa.gov/circulars/40400. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38428] EP250508a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40399 SUBJECT: EP250508a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/05/08 16:08:00 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T.Zhao, R. D. Liang, H. Q. Cheng, W. D. Zhang (NAOC, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP250508a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Liang et al., GCN 40390), and followed up by several telescopes (Antonio et al, GCN 40391; Lipunov et al, GCN 40393; Brivio et al, GCN 40395). Refined analysis of the WXT data shows that the event started at T0=2025-05-08T06:02:28.850 (UTC) and lasted for about 60 s before the observation was interrupted by the autonomous follow-up observation. The peak flux is about 3.6 x 10^(-9) erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted by an absorbed power law model with a Galactic hydrogen column density of 3.56 x 10^20 cm^-2 and a photon index of 0.91 (+/-0.54). The derived average unabsorbed 0.5-4 keV flux is 1.4 (-0.4/+0.5) x 10^(-9) erg/s/cm^2. The uncertainties are quoted at the 90% confidence level for the above parameters. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 3 min after T0, starting at 2025-05-08T06:05:21 (UTC). Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 178.2555, DEC = -19.9244 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). During the observation a decline in the source flux lasting for a few hundred seconds is observed from the beginning. The averaged 0.5-10 keV FXT spectrum can be fitted by an absorbed power law model with a Galactic hydrogen column density of 3.56 x 10^20 cm^-2 and a photon index of 2.30 (-0.45/+0.45). The derived average unabsorbed 0.5-10 keV flux is 2.0 (-0.5/+0.8) x 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. EP-FXT will continue monitoring this source. More follow-up observations are encouraged. The contact TA of EP250508a is R. D. Liang. Please contact him via email liangrd(a)bao.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/40399. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38427] GRB 250505B: SVOM/GRM observation of a short burst
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40398 SUBJECT: GRB 250505B: SVOM/GRM observation of a short burst DATE: 25/05/08 15:29:40 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Hui Yang, Laurent Bouchet (IRAP), Frédéric Piron (LUPM), Stéphane Schanne (CEA) report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short burst GRB 250505A at 2025-05-05T02:10:34 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike followed by a tail with a T90 of 0.26 +0.13/-0.07 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250505A.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 55.6 deg DEC: -39.0 deg Error: 4.6 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 95 degrees from the SVOM optical axis. ECLAIRs was in operation during the burst but no significant signal is detected, which confirms that the burst occurred outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0+0.02 to T0+0.15 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.10 +0.37/-0.35 and the cutoff energy, parameterized as Epeak, is 70 +/-10 keV. The event fluence (10-1000 keV) in this time interval is (5.9 +0.6/-0.5)E-07 erg/cm^2. The localization of GRB 250505A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/grb250505A_amati.png We note that the Epeak of this burst is relatively soft in short GRBs, while the hardness and duration are both similar to a magnetar X-ray 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM 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/40398. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38426] GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40397 SUBJECT: GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation. DATE: 25/05/08 14:26:33 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 observed the field of GRB 250502A detected by SVOM/ECLAIRs (Wang et al. GCN 40313) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-05-02 21:24 UT (approximately 12.62 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and good visibility conditions. We detected a very faint object at the following position: RA (J2000.0) 13h 46m 05.62s Decl. (J2000.0) -10° 45' 32.3" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Mag. err. 2025-05-02 23:44:41 UT 14.97 200x60s CR 20.70 +/-0.16 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Rakotondrainibe et al. GCN 40315; An et al. GCN 40319; Li et al. GCN 40320; Ghosh et al. GCN 40322; de Ugarte Postigo et al. GCN 40328; Pérez-Fournon et al. GCN 40330; Odeh et al. GCN 40331; Bochenek & Perley GCN 40333; Corcoran et al. GCN 40334; Leonini et al. GCN 40337; Zheng et al. GCN 40338; Pankov et al. GCN 40339; Brivio et al. GCN 40349; Quadri et al. GCN 40370. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40397. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38425] GRB 250506A: GECAM detection
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40396 SUBJECT: GRB 250506A: GECAM detection DATE: 25/05/08 14:13:56 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 250506A at 2025-05-06T02:23:22.850 UTC (denoted as T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #40355) and SVOM (Wang et al., GCN #40358). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 34.6 +0.8/-1.9 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250506A.png With the localization of RA, Dec = 219.28269, +28.87835, as determined by Swift/XRT (D.N. Burrows et al., GCN #40394), the time-averaged spectrum from T0-10s to T0+60 s is best fitted by a powerlaw with an alpha of -2.02 +/- 0.11. The event fluence (10-1000 keV) in this time interval is (2.60 +/- 0.14)E-05 erg/cm^2. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/40396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38424] EP250508a: REM optical/NIR observations
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40395 SUBJECT: EP250508a: REM optical/NIR observations DATE: 25/05/08 10:22:35 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB EP250508a detected by EP/WXT (Liang et al., GCN 40390) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 May 08 at 06:12:51 UT (i.e. about 9 minutes after the burst), and lasted for about 2 hours. From preliminary inspection, we do not detect any possible counterpart inside the EP/FXT error circle down to the following 3sigma limits: r > 19.2 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 51 minutes after the trigger; H > 16.0 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 57 minutes after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40395. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38423] GRB 250506A: Swift-XRT afterglow detection
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40394 SUBJECT: GRB 250506A: Swift-XRT afterglow detection DATE: 25/05/08 08:42:38 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has conducted further observations of the field of the SVOM/MXT-detected burst GRB 250506A. The observations now extend from T0+63.4 ks to T0+138.3 ks and have a total exposure time of 6.3 ks. The source previously reported, "Source 1", is fading with 2.8 sigma significance and thus is believed to be the GRB afterglow. Using 2772 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 219.28269, +28.87835 which is equivalent to: RA (J2000): 14h 37m 07.85s Dec(J2000): +28d 52' 42.0" with an uncertainty of 2.6 arcsec (radius, 90% confidence). This position is 84 arcsec from the SVOM/MXT position. The light curve can be modelled with a power-law decay with a decay index of alpha=1.7 (+0.5, -0.4). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.74 (+0.34, -0.21). The best-fitting absorption column is 2.1 (+7.8, -0.4) x 10^20 cm^-2, consistent with the Galactic value of 1.6 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 3.8 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.1 (+7.8, -0.4) x 10^20 cm^-2 Galactic foreground: 1.6 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.74 (+0.34, -0.21) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021828. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021828. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40394. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38422] EP250508a: Global MASTER-Net observations report
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40393 SUBJECT: EP250508a: Global MASTER-Net observations report DATE: 25/05/08 07:27:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250508a ( EP Team et al., GCN 40390) errorbox 2079 sec after notice time and 4289 sec after trigger time at 2025-05-08 07:15:16 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 78 deg. The sun altitude is -50.3 deg. The galactic latitude b = 41 deg., longitude l = 286 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2865106 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4319 | 2025-05-08 07:15:16 | MASTER-OAFA | (11h 53m 09.22s , -19d 33m 11.7s) | C | 60 | 17.4 | 4394 | 2025-05-08 07:16:31 | MASTER-OAFA | (11h 53m 07.05s , -19d 31m 34.0s) | C | 60 | 17.4 | 4470 | 2025-05-08 07:17:47 | MASTER-OAFA | (11h 53m 07.04s , -19d 33m 09.7s) | C | 60 | 17.3 | 4546 | 2025-05-08 07:19:02 | MASTER-OAFA | (11h 53m 09.55s , -19d 31m 44.2s) | C | 60 | 17.2 | 4623 | 2025-05-08 07:20:19 | MASTER-OAFA | (11h 53m 03.85s , -19d 32m 19.3s) | C | 60 | 17.1 | 4698 | 2025-05-08 07:21:35 | MASTER-OAFA | (11h 53m 04.97s , -19d 31m 19.3s) | C | 60 | 17.1 | 4774 | 2025-05-08 07:22:50 | MASTER-OAFA | (11h 53m 10.78s , -19d 32m 20.0s) | C | 60 | 17.1 | 4851 | 2025-05-08 07:24:07 | MASTER-OAFA | (11h 53m 03.30s , -19d 33m 20.6s) | C | 60 | 17.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40393. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38421] GRB 250506A: SVOM/VT optical upper limit
by GCN Circulars 08 May '25

08 May '25

TITLE: GCN CIRCULAR NUMBER: 40392 SUBJECT: GRB 250506A: SVOM/VT optical upper limit DATE: 25/05/08 07:22:50 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> L. Lan(NAOC), C. W. Wang(IHEP), R. C. Chen(NJU), W. J. Tan(IHEP), L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA) report on behalf of the SVOM mission team. After the trigger by SVOM/ECLAIRs and Fermi/GBM at 2025-05-06T02:23:22 UTC (SVOM burst-id sb25050601, Fermi burst-id bn250506100), VT performed ToO observations on the burst in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The observation started at 13.69 hours after the SVOM trigger. No uncataloged sources are detected in single or stacked images within the errorbox of Eclairs or MXT (Maggi et al., GCN 40364), compared to the Legacy survey. The 3 sigma upper limits are derived below: Mid_time | Band | Exposure Time (second) | Upper limit (AB) 15.64 hour | VT_B | 100*63 | 23.7 15.64 hour | VT_R | 100*73 | 23.6 This results are consistent with the report (de Ugarte Postigo et al. GCN 40359). 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/40392. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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