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

[vsnet-grb-info 38316] SVOM/sb25043004: SVOM detection of a X-ray transient
by GCN Circulars 30 Apr '25

30 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40287 SUBJECT: SVOM/sb25043004: SVOM detection of a X-ray transient DATE: 25/04/30 11:39:06 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y. Liang (PMO), W. Zheng (Berkeley), O. Godet, S. Guillot (IRAP), C. Plasse, J. T. Palmerio (CEA) on behalf of the SVOM mission team. SVOM/ECLAIRs triggered and located the X-ray transient sb25043004 (SVOM burst-id sb25043004) starting at 2025-04-30T10:40:57.1 UTC (Tb). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The source was only detected by the Image Trigger (IMT), which produced a sequence of 3 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 8.96 in the [5-8] keV energy band over a time window of 327.68 seconds starting at Tb. The localization of the best alert is R.A., Dec. 272.104, -38.6635 degrees: R.A. (J2000) = 18h08m25.13s Dec. (J2000) = -38d39m48.60s with a 90% confidence level (C.L.) radius of 8.82 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the source. MXT 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. 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 Weikang Zheng: weikang(a)berkeley.edu. 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/40287. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38315] Fermi trigger No 767623859: Global MASTER-Net observations report
by GCN Circulars 30 Apr '25

30 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40286 SUBJECT: Fermi trigger No 767623859: Global MASTER-Net observations report DATE: 25/04/30 09:31:00 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) started inspect of the Fermi GRB250429.54 (trigger No 767623859,22h 03m 43.92s , -05d 28m 01.2s, R=31.13) errorbox 73850 sec after notice time and 73884 sec after trigger time at 2025-04-30 09:22:19 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 42 deg. The sun altitude is -22.3 deg. The galactic latitude b = -45 deg., longitude l = 55 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2856527 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 73905 | 2025-04-30 09:22:19 | MASTER-OAFA | (21h 58m 38.65s , -10d 46m 32.6s) | C | 40 | 17.6 | 73915 | 2025-04-30 09:22:19 | MASTER-OAFA | (22h 07m 54.27s , -10d 23m 06.7s) | C | 60 | 19.2 | 73983 | 2025-04-30 09:23:37 | MASTER-OAFA | (22h 01m 48.50s , -14d 36m 44.5s) | C | 40 | 17.8 | 73993 | 2025-04-30 09:23:37 | MASTER-OAFA | (22h 11m 12.61s , -14d 13m 10.4s) | C | 60 | 19.5 | 74058 | 2025-04-30 09:24:53 | MASTER-OAFA | (22h 13m 36.90s , -16d 29m 55.1s) | C | 40 | 18.0 | 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/40286. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38314] EP250428b: refined analysis of the EP-FXT follow-up observation
by GCN Circulars 30 Apr '25

30 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40285 SUBJECT: EP250428b: refined analysis of the EP-FXT follow-up observation DATE: 25/04/30 09:16:55 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. Y. Wu, M. J. Liu, T. Zhao, Y. J. Song (NAO, CAS), H. Z. Wu (HUST), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: After the EP-WXT detection of the fast X-ray transient EP250428b (Liu et al., GCN 40277), a follow-up observation was performed by EP-FXT at 2025-04-29T14:04:00 (UTC), about 32 hours after the detection, with an exposure time of 3.0 ks. On-ground analysis of the EP-FXT data identified an uncatalogued X-ray source within the EP-WXT error circle, at the coordinates (J2000): R.A., Dec. = 220.4575, 2.0989 deg, with an uncertainty of 10 arcsec (radius, 90% confidence level, including both statistical and systematic errors). The unabsorbed 0.5-10 keV flux is estimated to be 1.2 (+0.4, -0.4) x 10^-13 erg/cm^2/s, derived using an absorbed power law model with the hydrogen column density fixed to the Galactic value of 3.77 x 10^20 cm^-2 and the photon index fixed at 2.0, due to the limited photon statistics. All uncertainties quoted above are at the 90% confidence level. 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/40285. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38313] EP250428b: GROWTH-India telescope optical upper limit
by GCN Circulars 30 Apr '25

30 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40284 SUBJECT: EP250428b: GROWTH-India telescope optical upper limit DATE: 25/04/30 07:54:42 GMT FROM: anirudhsalgundi(a)gmail.com A. Salgundi (IITB), V. Swain (IITB), D. Eappachen (IIA), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of the EP250428b (Liu et al., GCN #40277) with the 0.7m GROWTH-India Telescope (GIT). Observation started at 2025-04-29T18:21:59 UT, about 1.51 days after the trigger. We obtained single image of 360s in r' filter. The following upper limit was obtained: |MJD (mid)| Filter| Exposure (s)| Limiting Magnitude (AB)| | ----------------- | ----------- |------- | ------------------ | 60794.7652662038| r'| 360| 20.5 The magnitude is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The upper limit is consistent with MASTER (Lipunov et al., GCN #40278), LAST (Konno et al., GCN #40281), SAO RAS (Moskvitin et., GCN #40282), SVOM/VT (Xin et al., GCN #40283). The GROWTH India Telescope (GIT, Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/40284. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38312] EP250428b: SVOM/VT upper limit
by GCN Circulars 30 Apr '25

30 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40283 SUBJECT: EP250428b: SVOM/VT upper limit DATE: 25/04/30 01:39:45 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao(NAOC), M. J. Liu, Q. Y. Wu, T. Zhao, Y. J. Song (NAO, CAS), H. Z. Wu (HUST), C. C. Jin (NAO, CAS), X. H. Han,Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC) report on behalf of the SVOM team and the Einstein Probe (EP) team: SVOM/VT conducted ToO follow-up observations of the EP250428b(Liu et al., GCN 40277). The observation started on 2025-04-29T17:26:22 UT, 2025 Apr 29, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. With the effective exposure time of 2500 seconds, no any new sources were detected in EP/FXT error box (Liu et al., GCN 40277) in stacked images with the 3 sigma upper limit of VT_B=23.2 mag and VT_R=23.0 mag, compared to Legacy survey, at the mid time of 1.487 days after the transient time. This result is consistent with the reports (Konno et al., GCN 40281, Moskvitin et al., GCN 40282). 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/40283. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38311] EP250428b: SAO RAS optical upper limit
by GCN Circulars 29 Apr '25

29 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40282 SUBJECT: EP250428b: SAO RAS optical upper limit DATE: 25/04/29 23:39:13 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova (SAO RAS) report on behalf of the GRB follow-up team. We observed the field of the X-ray transient EP250428b (Liu et al., GCN 40277) with the SAO RAS 1-m telescope Zeiss-1000 on April 29, 20:47:38--21:28:24 UT (t_mid - T0 = 1.6267 days). We obtained 7 x 300 sec. images in Rc band. Within the FXT error circle we detect several sources which are presented in the PanSTARRS images: R.A. Decl. R_mag +/- err #1 14:41:50.4 +02:06:18.0 20.20 +/- 0.10 #2 14:41:50.7 +02:06:13.4 22.86 +/- 0.21 #3 14:41:49.8 +02:05:55.9 22.57 +/- 0.17 Within the FXT error circle we did not detect any new sources down to the limiting magnitude of R_lim = 23.2 (calibrated against R2 magnitudes of nearby UNSO-B1 stars and not corrected for the MW extinction). View this GCN Circular online at https://gcn.nasa.gov/circulars/40282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38310] EP250428b: LAST optical upper limit
by GCN Circulars 29 Apr '25

29 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40281 SUBJECT: EP250428b: LAST optical upper limit DATE: 25/04/29 21:33:20 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), S. Spitzer (WIS), and K. Rybicki (WIS) on behalf of the LAST Collaboration We report observations of the X-ray transient EP250428b (Liu et al., GCN 40277) with the Large Array Survey Telescope (LAST, Ofek et al. 2023; Ben-Ami et al. 2023). We observe the field of EP250428b using four telescopes, each with a FoV of 7.4 deg^2 and no filter (clear - similar to the GAIA Bp band). We began observations at 2025-04-29 18:25:34.194 UTC (T-T0 = 36.3h). We coadd a total of 160x20s exposure images and perform image subtraction using a reference image of the field. We do not detect any new optical source up to a limiting magnitude of 21.66 (AB) within the reported error regions of FXT and WXT. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38309] IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 29 Apr '25

29 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40280 SUBJECT: IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/04/29 19:07:06 GMT FROM: Giacomo Sommani at Ruhr-Universität Bochum <gsommani(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-04-29 at 15:23:15.63 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.496 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140870_26727884.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-04-29 Time: 15:23:15.63 UT RA: 59.68 (+0.47/-0.57 deg 90% PSF containment) J2000 Dec: 25.32 (+0.39/-0.44 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/40280. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38308] GRB 250427A: Swift/UVOT Detection
by GCN Circulars 29 Apr '25

29 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40279 SUBJECT: GRB 250427A: Swift/UVOT Detection DATE: 25/04/29 18:59:07 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift UVOT team: Swift/UVOT observed the field of GRB 250427A detected by Einstein Probe (Wang et al., GCN Circ. 40257) starting 22.9 ks after the burst. A fading optical source was detected in the U-band consistent with the position of the uncatalogued X-ray source detected by Swift/XRT (D'Elia et al., GCN Circ 40268) and the optical afterglow detected by various facilities (Perez-Garcia et al., GCN Circ 40259; Liu et al., GCN Circ. 40260, Becerra et al,. GCN Circ. 40261; Brivio et al., GCN Circ 40264; Pérez-Fournon et al., GCN Circ. 40267; Xi et al., GCN Circ. 40269; Swain et al., GCN Circ 40270; de Wet et al., GCN Circ 40272; Busmann et al., GCN Circ. 40273; Amram et al., GCN Circ 40275). The preliminary detection and 3-sigma upper limits calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 22960 28938 1622 18.74+/-0.07 u 136546 153119 1721 >20.47 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.209 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40279. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38307] EP250428b: Global MASTER-Net observations report
by GCN Circulars 29 Apr '25

29 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40278 SUBJECT: EP250428b: Global MASTER-Net observations report DATE: 25/04/29 18:09:39 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP250428b ( EP Team et al., GCN 40277) errorbox 285 sec after notice time and 1 days 41608 sec after trigger time at 2025-04-29 17:38:59 UT, with upper limit up to 17.6 mag. Observations started at twilight. The observations began at zenith distance = 64 deg. The sun altitude is -15.2 deg. The galactic latitude b = 53 deg., longitude l = 355 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2856874 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 128038 | 2025-04-29 17:38:59 | MASTER-Kislovodsk | (14h 39m 56.30s , +02d 18m 36.2s) | C | 60 | 17.1 | 128993 | 2025-04-29 17:54:54 | MASTER-Kislovodsk | (14h 39m 58.93s , +02d 19m 39.5s) | C | 60 | 17.5 | 129172 | 2025-04-29 17:57:52 | MASTER-Kislovodsk | (14h 39m 52.83s , +02d 19m 59.5s) | C | 60 | 17.6 | 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/40278. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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