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[vsnet-grb-info 37486] Fermi GRB 250225A: Global MASTER-Net observations report
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39474 SUBJECT: Fermi GRB 250225A: Global MASTER-Net observations report DATE: 25/02/25 21:03:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250225A ( Fermi GBM team, GCN 39467) errorbox 44698 sec after notice time and 44737 sec after trigger time at 2025-02-25 18:51:00 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 33 deg. The sun altitude is -19.6 deg. The galactic latitude b = -49 deg., longitude l = 244 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2790801 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 44768 | 2025-02-25 18:51:00 | MASTER-SAAO | (03h 54m 49.41s , -40d 48m 54.8s) | C | 60 | 18.8 | 44847 | 2025-02-25 18:52:19 | MASTER-SAAO | (04h 05m 18.27s , -40d 47m 21.7s) | C | 60 | 18.7 | 44926 | 2025-02-25 18:53:39 | MASTER-SAAO | (03h 48m 24.30s , -38d 53m 35.9s) | C | 60 | 18.5 | 45006 | 2025-02-25 18:54:58 | MASTER-SAAO | (03h 58m 33.77s , -38d 54m 13.2s) | C | 60 | 18.5 | 45085 | 2025-02-25 18:56:18 | MASTER-SAAO | (04h 01m 53.31s , -42d 42m 05.9s) | C | 60 | 18.6 | 45167 | 2025-02-25 18:57:39 | MASTER-SAAO | (04h 12m 37.11s , -42d 43m 05.4s) | C | 60 | 18.9 | 45246 | 2025-02-25 18:58:59 | MASTER-SAAO | (03h 41m 13.44s , -42d 41m 11.6s) | C | 60 | 18.8 | 45325 | 2025-02-25 19:00:18 | MASTER-SAAO | (03h 52m 04.78s , -42d 42m 33.9s) | C | 60 | 19.0 | 45423 | 2025-02-25 19:01:56 | MASTER-SAAO | (03h 54m 49.21s , -40d 47m 23.4s) | C | 60 | 18.7 | 45503 | 2025-02-25 19:03:15 | MASTER-SAAO | (04h 05m 16.54s , -40d 47m 55.2s) | C | 60 | 18.9 | 45741 | 2025-02-25 19:07:13 | MASTER-SAAO | (03h 48m 17.83s , -38d 54m 45.8s) | C | 60 | 18.6 | 45820 | 2025-02-25 19:08:33 | MASTER-SAAO | (03h 58m 39.26s , -38d 54m 26.3s) | C | 60 | 18.5 | 45900 | 2025-02-25 19:09:52 | MASTER-SAAO | (04h 01m 51.26s , -42d 40m 43.1s) | C | 60 | 18.9 | 45979 | 2025-02-25 19:11:12 | MASTER-SAAO | (04h 12m 42.31s , -42d 42m 16.8s) | C | 60 | 18.8 | 46058 | 2025-02-25 19:12:31 | MASTER-SAAO | (03h 41m 16.02s , -42d 40m 55.7s) | C | 60 | 19.1 | 46137 | 2025-02-25 19:13:50 | MASTER-SAAO | (03h 52m 03.12s , -42d 41m 27.8s) | C | 60 | 19.0 | 46217 | 2025-02-25 19:15:09 | MASTER-SAAO | (03h 54m 43.40s , -40d 46m 27.2s) | C | 60 | 18.8 | 46296 | 2025-02-25 19:16:29 | MASTER-SAAO | (04h 05m 22.17s , -40d 47m 26.6s) | C | 60 | 18.7 | 46376 | 2025-02-25 19:17:48 | MASTER-SAAO | (03h 48m 17.65s , -38d 54m 21.8s) | C | 60 | 18.5 | 46456 | 2025-02-25 19:19:08 | MASTER-SAAO | (03h 58m 39.07s , -38d 54m 08.0s) | C | 60 | 18.8 | 46535 | 2025-02-25 19:20:28 | MASTER-SAAO | (04h 01m 51.71s , -42d 40m 26.7s) | C | 60 | 18.6 | 46614 | 2025-02-25 19:21:47 | MASTER-SAAO | (04h 12m 43.06s , -42d 42m 11.9s) | C | 60 | 18.7 | 46695 | 2025-02-25 19:23:08 | MASTER-SAAO | (03h 41m 17.18s , -42d 40m 34.0s) | C | 60 | 18.6 | 46784 | 2025-02-25 19:24:37 | MASTER-SAAO | (03h 52m 01.84s , -42d 41m 05.5s) | C | 60 | 18.9 | 46863 | 2025-02-25 19:25:56 | MASTER-SAAO | (03h 54m 44.70s , -40d 46m 04.3s) | C | 60 | 18.6 | 46943 | 2025-02-25 19:27:15 | MASTER-SAAO | (04h 05m 22.62s , -40d 47m 03.2s) | C | 60 | 18.4 | 47022 | 2025-02-25 19:28:34 | MASTER-SAAO | (03h 48m 17.09s , -38d 53m 59.3s) | C | 60 | 18.5 | 47102 | 2025-02-25 19:29:55 | MASTER-SAAO | (03h 58m 38.43s , -38d 53m 36.6s) | C | 60 | 18.4 | 47182 | 2025-02-25 19:31:14 | MASTER-SAAO | (04h 01m 52.00s , -42d 39m 55.2s) | C | 60 | 18.8 | 47267 | 2025-02-25 19:32:39 | MASTER-SAAO | (04h 12m 43.40s , -42d 41m 44.3s) | C | 60 | 18.4 | 47346 | 2025-02-25 19:33:59 | MASTER-SAAO | (03h 41m 15.66s , -42d 39m 54.0s) | C | 60 | 18.7 | 47426 | 2025-02-25 19:35:18 | MASTER-SAAO | (03h 52m 01.71s , -42d 40m 43.5s) | C | 60 | 18.6 | 47505 | 2025-02-25 19:36:38 | MASTER-SAAO | (03h 54m 44.12s , -40d 45m 42.3s) | C | 60 | 18.5 | 47585 | 2025-02-25 19:37:57 | MASTER-SAAO | (04h 05m 22.69s , -40d 46m 41.4s) | C | 60 | 18.5 | 47664 | 2025-02-25 19:39:17 | MASTER-SAAO | (03h 48m 17.11s , -38d 53m 37.9s) | C | 60 | 18.3 | 47744 | 2025-02-25 19:40:36 | MASTER-SAAO | (03h 58m 38.68s , -38d 53m 36.3s) | C | 60 | 18.3 | 47823 | 2025-02-25 19:41:56 | MASTER-SAAO | (04h 01m 52.08s , -42d 39m 55.6s) | C | 60 | 18.3 | 47907 | 2025-02-25 19:43:20 | MASTER-SAAO | (04h 12m 43.76s , -42d 41m 01.5s) | C | 60 | 18.3 | 47987 | 2025-02-25 19:44:39 | MASTER-SAAO | (03h 41m 15.72s , -42d 39m 30.2s) | C | 60 | 18.6 | 48066 | 2025-02-25 19:45:58 | MASTER-SAAO | (03h 52m 02.90s , -42d 40m 21.6s) | C | 60 | 18.3 | 48145 | 2025-02-25 19:47:18 | MASTER-SAAO | (03h 54m 42.90s , -40d 45m 20.4s) | C | 60 | 17.8 | 48226 | 2025-02-25 19:48:38 | MASTER-SAAO | (04h 05m 21.63s , -40d 46m 19.8s) | C | 60 | 18.5 | 48307 | 2025-02-25 19:49:59 | MASTER-SAAO | (03h 48m 16.28s , -38d 53m 16.1s) | C | 60 | 18.0 | 48386 | 2025-02-25 19:51:18 | MASTER-SAAO | (03h 58m 38.73s , -38d 52m 47.9s) | C | 60 | 17.4 | 48465 | 2025-02-25 19:52:38 | MASTER-SAAO | (04h 01m 52.05s , -42d 39m 32.2s) | C | 60 | 17.3 | 48545 | 2025-02-25 19:53:57 | MASTER-SAAO | (04h 12m 44.00s , -42d 40m 40.8s) | C | 60 | 17.4 | 48624 | 2025-02-25 19:55:16 | MASTER-SAAO | (03h 41m 16.82s , -42d 39m 08.2s) | C | 60 | 16.4 | 48705 | 2025-02-25 19:56:38 | MASTER-SAAO | (03h 52m 01.56s , -42d 40m 01.8s) | C | 60 | 17.2 | 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/39474. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37485] GRB 250225B: Swift detection of a burst
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39473 SUBJECT: GRB 250225B: Swift detection of a burst DATE: 25/02/25 20:00:29 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> M. A. Williams (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:39:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250225B (trigger=1291459). Swift could not slew immediately due to an observing constraint. The BAT on-board calculated location is RA, Dec 306.145, -41.484 which is RA(J2000) = 20h 24m 35s Dec(J2000) = -41d 29' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure (well-separated peaks at T+1, T+60, T+110) with a total duration of about 120 sec. The peak count rate was ~13000 counts/sec (15-350 keV), at ~1 sec after the trigger. Due to a Moon observing constraint, Swift cannot slew to the BAT position until 05:11 UT on 2025 February 26. There will thus be no XRT or UVOT data for this trigger before this time. We note the presence of the Emission-line Galaxy ESO 340-26 in the BAT error box. This is a bright (B=14.8, R=10.9) extended (1.4 arcmin) galaxy at z ~ 0.018 . Burst Advocate for this burst is M. A. Williams (mjw6837 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39473. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37484] EP250223a: GROWTH-India Telescope optical observations
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39472 SUBJECT: EP250223a: GROWTH-India Telescope optical observations DATE: 25/02/25 19:15:48 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> A.P. Saikia, T. Mohan, V. Swain, V. Bhalerao (IITB), D. Eappachen, G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP250223a reported by EP-WXT (Lian et al., GCN 39429) with the 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-02-23T17:05:58 UT, i.e., 2.02 hours after the EP trigger. We obtained a single exposure of 420 seconds each in r' and g' filters. We clearly detected the afterglow in our image at the position given by NOT (Hauptmann et. al., GCN 39436). The photometry result follows as: | MJD (mid) | tmid-t0 (hours) | Filter | Total Exposure (s) | Magnitude (AB) | Limiting Magnitude | | ----------------- | ----------- |------- | ------------------ | -------------- | ------ | | 60729.714907 | 2.08 | r' | 1x420 | 19.18 +/- 0.18 | 19.66 | | 60729.720081 | 2.15 | g' | 1x420 | - | 19.62 | Our result is consistent with Hauptmann et al., (GCN 39436), Wu et al., (GCN 39439), Péréz-Fournon et al., (GCN 39440), Izzo et al., (GCN 39441), Xin et al., (GCN 39445), Guo et al., (GCN 39447). The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. 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/39472. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37483] GRB 250221A: Swift-BAT refined analysis
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39471 SUBJECT: GRB 250221A: Swift-BAT refined analysis DATE: 25/02/25 14:19:03 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Caputo (GSFC) R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-479 to T+600 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250221A (trigger #1290305) (R. Caputo, et al., GCN Circ. 39396). The BAT ground-calculated position is RA, Dec = 59.476, -15.137 deg which is RA(J2000) = 03h 57m 54.4s Dec(J2000) = -15d 08' 11.8" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 19%. The mask-weighted light curve displays a single short pulse. T90 (15-350 keV) is 1.80 +- 0.32 sec (estimated error including systematics). The time-averaged spectrum from T-0.22 to T+1.84 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.43 +- 0.23. The fluence in the 15-150 keV band is 3.9 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.42 sec in the 15-150 keV band is 2.9 +- 0.5 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1290305 View this GCN Circular online at https://gcn.nasa.gov/circulars/39471. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37482] GRB 250223C: SVOM/GRM observation of a long burst
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39470 SUBJECT: GRB 250223C: SVOM/GRM observation of a long burst DATE: 25/02/25 13:44:49 GMT FROM: yqzhang_cl(a)163.com SVOM/GRM team: Yan-Qiu Zhang, Chao Zheng, Chen-Wei Wang, Shi-Jie Zheng, Wen-Jun Tan, Chen-Wei Wang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP) report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by a long burst GRB 250223C at 2025-02-23T16:18:36.500 UTC (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39459). 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 40.50 +/- 15.03 s in the 15-2000 keV band. ECLAIRs was not collecting data at the time of this burst. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250223C.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: Yan-Qiu Zhang (IHEP) (zhangyanqiu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39470. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37481] EP250215A: J band upper limit by SYSU 80cm telescope
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39469 SUBJECT: EP250215A: J band upper limit by SYSU 80cm telescope DATE: 25/02/25 07:01:01 GMT FROM: yanghn8(a)mail2.sysu.edu.cn Hao-Nan Yang, Jia-Qi Lin, Si-Yuan Zhu, Zhong-Nan Dong, Wei-Sen Huang, Pu Lin, Jin-Ji Li, Yan Yu, Hao-Ran Zhang, Chun Chen, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team: We observed the field of EP250215A (Fermi GCN 39327; EP GCN 39329) using the Sun Yat-sen University 80cm infrared telescope with 180 x 20 s exposures in J band. The calculated position is RA. = 156.3301 deg, DEC =-27.6997 deg J2000, from EP/FXT observation. Our observations began at 2025-2-15 17:52:00 UTC, 11.39 hours after the EP trigger. We do not detect any counterpart at the position of the optical afterglow(Liu et al. GCN 39330; Xie et al., GCN 39333; Malesani et al., GCN 39339; and Malesani et al. GCN 39341; R. Sanchez-Ramirez et al. GCN 39343; Jean-Grégoire Ducoin (CPPM) et al. GCN 39344; I. Pérez-Fournon et al. GCN 39348; R.Ruffini et al. GCN 39366; D.Svinkin et al. GCN 39375), down to a 5-sigma depth of J~17.5 Vega magnitudes. View this GCN Circular online at https://gcn.nasa.gov/circulars/39469. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37480] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39468 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates DATE: 25/02/25 06:46:50 GMT FROM: xjh(a)andrew.cmu.edu Lei Hu (CMU), Xander J. Hall (CMU), Tomás Cabrera (CMU), Antonella Palmese (CMU), Igor Andreoni (UNC), Brendan O’Connor (CMU), Keerthi Kunnumkai (CMU), on behalf of the GW-MMADS team The high probability area of the joint LVK/Swift-GUANO alert for the gravitational wave candidate S250223dk (GCN 39443) was observed using the wide-field Dark Energy Camera (DECam) on the 4m Blanco telescope by the Dark Energy Survey Gravitational Wave (DESGW) program (PI: Soares-Santos; GCN 39462). Observations started at 2025-02-24T03:45:38 on the night of the alert, and at 2025-02-25T00:50:13 on the following night. We find that the median 5sigma depths of the exposures are r\~24.7 mag on the first night and r\~24.9 mag on the second night. As part of the Gravitational Wave Multi-Messenger Astronomy DECam Survey (GW-MMADS), we run the SFFT difference imaging (Hu et al. 2022) on the available images using templates from DES, filter out likely stars and moving objects, visually inspect the remaining transients. We posted on TNS new transients from this analysis and report here the most likely extragalactic transients we find within the joint LVK-GUANO skymap 95% credible interval area: | id | AT name | ra | dec | discovery_date (UT) | mag_r | mag_r_err | mag_r-mag_i | | ------------------------ | ---------- | ---------- | ---------- | ----------------------- | ------ | ----- | ----- | | C202502240542297m473928 | AT 2025cqb | 85.623700 | -47.657680 | 2025-02-24T03:58:42 | 23.04 | 0.05 | 0.20 | C202502240549253m474247 | AT 2025cqf | 87.355530 | -47.713117 | 2025-02-24T03:58:42 | 24.44 | 0.20 | N/A | A202502240541155m473906* | AT 2025cpv | 85.314435 | -47.651722 | 2025-02-24T03:45:38 | 23.55 | 0.08 | 0.21 | C202502240541459m473517 | AT 2025cql | 85.441205 | -47.588088 | 2025-02-24T04:24:50 | 24.77 | 0.25 | N/A | C202502240545203m483410 | AT 2025cqm | 86.334777 | -48.569306 | 2025-02-24T03:58:42 | 24.00 | 0.13 | N/A | T202502240543468m475332 | AT 2025cqc | 85.944938 | -47.892308 | 2025-02-24T03:45:38 | 23.00 | 0.05 | 0.21 | C202502240544410m483014 | AT 2025cqe | 86.170896 | -48.503829 | 2025-02-24T03:58:42 | 23.75 | 0.10 | 0.49 | A202502240546005m475901* | AT 2025cqd | 86.502090 | -47.983653 | 2025-02-24T03:45:38 | 22.48 | 0.03 | 0.23 * Possible stellar origin Magnitudes reported are from the discovery date and not corrected from Milky Way extinction. Further analysis is underway. We thank the CTIO and NOIRLab staff for supporting observations and data calibration. View this GCN Circular online at https://gcn.nasa.gov/circulars/39468. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37479] GRB 250225A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39467 SUBJECT: GRB 250225A: Fermi GBM Final Real-time Localization DATE: 25/02/25 06:35:59 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 06:25:23 UT on 25 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250225A (trigger 762157528.045892 / 250225268). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 60.0, Dec = -40.5 (J2000 degrees, equivalent to J2000 04h 00m, -40d 30'), with a statistical uncertainty of 12.1 degrees. The angle from the Fermi LAT boresight is 72.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250225268/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250225268/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250225268/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39467. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37478] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39466 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits DATE: 25/02/25 04:51:53 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> G. Waratkar (IITB), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: We have carried a search [1] for X-ray candidates in Astrosat CZTI data in a 100 sec window around the trigger time of the event S250223dk (UTC 2025-02-23 12:01:15). We use the combined-ext.multiorder.fits map (https://gracedb.ligo.org/api/superevents/S250223dk/files/combined-ext.multi…) for our analysis. CZTI is a coded aperture mask instrument that has considerable effective area for about 29% of the entire sky, but is also sensitive to brighter transients from the entire sky. At the time of the merger, Astrosat's nominal pointing is RA,DEC = 15:49:17.1, 70:18:47.9 (237.32, 70.31), which is ~153 deg away from the maximum probability location. At the time of the merger event, the Earth-satellite-transient angle corresponding to the BAT location is ~126 deg and hence is not occulted by Earth in satellite's frame. In a time interval of 100 sec around the event, the region of the localisation map which is not occulted by Earth in the satellite's frame has a total probability of 1.0 (100%). CZTI data were de-trended to remove orbit-wise background variation. We then searched data from the four independent, identical quadrants to look for coincident spikes in the count rates. Searches were undertaken by binning the data in 0.1s, 1s, and 10s respectively. Statistical fluctuations in background count rates were estimated by using data from 5 preceding orbits. We selected confidence levels such that the probability of a false trigger in a 100 sec window is 10^-4. We do not find any evidence for any hard X-ray transient in this window, in the CZTI energy range of 20-200 keV. We use a detailed mass model of the satellite to calculate the direction-dependent instrument response for points in the visible sky. We then assume the source is modelled as a power law with photon index alpha = -1, and convert our count rate upper limits to direction-dependent flux limits. We obtain the following upper limits for source flux in the 20-200 keV band by taking a probability weighted mean over the visible sky: | Bin (s) | Flux Limit (ergs/cm^2/s) | Fluence Limit (ergs/cm^2) | | ------------ | ------------ | ------------ | | 0.1 | 7.01e-06 | 7.01e-07 | | 1.0 | 1.73e-06 | 1.73e-06 | | 10.0 | 3.01e-07 | 3.01e-06 | 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 EMGW detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=emgw [1] Waratkar et al. ApJ 976, 123 (2024) doi:10.3847/1538-4357/ad84e6 View this GCN Circular online at https://gcn.nasa.gov/circulars/39466. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37477] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39465 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits. DATE: 25/02/25 02:44:55 GMT FROM: Harsh Kumar at Center for Astrophysics | Harvard & Smithsonian <harshkosli13(a)gmail.com> H. Kumar, E. Berger, A. Villar, D. Hiramatsu, P. K. Blanchard, K. D. Soto, S. K. Yadavalli, A. Gagliano, C. Ransome, Anya Nugent, Y. Dong (Harvard) report: We obtained imaging with the IMACS imager on the 6.5m Magellan Baade telescope to search for an optical counterpart following the announcement of Swift/BAT-GUANO 762004910 (GCN #39443) event, coincident with gravitational wave event S250223dk. We obtained 4 x 120-second images in each of g- and r-band, starting about 16.6 hours after the GW trigger, targeting the Swift/BAT-GUANO localization of 5 arcmin around RA(J2000)= 85.341 deg, Dec(J2000)= -47.554, covering ~95% of the joint LVK-Swift/BAT localization 50% credible region. We do not detect new transients above 5-sigma level up to ~23.7 mag in the g-band and ~23.5 mag in the r-band after performing image subtraction with Legacy Survey-DECam images as a reference. We checked for the DECam DESGW candidates (GCN #39462) in our images. One source (AT2025cpq) falls in the area covered by Magellan. The source is marginally detected at <3 Sigma. We performed forced photometry and obtained the following magnitudes: —------------------------------------------ Name | Filter | Magnitude +/- e_magnitude —------------------------------------------ AT2025cpq | g | 24.04 +/- 0.48 AT2025cpq | r | 23.78 +/- 0.28 —------------------------------------------- We thank Yuri Beletsky for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39465. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37476] EP250223a: Kinder optical follow-up observations
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39464 SUBJECT: EP250223a: Kinder optical follow-up observations DATE: 25/02/25 01:49:48 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan (NCU), A. K. H. Kong (NTHU), T.-W. Chen, W.-J. Hou, H.-Y. Hsiao (all NCU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, C.-S. Lin, J.-K. Guo (all NCU), S. Yang, L. L. Fan, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP250223a (Lian et al., GCN 39429) using the 40cm SLT telescope and Lulin One-meter Telescope (LOT) at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first SLT epoch of observations in the i-band started at 12:00:02 UT on the 24th of February 2024 (MJD = 60730.500), 20.92 hrs after the EP trigger. The first LOT epoch of observations in the r-band started at 14:42:53 UT on the 24th of February 2024 (MJD = 60730.613), 23.64 hrs after the EP trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked images, we clearly detected the optical counterpart candidate proposed by Hauptmann et al. (GCN 39436) and confirmed by several other observations (e.g., Levan et al al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Ducoin et al., GCN 39453; and O’Neill et al., GCN39455). We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform PSF photometry on our stacked frames. The details of the observations and measured photometry (in the AB system) are as follows: --------------------------------------------------------------------------------------------------------------------------- Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | i | 60730.500 | 20.92 | 300 * 24 | 19.23 +/- 0.03 | 2".06 | 1.51 LOT | r | 60730.613 | 23.64 | 300 * 6 | 19.79 +/- 0.01 | 1".43 | 2.10 The presented magnitudes were calibrated using the field stars from the Pan-STARRS1 catalog and were not corrected for the expected Galactic foreground extinction corresponding to a reddening of A_i = 0.16 mag and A_r = 0.22 mag, respectively, in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39464. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37475] GRB 250207a: ATCA Radio Upper Limits
by GCN Circulars 25 Feb '25

25 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39463 SUBJECT: GRB 250207a: ATCA Radio Upper Limits DATE: 25/02/25 01:32:43 GMT FROM: agul8829(a)uni.sydney.edu.au A. Gulati (USyd), G. E. Anderson (Curtin), S. Chastain (UNM), A. J. van der Horst (GWU), J. K. Leung (UofT/HUJI), and L. Rhodes (TSI/McGill) on behalf of the ATCA PanRadio GRB collaboration We observed Swift and Fermi-detected GRB 250207A (Ferro et al., GCN 39182; Fermi GBM Collaboration, GCN 39181) as part of The Australia Telescope Compact Array (ATCA) "PanRadio GRB" Large Project C3542 (PI: G. Anderson) at 5.5 and 9 GHz on 2025-02-12, 2025-02-14 and 2025-02-21. No radio sources were detected near the Swift/XRT enhanced position (Osborne et al., GCN 39217 )in any of the observation epochs. The 3-sigma upper limits for the 9 GHz observations are 174, 96, and 60 uJy respectively. We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO. View this GCN Circular online at https://gcn.nasa.gov/circulars/39463. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37474] LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39462 SUBJECT: LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates DATE: 25/02/24 22:36:16 GMT FROM: Isaac McMahon at University of Zürich <isaac.mcmahon(a)ligo.org> I. McMahon (UZH), S. MacBride (UZH), H. T. Diehl (FNAL), S. Kaur (UZH), L. Joseph (Benedictine U.), N. Sherman (Boston U.), K. Herner (Fermilab), M. Soares-Santos (UZH), reporting on behalf of the Dark Energy Survey Gravitational Wave (DESGW) Team: At 03:45:38 UTC, the Dark Energy Camera (DECam) began observing in response to the joint LVK/Swift-BAT RAVEN alert issued for the candidate gravitational-wave event S250223dk (GCN 39443). We observed two fields centered on the following ICRS coordinates (85.80,-47.60) (85.83,-47.63) Both fields were observed in DECam g, r, i, and z filters with 360 second exposures. The limiting magnitude achieved is 23.36 in r-band. Images were processed by our difference imaging pipeline (Herner et al. 2020) using DES and public DECam images as templates. We employ the autoscan machine learning code (Goldstein et al. 2015) to reject subtraction artifacts. Candidates were initially selected by requiring at least two high signal to noise detections, which were separated in time in order to reject moving objects. We also require an autoscan score of at least 0.7 on at least one of those detections. After candidate selection, we report five high confidence candidates (listed below). After vetting and identification, four candidates were classified as nuclear candidates (likely AGNs), one candidate (2017239) has been labeled as a possible supernova. All candidates have a host galaxy match within 1 arcsecond. None of the candidate hosts are included in the ALLWISE and MILLIQUAS AGN catalogs (Secrest et. al 2015, Flesch 2023). No other candidates were found in the area. We encourage followup of the five candidates identified herein. | id | AT name | ra | dec | discovery_date (UT) | mag_g | mag_g_err | mag_r | mag_r_err | mag_i | mag_i_err | mag_z | mag_z_err | | --------------- | ---------- | ---------- | ---------- | ----------------------- | ------ | ----- | ------ | ----- | ------ | ----- | ------ | ----- | | 2014974 | AT2025cpl | 86.327994 | -47.827215 | 2025-02-24 03:45:38.271 | 22.487 | 0.043 | 22.151 | 0.031 | 21.744 | 0.053 | 21.894 | 0.106 | | 2014991 | AT2025cpm | 86.516403 | -47.893872 | 2025-02-24 03:45:38.271 | 23.448 | 0.107 | 22.905 | 0.060 | 22.453 | 0.103 | 22.308 | 0.153 | | 2015571 | AT2025cpo | 86.105565 | -47.689987 | 2025-02-24 03:45:38.271 | 22.972 | 0.053 | N/A | N/A | 22.423 | 0.084 | 22.765 | 0.203 | | 2015600 | AT2025cpp | 86.176728 | -47.763957 | 2025-02-24 03:52:10.108 | 21.980 | 0.024 | N/A | N/A | 22.097 | 0.061 | 22.312 | 0.132 | | 2017239 | AT2025cpq | 85.552523 | -47.577823 | 2025-02-24 03:58:42.138 | 24.503 | 0.268 | 23.980 | 0.161 | 23.972 | 0.320 | 24.265 | 0.851 | The DECam Search & Discovery Program for Optical Signatures of Gravitational Wave Events (DESGW) is carried out by the Dark Energy Survey (DES) collaboration in partnership with wide ranging groups in the community. DESGW uses data obtained with the Dark Energy Camera (DECam), which was constructed by the DES collaboration with support from the Department of Energy and member institutions, and utilizes data as distributed by the Science Data Archive at NOIRLAB. NOIRLAB is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank the Cerro Tololo observatory staff for their support in acquiring these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39462. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37473] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39461 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations DATE: 25/02/24 19:45:19 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi-GBM Team: For S250223dk and the Swift/BAT-GUANO ID 762004910 (The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration along with the Swift/BAT-GUANO team, GCN 39443) and using the combined skymap combined-ext.multiorder.fits,3, Fermi-GBM was observing 100% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S250223dk, neither for the Swift/BAT-GUANO trigger ID 762004910. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. Part of the joint localization region is behind the Earth for Fermi, located at RA=267.1, Dec=-5.5 with a radius of 68.0 degrees. We therefore set upper limits on impulsive gamma-ray emission for the joint localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by the joint LVK-Swift/BAT localization probability (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 2.00 2.90 6.40 1.024 s: 0.69 0.95 1.90 8.192 s: 0.23 0.32 0.63 Assuming the median luminosity distance of 6033 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128s: 14.15 16.94 64.06 1.024s: 4.88 5.55 19.02 8.192s: 1.63 1.87 6.31 View this GCN Circular online at https://gcn.nasa.gov/circulars/39461. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37472] GRB 250119B: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39460 SUBJECT: GRB 250119B: VZLUSAT-2 detection DATE: 25/02/24 18:21:07 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250119B (FERMI/GBM detection: GCN 38979; INTEGRAL/SPI-ACS detection: GCN Circular 38997; Swift/BAT-GUANO detection: GCN 39007; Konus/Wind detection: GCN 39016; NuSTAR detection at 2025-01-19 08:27:23 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2025-01-19 08:27:44 UTC. The T90 duration is 41 s and the significance during T90 reaches 66 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250119B_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39460. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37471] GRB 250223C: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39459 SUBJECT: GRB 250223C: Fermi GBM Final Real-time Localization DATE: 25/02/24 17:27:23 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 16:18:20 UT on 23 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250223C (trigger 762020305.175056 / 250223679). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 262.6, Dec = 41.0 (J2000 degrees, equivalent to J2000 17h 30m, 41d 00'), with a statistical uncertainty of 5.1 degrees. The angle from the Fermi LAT boresight is 41.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223679/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39459. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37470] GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39458 SUBJECT: GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert DATE: 25/02/24 16:54:52 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, B. P. Gompertz, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the joint LVK/Swift-BAT RAVEN alert (LIGO, Virgo, KAGRA and Swift/BAT-GUANO teams, GCN 39443). Targeted observations of the combined 90% credible region (using the combined-ext.multiorder.fits,2 skymap) were performed by GOTO-South between 2025-02-24 09:41:31 UT (+21.67h) and 2025-02-24 13:18:31 (+25.28h) UT. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. In the 5 arcmin circle centred at RA = 85.341, Dec = -47.544, containing 52% of the integrated joint probability (LIGO, Virgo, KAGRA and Swift/BAT-GUANO teams, GCN 39443), no credible counterpart candidates are identified to a 3-sigma limiting magnitude of L > 21.1 mag. Furthermore, no candidate optical counterparts are identified within the <1 deg2 combined 90% LVK+Swift/BAT-GUANO credible region. In addition to the targeted response, serendipitous imaging from the all-sky survey was obtained for the 90% credible region defined by the NITRATES search, starting from 2025-02-23 12:03:34 UT (+0.04h). This resulted in a total coverage of 1621 deg^2 within the 90% localisation contour of Swift/BAT-GUANO, corresponding to ~41.6% of its total 2D localisation probability. No credible optical counterparts were identified within this region. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39458. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37469] GRB 250202B: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39457 SUBJECT: GRB 250202B: VZLUSAT-2 detection DATE: 25/02/24 15:10:59 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250202B (FERMI/GBM: GCN Circular 39120; AstroSat/CZTI: GCN Circular 39122; NuSTAR detection: GCN 39135; Konus/Wind detection: GCN 39149; CALET/CGBM detection: trigger no. 1422503847; INTEGRAL/SPI-ACS peak detection at 2025-02-02 ~03:57:20 UTC) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2025-02-02 03:57:18 UTC. The T90 duration is 87 s and the significance during T90 reaches 80 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250202B_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39457. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37468] GRB 250219A: EP-FXT afterglow detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39456 SUBJECT: GRB 250219A: EP-FXT afterglow detection DATE: 25/02/24 14:43:44 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA), P. Y. Han, C. X. Zhang (HUST), J. Yang (NJU), X. Tian (GXU), D. F. Hu (PMO, CAS), W. Chen (NAO, CAS), J. Guan, C. K. Li, Y . Chen, S. M. Jia, W. W. Cui, D. W. Han, W. Li, C. Z. Liu, F . J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F . Zhao (IHEP , CAS), Y . Liu, C. C. Jin, C. Zhang, Z. X. Ling (NAOC,CAS), B. Cordier (CEA) on behalf of the SVOM and Einstein Probe teams We performed a follow-up observation of GRB 250219A (Daigne et al., GCN 39376) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-02-21T07:04:16 (T-TGRB ~ 1.63 days) for about 3ks of exposure in total. An uncatalogued X-ray source is detected by both FXT-A and FXT-B at the position of the x-ray afterglow candidate reported by Swift/XRT (Kennea et al., GCN 39379). This position is also consistent with the optical afterglow detected by SVOM/VT (Xin et al., GCN 39380), COLIBRÍ (Magnani et al. GCN 39382) and the NOT (Fu et al., GCN 39383). A preliminary analysis shows that the spectrum can be fitted with an absorbed power law with nH=1.53*10^20 cm^-2 and a photon index of 1.53 (-0.68/+0.70) . The observed flux in the 0.3-10.0 keV is 4.4 (+2.2/-1.1)*10^-13 erg/s/cm^2. Compared to the Swift/XRT epoch Kennea et al., GCN 39379), the observed source flux has faded by almost one order of magnitude with a temporal slope alpha~-0.56. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/39456. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37467] EP250223a: GOTO optical afterglow detections
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39455 SUBJECT: EP250223a: GOTO optical afterglow detections DATE: 25/02/24 13:59:07 GMT FROM: d.s.oneill(a)bham.ac.uk D. O’Neill, B. P. Gompertz, A. J. Levan, K. Ulaczyk, G. Ramsay, A. Kumar, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the EP/WXT alert WXT01709131863 (Lian et al. GCN 39429). Three epochs of targeted observations were performed: at 2025-02-24 09:56:36 UT (+18.9h post trigger), 2025-02-24 11:04:37 UT (+20.0h post trigger), and 2025-02-24 12:12:37 UT (+21.1h post trigger). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. We detect the optical afterglow (Hauptmann et al., GCN 39436; Levan et al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Brivio et al., GCN 39450; Ducoin et al., GCN 39453) with magnitudes of L (400-700 nm) = 20.04 ± 0.15 mag (+18.9h), L = 19.78 ± 0.11 mag (+20.0h) and L = 19.97 ± 0.14 mag (+21.1h). Our measurements indicate no fading of the afterglow between 18 and 21 hours after trigger, continuing the shallow evolution noted by Ducoin et al. during the first 6 - 15 hours (GCN 39453). GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39455. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37466] GRB 250222A: SVOM/GRM observation of a burst
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39454 SUBJECT: GRB 250222A: SVOM/GRM observation of a burst DATE: 25/02/24 13:15:04 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: Frédéric Piron (LUPM), Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia, Sébastien Guillot (IRAP) report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a long burst GRB 250222A (SVOM trigger reference: sb25022201) at 2025-02-22T14:24:26.100 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve of 15 to 600 keV shows that this burst consists of multi-pulses with a T90 of 4.3 +0.6/-0.5 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250222A.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 284.2 deg DEC: -61.0 deg Error: 1.6 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, this burst was detected by the Count-Rate Trigger onboard ECLAIRs, as an increase in counts over background, but it was not localized by the coded-mask imaging process, which confirms that the burst occurred outside the ECLAIRs field of view. 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/39454. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37465] EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39453 SUBJECT: EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading DATE: 25/02/24 13:00:21 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Jean-Grégoire Ducoin (CPPM), Francesco Magnani (CPPM), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Kin Ocelotl López (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of EP250223a (Lian et al., GCN Circ. 39429), detected also by Swift/XRT (Kennea et al., GCN Circ. 39437), with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-24 04:59 to 07:19 UTC (13.9 to 16.3 hours after the trigger) and obtained 96 minutes of exposure in the r filter. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction. In a stacked image of our first 50 minutes of exposure, we detect a source at the position of the optical afterglow candidate reported by Hauptmann et al. (GCN Circ. 39436) and many other groups (GCN Circs. 39439, 39440, 39441, 39445, 39447, and 39449) with magnitude: r = 19.87 +/- 0.01 Comparing our r magnitude to the similar ones reported by Hauptmann et al. (GCN Circ. 39436) and Pérez-Fournon et al. (GCN Circ. 39440), we see no more than slow fading between about 6 and 15 hours. We encourage continued monitoring of this source. 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/39453. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37464] GRB 250210A: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39452 SUBJECT: GRB 250210A: VZLUSAT-2 detection DATE: 25/02/24 12:50:48 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250210A (FERMI/GBM: GCN Circular 39262; AstroSat/CZTI: GCN Circular 39267; INTEGRAL/SPI-ACS: CGN Circular 39268; SVOM/GRM: CGN Circular 39282; GRBAlpha detection: GCN 39313) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector unit no. 0. The detection was confirmed at the peak time 2025-02-10 05:31:59 UTC. The T90 duration is 49 s and the significance during T90 reaches 10 sigma. The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250210A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39452. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37463] GRB 250206A: VZLUSAT-2 detection
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39451 SUBJECT: GRB 250206A: VZLUSAT-2 detection DATE: 25/02/24 12:41:13 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250206A (Fermi/GBM detection: GCN 39172; Fermi/LAT detection: GCN 39233; EIRSAT-1/GMOD detection: GCN 39236; Konus/Wind detection: GCN 39283; INTEGRAL/SPI-ACS peak detection at 2025-02-06 ~19:51:45 UTC) was detected by the GRB detectors on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector units no. 0 and no. 1. The detection was confirmed at the peak time 2025-02-06 19:51:43 (19:51:46) UTC. The T90 duration is 67 s (63 s) and the significance during T90 reaches 11 sigma (17 sigma) for detector unit no. 0 (no. 1). The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250206A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/39451. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37462] EP250223a: REM NIR upper limit
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39450 SUBJECT: EP250223a: REM NIR upper limit DATE: 25/02/24 11:40:05 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 EP250223a (Lian et al., GCN 39429; Wang et al., GCN 39448), also detected by Swift/XRT (Kennea et al., GCN 39437) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the J, H, and K bands, started on 2025 February 24 at 01:29:31 UT (i.e. 10.4 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not find any counterpart at the position of the reported optical afterglow (Hauptmann et al., GCN 39436; Levan et al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo & Malesani, GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449) down to the following 3sigma limit: H > 17.6 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 10.85 hours after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39450. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37461] EP250223a: TRT optical afterglow observation
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39449 SUBJECT: EP250223a: TRT optical afterglow observation DATE: 25/02/24 11:34:23 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> J. An, S.Q. Jiang, N.C. Sun (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), Z. Fan, W.X. Li, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of EP250223a detected by EP (Lian et al., GCN 39429; Wang et al., GCN 39448), and observed by Swift/XRT (Kennea et al., GCN 39437), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 00:37:15.66 UTC on 2025-02-24, i.e., 9.544 hrs after the EP trigger, and a series of 200 s frames were obtained in B, V, R and I bands. The optical afterglow (Wu et al., GCN 39439; Guo et al., GCN 39447; Izzo et al., GCN 39441; Xin et al., GCN 39445; Pérez-Fournon et al., GCN 39440; Hauptmann et al., GCN 39436; Levan et al., GCN 39438) is clearly detected in our stacked images with: | T (mid) - T0 (hours)| band | mag | error | | 9.816 | B | 21.32 | 0.14 | | 9.996 | V | 20.17 | 0.07 | | 10.176 | R | 19.86 | 0.07 | | 10.356 | I | 19.41 | 0.12 | calibrated with Panstarrs-DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39449. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37460] EP250223a: refined analysis of the EP-WXT and FXT observations
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39448 SUBJECT: EP250223a: refined analysis of the EP-WXT and FXT observations DATE: 25/02/24 10:08:07 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO, CAS), T. Y. Lian, W. J. Zhang (NAOC, CAS), X. Tian (GXU), R. Z. Li(YNAO, CAS), H. W. Pan (NAOC, CAS) report on behalf of the Einstein Probe team: The X-ray transient EP250223a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Lian et al., GCN 39429), and followed by the Swift XRT (Kennea et al., GCN 39437) and several optical telescopes (Levan et al., GCN 39436, Wu et al., GCN 39439, Pérez-Fournon et al., GCN 39440, Izzo et al., GCN 39441, Xin et al., GCN 39445) at the redshift of 2.756 (Levan et al., GCN 39438). The refined analysis of the WXT data shows that the event started at 2025-02-23T15:02:05.66 (UTC) and lasted for 140 s with the peak flux of 2 x 10^(-9) erg/s/cm^2, before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 1.36 x 10^21 cm^-2 and a photon index of 2.1 (-/+0.6). The derived average unabsorbed 0.5-4 keV flux is 4.4 (-1.1/+1.4) x 10^(-10) erg/s/cm^2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed about two minutes later. The on-ground analysis shows that an uncatalogued source was detected at R.A. = 98.2748, DEC = -22.4443 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic equivalent hydrogen column density of 1.36 x 10^21 cm^-2 and a photon index of 1.97 (-/+0.05). The derived average unabsorbed 0.5-10 keV flux is 2.5 (-/+0.1) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Further follow-up observations with EP-FXT have been scheduled. 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/39448. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37459] EP250223a: 1.6m Mephisto and 50cm array observations
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39447 SUBJECT: EP250223a: 1.6m Mephisto and 50cm array observations DATE: 25/02/24 10:02:52 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Helong Guo, Guowang Du, Yu Pan, Xinlei Chen, Brajesh Kumar, Xiaotong Chen, Yiheng Xie, Yuan Fang, Xingzhu Zou, Yuanpei Yang, Jinghua Zhang, Dezi Liu, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP250223a detected by EP Team (Lian et al., GCN 39429) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) and 50cm array facilities of Yunnan University located at Lijiang Observatory. Simultaneous uvgr band images with different exposure times were acquired with Mephisto starting from 15:20:12 2025-02-23 UT (~15.6 minutes after the trigger) and with 50cm array in iz bands starting from 15:49:08 2025-02-23 UT (~44.5 minutes after the trigger). The afterglow candidate (Lipunov et al., GCN 39434; Hauptmann et al., GCN 39436; Kennea et al., GCN 39437; Levan et al., GCN 39438; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445) is clearly detected in each v, g, r band and in the stacked u band images taken with Mephisto. The candidate is also visible in the stacked i band image of 50 cm array but not in the stacked z band. The preliminary magnitudes and 3-sigma upper limit are below: 1.6m Mephisto Start_Time(UT) | Band | Exp(s) | Mag/LimMag(AB) --------------------|------|--------|---------------- 2025-02-23T16:00:53 | u | 300*3 | 20.97 +/- 0.29 2025-02-23T15:25:14 | v | 180 | 19.93 +/- 0.22 2025-02-23T15:20:12 | g | 10 | 18.11 +/- 0.12 2025-02-23T15:25:14 | r | 50 | 18.17 +/- 0.07 50CM array Start_Time(UT) | Band | Exp(s) | Mag/LimMag(AB) --------------------|------|--------|--------------- 2025-02-23T15:49:08 | i | 300*3 | 18.89 +/- 0.11 2025-02-23T15:49:08 | z | 300*3 | >18.81 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. The 50cm array consists of two 50cm telescopes for wide-field surveys and also serves as the supporting facility for monitoring the Mephisto detected targets. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39447. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37458] GRB 250221A: TNOT detection of the optical counterpart
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39446 SUBJECT: GRB 250221A: TNOT detection of the optical counterpart DATE: 25/02/24 09:24:45 GMT FROM: Xiaofeng Wang at Tsinghua University <wang_xf(a)mail.tsinghua.edu.cn> A. Iskandar（XAO), H.-C. Zhu (THU)，X.-F. Wang, and L.-T. Wang (XAO) report the optical detection of the afterglow of GRB 250221A (Francile et al., GCN 39395; Caputo et al., GCN 39396; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCNs 39422,39424,39426,39427; Ghosh et al., GCN 39425). We obtained the r-band images (~2.40 days after the burst) with the 80~cm Tsinghua-Nanshan Optical Telescope (TNOT) located at Nanshan Station of Xinjiang Astronomy Observatory, starting on 2025-02-23 (UT) 13:05:49. The afterglow is clearly detected on the stacked images, with the following magnitude: r = 20.46 +- 0.17 mag (MJD =60698.5457) The above photometric result is calibrated against the Pan-STARRS catalog without a correction for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39446. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37457] EP250223a: SVOM/VT optical observation
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39445 SUBJECT: EP250223a: SVOM/VT optical observation DATE: 25/02/24 07:51:36 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> L.P. Xin, Y.L. Qiu(NAOC), Y. Wang(PMO),H.L. Li, C. Wu, Z.H. Yao, Y. N. Ma, X.H. Han, H.B. Cai, J. Wang, Y. Xu, J.Y. Wei(NAOC), J. T. Palmerio(CEA/Irfu) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observations of the EP250223a (Lian et al., GCN 39429) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. The afterglow(Benjamin et al., GCN 39436) was clearly detected within the errorbox of EP/FXT (Lian et al., GCN 39429) in VT_R and VT_B images. The afterglow was fading during our observations and the brightness was estimated to be 19.21+/-0.05 mag in AB magnitude in VT_R, and 20.11+/-0.05 mag in AB magnitude in VT_B, at the mid time of 3.7 hours post the 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/39445. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37456] LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39444 SUBJECT: LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart DATE: 25/02/24 04:53:21 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), William H. Lee (UNAM), Océlotl López (UNAM), Camila Angulo Valdez (UNAM), Rosa L. Becerra (U Roma), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), and Margarita Pereyra (UNAM), and Eleonora Troja (U Roma) report: We imaged the field of the Swift/BAT-GUANO trigger possibly associated with LIGO/Virgo/KAGRA S250223dk (GCN Circ. 39443) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico (http://ddoti.astroscu.unam.mx). We observed the whole BAT error region from 2025-02-24 03:56 UTC to 04:24 UTC (15.9 to 16.4 hours after the GW event) at extremely high airmass. We obtained a total exposure of 24 minutes. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no uncatalogued sources within the observed BAT error region to a 5-sigma AB limiting magnitude of w > 20.0. Our photometry is in the AB system and is not corrected for Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39444. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37455] LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39443 SUBJECT: LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger DATE: 25/02/24 03:12:15 GMT FROM: minghuidu1993(a)gmail.com The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration along with the Swift/BAT-GUANO team report: We identified the compact binary merger candidate S250223dk during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at T0 = 2025-02-23 12:01:15.360 UTC (GPS time: 1424347293.360). The candidate was found by the GstLAL [1] analysis pipeline. S250223dk is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.4e-05 Hz, or about one in 19 hours. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250223dk The classification of the GW signal, in order of descending probability, is Terrestrial (92%), BBH (8%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Five GW-only sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [3], distributed via GCN notice about a minute after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 5 minutes after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 12 hours after the candidate event time. * bayestar.multiorder.fits,3, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 12 hours after the candidate event time. * bayestar.multiorder.fits,4, an initial localization generated by BAYESTAR [3], distributed via GCN notice about 13 hours after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,4. For the bayestar.multiorder.fits,4 sky map, the 90% credible region is 3203 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 6033 +/- 1778 Mpc (a posteriori mean +/- standard deviation). The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; [4]). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-45,+45] seconds around the time of the GW alert. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES [5], performed on the temporal window [T0-20 s, T0+20 s], detects a burst candidate with a sqrt(TS) of 8.0 in a 8.192 s analysis time bin, starting at T0 - 10.240 s The 90% credible area is 2666 deg2 and the 50% credible area is <1 deg2. The integrated probability inside the coded field of view is 83%. The joint LVK-Swift/BAT localization probability map peaks at RA = 85.341 deg, Dec = -47.554 deg. A circle with a radius of 5 arcmin around this position contains 52% of the integrated joint probability. Swift has already initiated TOO followup of this position with XRT and UVOT. Results will be reported in future circulars. We encourage followup by other, more sensitive, facilities. A plot of the Swift/BAT probability skymap can be viewed here: https://guano.swift.psu.edu/trigger_report?id=762004910/#:~:text=Probabilit… The Swift/BAT probability skymap file can be downloaded from the link here: https://guano.swift.psu.edu/files/762004910/0_n_PROBMAP Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=762004910 A search performed by the RAVEN pipeline [6] found a temporal coincidence between S250223dk and a sub-threshold Swift/BAT trigger with ID 762004910. The GRB trigger time is 10.24 seconds before the GW candidate event. The estimated joint false alarm rate for the coincidence using just timing info is 1.9e-07 Hz, or about one in a month. The GRB candidate was found during a joint targeted search between the LIGO/Virgo/KAGRA collaboration and Swift/BAT-GUANO, and has a false alarm rate of 7.4e-05 Hz, or about one in 3 hours.Combined sky maps are also available: * combined-ext.multiorder.fits,0, an initial localization, distributed via GCN notice about 12 hours after the candidate event time. * combined-ext.multiorder.fits,1, an initial localization, distributed via GCN notice about 12 hours after the candidate event time. * combined-ext.multiorder.fits,2, an initial localization, distributed via GCN notice about 13 hours after the candidate event time. For the combined-ext.multiorder.fits,2 sky map, the 90% credible region is <1 deg2. The joint localization is dominated by the Swift/BAT-GUANO candidate. Considering the overlap of the individual sky maps, the estimated joint false alarm rate for the spatial and temporal coincidence is 5.1e-09 Hz, or about one in 6 years. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [3] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 [4] Tohuvavohu et al. ApJ, 900, 1 (2020) [5] DeLaunay & Tohuvavohu, ApJ, 941, 169 (2022) [6] Urban, A. L. 2016, Ph.D. Thesis https://dc.uwm.edu/etd/1218 and Piotrzkowski, B. J. 2022, Ph.D. Thesis https://dc.uwm.edu/etd/3060 View this GCN Circular online at https://gcn.nasa.gov/circulars/39443. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37454] The EP-WXT trigger 01709131882 is likely a flaring star
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39442 SUBJECT: The EP-WXT trigger 01709131882 is likely a flaring star DATE: 25/02/24 02:20:45 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO, CAS), H. Z. Wu (HUST), H. He, S.-E. Xu (WHU), W. Yuan (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131882) on 2025-02-23 21:47:14 (UTC) is likely a stellar flare associated with a BY Dra Variable V1217 Cen. The estimated flux of the flare is around 1.0 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 5.1 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard 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/39442. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37453] EP250223a: OASDG optical observations
by GCN Circulars 24 Feb '25

24 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39441 SUBJECT: EP250223a: OASDG optical observations DATE: 25/02/24 00:06:24 GMT FROM: luca.izzo(a)inaf.it L. Izzo (INAF-OACn and DARK/NBI), and D. B. Malesani (DAWN/NBI and Radboud Univ.) report: We observed the field of EP250223a (Lian et al., GCN #39429) using the 0.5-m T1 telescope of the Osservatorio Astronomico S. Di Giacomo, located in Agerola, Italy. Our observations started on 2025 February 23 at 18:15 UT, approximately 3.19 hours after the GRB trigger. We acquired a series of 6x300 s images in the Rc filter. In the stacked image, we detect a faint source consistent with the X-ray afterglow reported by EP/FXT (Lian et al., GCN #39429), and by Swift-XRT (Kennea et al., GCN #39437), and with the optical counterpart reported by several other telescopes (Hauptmann et al., GCN #39436; Levan et al., GCN #39438; Wu et al., GCN #39439; Perez-Fournon et al., GCN #39440). We measure a preliminary magnitude of Rc = 19.6 +/- 0.2 mag (AB), calibrated against nearby stars from the Pan-STARRS catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/39441. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37452] EP250223a: LCO detection of the afterglow
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39440 SUBJECT: EP250223a: LCO detection of the afterglow DATE: 25/02/23 23:49:41 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin, D. Aguado, J.A. Acosta-Pulido, A. López-Oramas, D. Nespral (IAC and ULL), F. Acero (CEA Saclay and IAC), N.C. Sun (UCAS), W. Li, Y. Wang, Z. Niu (NAOC), D. Cano-Morales, I. Correa-Plasencia, and A.E. Hernández-Díaz (ULL) We observed the location of EP250223a (Lian et al., GCN circ. 39429), detected also by Swift XRT (Kennea et al., GCN circ. 39437), with two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Sutherland Observatory (South Africa). We obtained first a 600-sec exposure in the SDSS r' filter, that started at 2025-02-23 19:47:12 UT, e.g. 4.71 hr after the EP trigger, followed by 300-sec exposures in the SDSS i' and g' filters. The optical afterglow candidate reported by Hauptmann et al. (GCN circ. 39436) is clearly detected in the three images. We measured the following magnitudes, calibrated against PanSTARRS DR2 stars and not corrected for Galactic extinction: Date | UT start | T (mid) - T0 (hours) | mag | error | filter | ---------------------------------------------------------------------- 2025-02-23 19:47:12 4.79 19.73 0.03 r' 2025-02-23 21:38:41 6.61 19.74 0.06 i' 2025-02-23 21:42:28 6.67 20.77 0.10 g' A redshift of z = 2.756 has been reported by Levan et al. (GCN circ. 39438). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/39440. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37451] EP250223a: early optical detection by BOOTES-4
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39439 SUBJECT: EP250223a: early optical detection by BOOTES-4 DATE: 25/02/23 23:38:26 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S.-Y. Wu, I. Perez-Garcia, E. Fernandez-Garcia, M. D. Caballero-Garcia, G. Garcia-Segura, S. Guziy, R. Sanchez-Ramirez and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. de Malaga), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), and D. R. Xiong, J. M. Bai, Y. F. Fan, C. J. Wang, Y. X. Xin, X. H. Zhao, J. R. Mao, B. K. Lun, K. Ye (Yunnan Observatories/CAS, Kunming) on behalf of a larger collaboration, report: Following the detection of EP250223a by EP/WXT (Lian et al. GCNC 39429), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically responded to this burst starting on Feb. 23, 15:16:38 UT (~12 min after trigger). At the position of the EP/FXT X-ray source (also recorded by Swift/XRT, Kennea et al. GCNC 39437), an optical counterpart is detected, for which we measure a magnitude of 18.4 +/- 0.1 (60s, clear filter, comparable with Gmag of Gaia DR3), which also consistent with the object reported by NOT at a later stage (Hauptmann et al. GCNC 39426, Levan et al. GCNC 39438). Further analysis of the additional images is ongoing. We thank the staff at Lijiang observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/39439. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37450] EP250223a: NOT redshift z = 2.756
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39438 SUBJECT: EP250223a: NOT redshift z = 2.756 DATE: 25/02/23 23:17:57 GMT FROM: Andrew Levan at Radboud University <a.levan(a)astro.ru.nl> Andrew J. Levan (Radboud and Warwick), Luca Izzo (INAF, Naples and DARK/NBI), Daniele B. Malesani (DAWN/NBI and Radboud), Antonio Martin-Carrillo (UCD), Franz E. Bauer (PUC), Peter G. Jonker (Radboud), Benjamin N. Hauptmann (NOT and DTU Space), Yfke Bethlehem (Kapteyn Astronomical Institute, Groningen, and ING), and Dong Xu (NAOC), report on behalf of a larger collaboration: Further to the identification of the likely optical counterpart (Hauptmann et al., GCN 39436) of EP 250223a (Lian et al., GCN 39429), we obtained spectroscopic observations with the Nordic Optical Telescope, beginning at 21:18 UT. A total of 4x900 s observations were obtained using grism #4. The observations reveal a strong continuum with a pronounced suppression at ~4550 AA, which we interpret as arising from damped Lyman-alpha absorption. In addition we detect a number of narrow metal lines, among which Fe II, Al II, C II, O I, Si II, which allow us to fix the redshift to z = 2.756. The spectral shape and redshift, as well as the detection of an X-ray counterpart at a consistent position with Swift (Kennea et al., GCN 39437), secure the source as the counterpart of EP250223a. View this GCN Circular online at https://gcn.nasa.gov/circulars/39438. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37449] EP250223a: Swift/XRT localization
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39437 SUBJECT: EP250223a: Swift/XRT localization DATE: 25/02/23 21:48:18 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea, C. Gronwall (PSU) and P. A. Evans (Leicester) report on behalf of the Swift Team: At 16:36:15UT Swift began a target-of-opportunity observation of the transient EP250223a (GCN #39429), approximately 1.6 hours after the Einstein Probe trigger. We detect an an uncatalogued point source above the RASS limit at the following location: RA/Dec(J2000) = 98.27464, -22.4449, which is equivalent to: RA(J2000) = 06h 33m 05.91s, Dec(J2000) = -22° 26′ 41.8″, with an estimated uncertainty radius of 3.8 arc-seconds (90% confidence). This position lies 8.5 arc-seconds from the EP WXT position reported in GCN #39429. The peak flux during the XRT observation was 5.4 (±1.0) × 10^-12 erg cm^-2 s^-1 (0.3 - 10 keV). View this GCN Circular online at https://gcn.nasa.gov/circulars/39437. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37448] EP250223a: NOT optical afterglow candidate
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39436 SUBJECT: EP250223a: NOT optical afterglow candidate DATE: 25/02/23 21:46:49 GMT FROM: Andrew Levan at Radboud University <a.levan(a)astro.ru.nl> Benjamin N. Hauptmann (NOT and DTU Space), Yfke Bethlehem (Kapteyn Astronomical Institute, Groningen, and ING), Andrew J. Levan (Radboud and Warwick), Daniele B. Malesani (DAWN/NBI and Radboud), Antonio Martin-Carrillo (UCD), Franz E. Bauer (PUC), Peter G. Jonker (Radboud) and Dong Xu (NAOC), report on behalf of a larger collaboration: We observed the location of EP250223a (Lian et al. GCN 39429) with the Nordic Optical Telescope (NOT). Observations in the r-band began at 20:36 UT, approximately 5.53 hr after the trigger time. In the first 300 s exposure we clearly detect a new point source, not visible in archival DSS and Pan-STARRS imaging of this field, at a location of RA(J2000) = 06:33:05.723 DEC(J2000) = -22:26:40.32 These coordinates are within the FXT X-ray uncertainty region, making this source the likely afterglow of EP250223a. The source has an AB magnitude r = 19.7, calibrated against nearby Pan-STARRS objects. Further observations are in progress. View this GCN Circular online at https://gcn.nasa.gov/circulars/39436. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37447] GRB 250223B: Fermi GBM Final Localization
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39435 SUBJECT: GRB 250223B: Fermi GBM Final Localization DATE: 25/02/23 18:43:58 GMT FROM: rhamburg(a)usra.edu The Fermi GBM team reports the detection of a likely SHORT GRB "At 10:19:23.76 UT on 23 February 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250223B (trigger 761998768/250223430). This trigger was initially classified as Unreliable Location by the flight software, but is in fact a GRB. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 3.54, Dec = +43.49(J2000 degrees, equivalent to J2000 00h 14m, +43d 29'), with a statistical uncertainty of 13 degrees. The angle from the Fermi LAT boresight is 56 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223430/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223430/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223430/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/39435. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37446] EP250223a: Global MASTER-Net observations report
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39434 SUBJECT: EP250223a: Global MASTER-Net observations report DATE: 25/02/23 18:36:57 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250223a ( EP Team et al., GCN 39429) errorbox 6703 sec after notice time and 11479 sec after trigger time at 2025-02-23 18:15:54 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 13 deg. The sun altitude is -12.2 deg. The galactic latitude b = -13 deg., longitude l = 232 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2788235 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 11509 | 2025-02-23 18:15:54 | MASTER-SAAO | (06h 31m 54.68s , -22d 37m 59.1s) | C | 60 | 18.4 | 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/39434. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37445] GRB 250221A: VLA radio detection
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39433 SUBJECT: GRB 250221A: VLA radio detection DATE: 25/02/23 18:32:23 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> R. Ricci (U Rome), E. Troja (U Rome) report on behalf of a larger collaboration: We observed the GRB 250221A discovered by Swift/BAT (Caputo et al. GCN 39396) with the Very Large Array at the centre frequency of 10 GHz (X-band) with a bandwidth of 4 GHz at a mid time of 1.95 days after the trigger. A weak source is detected at the target position with a flux density of 63 +/- 9 microJy. Further observations are planned to assess its variability. We thank the VLA staff for promptly executing the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39433. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37444] Fermi GRB 250223A: Global MASTER-Net observations report
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39432 SUBJECT: Fermi GRB 250223A: Global MASTER-Net observations report DATE: 25/02/23 18:31:10 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250223A ( Fermi GBM team, GCN 39430) errorbox 6037 sec after notice time and 6071 sec after trigger time at 2025-02-23 18:17:23 UT, with upper limit up to 17.8 mag. Observations started at twilight. The observations began at zenith distance = 81 deg. The sun altitude is -12.4 deg. The galactic latitude b = -61 deg., longitude l = 358 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2788279 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 6101 | 2025-02-23 18:17:23 | MASTER-SAAO | (21h 30m 33.95s , -55d 53m 54.3s) | C | 60 | 16.5 | 6180 | 2025-02-23 18:18:42 | MASTER-SAAO | (21h 44m 51.61s , -55d 55m 08.8s) | C | 60 | 16.9 | 6260 | 2025-02-23 18:20:01 | MASTER-SAAO | (21h 48m 30.70s , -54d 02m 03.5s) | C | 60 | 16.9 | 6339 | 2025-02-23 18:21:20 | MASTER-SAAO | (22h 02m 01.64s , -54d 00m 54.6s) | C | 60 | 17.2 | 6419 | 2025-02-23 18:22:40 | MASTER-SAAO | (21h 57m 39.63s , -55d 54m 33.4s) | C | 60 | 17.4 | 6498 | 2025-02-23 18:23:59 | MASTER-SAAO | (22h 11m 47.32s , -55d 55m 37.0s) | C | 60 | 17.8 | 6577 | 2025-02-23 18:25:18 | MASTER-SAAO | (22h 06m 14.56s , -52d 07m 28.6s) | C | 60 | 17.5 | 6656 | 2025-02-23 18:26:38 | MASTER-SAAO | (22h 19m 06.47s , -52d 08m 45.6s) | C | 60 | 17.8 | 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/39432. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37443] Fermi trigger No 762020305: Global MASTER-Net observations report
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39431 SUBJECT: Fermi trigger No 762020305: Global MASTER-Net observations report DATE: 25/02/23 16:46:54 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB250223.68 (trigger No 762020305,17h 30m 28.80s , +41d 02m 24.0s, R=5.1) errorbox 569 sec after notice time and 603 sec after trigger time at 2025-02-23 16:28:23 UT, with upper limit up to 16.6 mag. The observations began at zenith distance = 74 deg. The sun altitude is -47.4 deg. The galactic latitude b = 32 deg., longitude l = 66 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2788242 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 632 | 2025-02-23 16:28:23 | MASTER-Tunka | (17h 31m 26.47s , +40d 50m 52.7s) | C | 55 | 15.9 | 687 | 2025-02-23 16:28:23 | MASTER-Tunka | (17h 31m 26.50s , +40d 50m 52.7s) | C | 165 | 16.5 | Coadd 691 | 2025-02-23 16:29:22 | MASTER-Tunka | (17h 31m 26.58s , +40d 50m 54.0s) | C | 55 | 16.1 | 749 | 2025-02-23 16:30:21 | MASTER-Tunka | (17h 31m 26.76s , +40d 50m 55.4s) | C | 55 | 16.6 | 810 | 2025-02-23 16:31:19 | MASTER-Tunka | (17h 31m 27.02s , +40d 50m 55.5s) | C | 60 | 14.9 | 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/39431. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37442] GRB 250223A: Fermi GBM Final Real-time Localization
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39430 SUBJECT: GRB 250223A: Fermi GBM Final Real-time Localization DATE: 25/02/23 16:46:39 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely SHORT GRB At 16:36:11 UT on 23 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250223A (trigger 762021376.807148 / 250223692). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 340.6, Dec = -40.3 (J2000 degrees, equivalent to J2000 22h 42m, -40d 17'), with a statistical uncertainty of 31.6 degrees. The angle from the Fermi LAT boresight is 95.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223692/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223692/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250223692/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39430. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37441] EP250223a: Einstein Probe detection of an X-ray transient
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39429 SUBJECT: EP250223a: Einstein Probe detection of an X-ray transient DATE: 25/02/23 16:22:43 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Y. Lian, W. J. Zhang (NAOC, CAS), Y. Wang (PMO, CAS), X. Tian (GXU), R. Z. Li(YNAO, CAS), H. W. Pan (NAOC, CAS) report on behalf of the Einstein Probe 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 EP250223a. The transient triggered EP-WXT (ID: 01709131863) at 2025-02-23T15:04:35.749 (UTC). The WXT position of the source is R.A. = 98.258 deg, DEC = -22.432 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 cirlce, an uncatalogued X-ray source was detected at R.A. = 98.2722 deg, DEC = -22.4442 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/39429. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37440] LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39428 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches DATE: 25/02/23 15:10:32 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed an additional search [1] for track-like muon neutrino events consistent with the sky localization of gravitational-wave candidate S250206dm in a time range of -0.1 day, +14 days from the alert event time (2025-02-06 19:01:30.439 UTC to 2025-02-20 21:25:30.439 UTC). During this time period IceCube was collecting good quality data. In this case, we report a p-value of 0.85, consistent with no significant excess of track events. IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE) to neutrino point sources within the locations spanned by the 90% spatial containment of the 7-Update map ranges from 0.028 to 1.010 GeV cm^-2 in this time window. Searches for track-like muon neutrino events detected by IceCube consistent with the 7-Update skymap in a time range of 1000 seconds centered on the alert event time (2025-02-06 21:17:10.436 UTC to 2025-02-06 21:33:50.436 UTC) were also performed using two hypothesis tests. [1,2]. The first search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW skymap. The second uses a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the significance estimate [3]. For these searches we report an overall p-value of 0.021 for the generic transient search and 0.044 for the Bayesian search using the 7-Update map. These p-values measure the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not trials corrected for multiple GW events). These results are updated since GCN 39176 with the updated skymap. Further details are available at https://gcn.nasa.gov/missions/icecube. Additional details and updates will be posted at https://roc.icecube.wisc.edu/public/LvkNuTrackSearch/. 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] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [2] M. G. Aartsen et al 2020 ApJL 898 L10 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017 View this GCN Circular online at https://gcn.nasa.gov/circulars/39428. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37439] GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39427 SUBJECT: GRB 250221A: continued Assy optical observations, brightening afterglow confirmation DATE: 25/02/23 11:51:11 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE, IKI), V. Kim (FAI), M. Krugov (FAI), Y. Aimuratov (FAI), A. Volnova(IKI), A. Pozanenko (IKI) report on behalf of IKI GRB FuN: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCNs 39422,39424; Ghosh et al., GCN 39425) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-20 telescope of Assy-Turgen observatory starting on 2025-02-22 (UT) 15:01:45 in r' filter. The afterglow is clearly detected. Preliminary photometry of the afterglow in the stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) 2025-02-22 15:01:45 1.49280 45x60 r' 20.50 0.05 22.7 The photometry is based on nearby PS1 stars. Compared to our previous observations (Pankov et al., GCNs 39422, 39424, 39426) we can confirm the afterglow brightening. We can estimate the time of the maximum earlier than 2025-02-22 (UT) 12:29:44 View this GCN Circular online at https://gcn.nasa.gov/circulars/39427. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37438] GRB 250221A: continued Mondy optical observations, brightening afterglow
by GCN Circulars 23 Feb '25

23 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39426 SUBJECT: GRB 250221A: continued Mondy optical observations, brightening afterglow DATE: 25/02/23 11:47:30 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunlo (ISZF), A. Volnova (IKI) report on behalf of IKI GRB FuN: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCNs 39422,39424; Ghosh et al., GCN 39425) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-33IK telescope of Mondy observatory starting on 2025-02-22 (UT) 12:29:44 in R filter. The afterglow is clearly detected. Preliminary photometry of the afterglow in the stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) 2025-02-22 12:29:44 1.38790 18x120 R 19.95 0.05 21.6 The photometry is based on nearby USNO-B1.0 (R2) stars. Compared to our previous observations (Pankov et al., GCNs 39422,39424) the afterglow has apparently become brighter. View this GCN Circular online at https://gcn.nasa.gov/circulars/39426. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37437] GRB 250221A: Optical counterpart detection by LCO.
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39425 SUBJECT: GRB 250221A: Optical counterpart detection by LCO. DATE: 25/02/22 15:06:17 GMT FROM: ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994(a)gmail.com> Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration. We observed the field of the GRB 250221A triggered by Swift (Caputo et al., GCN 39396) in B, r filters of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Cerro Tololo Interamerican Observatory, Chille. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). Observations began on February 21, 2025, starting 22.46 hours after the GRB trigger. We clearly detect the optical transient (OT) reported by GCNs ( Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCN 39422; Pankov et al., GCN 39424) in our B, r band image. |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ---------------------------------------------------------------------------------------------------- 2025-02-22 02:02:15.36 22.46 1 x 1200 B B = 21.91 +/- 0.06 2025-02-22 02:10:02.78 22.59 1 x 900 r r = 20.85 +/- 0.06 ---------------------------------------------------------------------------------------------------- The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39425. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37436] GRB 250221A: Mondy optical observations
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39424 SUBJECT: GRB 250221A: Mondy optical observations DATE: 25/02/22 12:25:53 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunlo (ISTP), A. Volnova (IKI) report on behalf of IKI GRB FuN: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCN 39422) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-33IK telescope of Mondy observatory starting on 2025-02-21 (UT) 12:25:52 in R filter. The afterglow is clearly detected. Preliminary photometry of the afterglow in the stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) 2025-02-21 12:25:52 0.38490 23x60 R 20.30 0.05 22.5 The photometry is based on nearby USNO-B1.0 (R2) stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/39424. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37435] Konus-Wind detection of GRB 250221A
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39423 SUBJECT: Konus-Wind detection of GRB 250221A DATE: 25/02/22 12:13:42 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaya, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report GRB 250221A (Swift detection: Caputo et al., GCN 39396) was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~12 sigma count-rate increase in the interval from T0-1.5 s to T0+4.4 s where T0 = T0(BAT) = 03:34:37 UT. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250221A/ Modeling the time-integrated spectrum of the burst by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.05 (-0.12, + 0.12) and Ep = 242(-22,+26) keV. In the 10 keV -10 MeV band, standard for the KW analysis, the burst fluence is (1.67 ± 0.09)x10^-6 erg/cm^2 and the 2.944 s peak energy flux is (2.97 ± 0.17)x10^-7 erg/cm^2/s. Assuming the redshift z=0.768 (Palmerio et al., GCN 39418) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (2.8 ± 0.2)x10^51 erg, the isotropic peak luminosity L_iso to (8.6 ± 0.5)x10^50 erg/s, and the rest-frame peak spectral energy Ep,z to (428 ± 44) keV. With the obtained estimates, GRB 250221A is a hard-spectrum outlier (lies outside 90% prediction bands) of both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250221A/GRB250221A_rest_frame.pdf 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/39423. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37434] GRB 250221A: Assy optical observations
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39422 SUBJECT: GRB 250221A: Assy optical observations DATE: 25/02/22 11:10:50 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex(a)gmail.com> N. Pankov (HSE, IKI), V. Kim (FAI), M. Krugov (FAI), Y. Aimuratov (FAI), A. Volnova(IKI), A. Pozanenko (IKI) report on behalf of IKI GRB FuN: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418) of the Swift GRB 250221A (Caputo et al., GCN 39396) with AZT-20 telescope of Assy-Turgen observatory starting on 2025-02-21 (UT) 15:25:09.55 in r' filter. The afterglow is clearly detected. Preliminary photometry of the OT in the stacked image is the following Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) 2025-02-21 15:25:09 0.50385 30x60 r' 20.90 0.05 22.8 The photometry is based on nearby PS1 stars. View this GCN Circular online at https://gcn.nasa.gov/circulars/39422. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37433] EP250220a: FTW optical and NIR observations and upper limits
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39421 SUBJECT: EP250220a: FTW optical and NIR observations and upper limits DATE: 25/02/22 11:03:18 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU) and Antonella Palmese (Carnegie Mellon U.) report: We observed the 90% EP-FXT localization area of EP250220a (Wang et al., GCN 39387; Hu et al., GCN 39420) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i and J band simultaneously for 59 x 180 s starting at 2025-02-20T22:20:37 UT (0.84 days after the trigger) and 2025-02-21T20:54:36 UT (1.78 days after the trigger). We performed difference imaging with templates from the DESI Legacy Surveys in the r band and templates from PS1 in the i band as well as between our two epochs. We detect no new or evolving source in the EP-FXT localization area. The three sigma mean depths of our observations in the r band are 2025-02-20: r > 25.0 mag 2025-02-21: r > 24.4 mag. This is consistent with the non-detections by Lipunov et al. (GCN 39338), Zhang et al. (GCN 39393), Eyles-Ferris et al. (GCN 39401), Guo et al. (GCN 39402) and Bochenek and Perley (GCN 39408). The magnitudes are calibrated against the PS1 catalog and provided in the AB system. They are not corrected for Galactic extinction. We thank Michael Schmidt from the staff of the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39421. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37432] EP250220a: EP-FXT follow-up observations
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39420 SUBJECT: EP250220a: EP-FXT follow-up observations DATE: 25/02/22 08:11:55 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu (PMO, CAS), Y. L. Wang (NAOC, CAS), P. Y. Han, C. X. Zhang (HUST), B. B. Zhang (BNU), Y. Liu (NAOC, CAS) report on behalf of the Einstein Probe team: Following the detection of the fast X-ray transient EP250220a (Wang et al., GCN 39387), we performed two follow-up observations with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The first FXT observation started at 2025-02-20 14:59:57 (UTC), about 13 hours after the WXT detection, with an exposure of ~ 3 ks. Within the WXT error circle, one faint X-ray source was detected by one of the FXT modules, at the position of R.A. = 113.4516 deg, DEC = 39.8098 deg (J2000), with an uncertainty of 10 arcsec in radius (90% C. L. statistical and systematic). The detection is relatively weak and the spectrum is not well fitted. The second FXT observation started at 2025-02-21 10:12:09 (UTC), about 32 hours after the WXT detection, with an exposure of ~ 7 ks. No source was detected within the WXT error circle. Assuming a photon index of 1.1 and Galactic absorption with NH = 7.13 x 10^20 cm^-2, we derive an upper limit of 1.90e-14 erg/s/cm^2 (0.5-10 keV; 90% C. L.). 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/39420. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37431] GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39419 SUBJECT: GRB 250219A: NUTTelA-TAO / BSTI Optical Limits DATE: 25/02/22 07:47:55 GMT FROM: Toktarkhan Komesh at Nazarbayev University <toktarkhan.komesh(a)nu.edu.kz> T. Komesh (NU), Z. Abdullayev (NU), Z. Maksut (NU), D. Berdikhan (NU), B. Grossan (UCB, NU), M. Krugov (FAI) and E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory: We imaged the field of GRB 250219A with the Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) starting at 21:54:17 UT on 2025-02-19, 6.0 hours after the SVOM/ECLAIRs trigger (F. Daigne et al., GCN 39376). Observations were made in clear conditions. No source consistent with the XRT (J. A. Kennea et al., GCN 39379) was detected. We report the following results: start time t-t0 (minute) end time UL g' UL r' exposure_time (s) ------------ -------------------------------------------------- 21:54:17 361 21:55:17 19.29 19.09 60 21:58:38 365 22:02:38 19.57 19.49 240 t is the middle time, t0 is the SVOM/ECLAIRs trigger time, t-t0 is given in minutes. UL gives the 5 sigma upper limit sensitivity in magnitudes, for images of the given exposure time. Calibration was done with 4 Pan-STARRS catalog stars on our images. No color or other corrections were applied to the values above. ----------------------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/39419. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37430] GRB 250221A: VLT/X-shooter redshift z = 0.768
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39418 SUBJECT: GRB 250221A: VLT/X-shooter redshift z = 0.768 DATE: 25/02/22 04:24:41 GMT FROM: J. T. Palmerio at CEA-Saclay <jesse.palmerio(a)obspm.fr> J. T. Palmerio (CEA/Irfu), A. Saccardi (CEA/Irfu), B. Rayson (U. Leicester), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. J. Levan (Radboud and Warwick), N. R. Tanvir (U. Leicester) report on behalf of the Stargate collaboration: We observed the optical afterglow (Francile et al., GCN 39395; Caputo et al., GCN 39396; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Cotter et al. GCN 39413) of GRB 250221A (Caputo et al., GCN 39396) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and consist of 4x600 s exposures. The slit’s position angle was set to cover the afterglow position as well as the nearby object to the NW (Watson et al., GCN 39397; Cotter et al. GCN 39413). The observation mid time was 2025 Feb 22.08 UT (~22.5 hr after the GRB). In a preliminary reduction of the spectra, we detect two blended traces, corresponding to the afterglow and to the NW object. Spatially consistent with the afterglow position, we detect emission lines of H alpha, [O III] 5007, [O III] 4959, H beta, [O II] 3726/3729 at a common redshift of z = 0.768. In the UBV arm, the trace is dominated by the afterglow continuum. Absorption features are detected corresponding to Mg II and Fe II, at a consistent redshift, which we suggest is the redshift of the burst. We should note the presence of a possible, weak emission feature at 16,588 AA at the position of the afterglow trace. We are not able to identify this feature presently and a full reduction of the data is required to ascertain its reality. At the position of the NW object, a faint, red continuum is detected in the VIS and NIR arms. No clear emission or absorption features are detected, and at the moment we can not provide a redshift determination for this object. We thank Alan Watson (UNAM) for providing us with accurate coordinates of the afterglow. We acknowledge expert support from the ESO staff in Paranal, in particular Francesca Lucertini and Rodrigo Palominos. View this GCN Circular online at https://gcn.nasa.gov/circulars/39418. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37429] GRB 250221A: GRANDMA/TAROT Detection
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39417 SUBJECT: GRB 250221A: GRANDMA/TAROT Detection DATE: 25/02/22 03:00:44 GMT FROM: Heather N. Muenter at UMN <hmuenter000(a)gmail.com> H. Muenter (UMN), F. Magnani (CPPM), S. Antier (OCA/IJCLAB), Y. Rajabov (UBAI), C. Andrade (UMN), A. Klotz (IRAP), C. Limonta, Q. Andre, A. Durroux (OCA), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), P-A. Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS) on behalf of the GRANDMA collaboration: We imaged the field of GRB 250221A detected by SWIFT (GCN 39396) with the TAROT robotic telescope located at the European Southern Observatory, La Silla observatory, Chile. The first image was taken 45 s post T0 and without filter is trailed (see the description in Klotz et al., 2006, A&A 451, L39). We detect the UVOT optical transient at r-mag 17 +/- 0.1 mag, 1.95 min post T0. We continuously detected the source for the first 30 min. All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 and PS1 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/39417. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37428] Fermi trigger No 761805304: Global MASTER-Net observations report
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39416 SUBJECT: Fermi trigger No 761805304: Global MASTER-Net observations report DATE: 25/02/22 02:32:22 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250221.19 (trigger No 761805304,21h 13m 43.92s , -33d 13m 58.8s, R=10.22) errorbox 78509 sec after notice time and 78547 sec after trigger time at 2025-02-22 02:24:07 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 78 deg. The sun altitude is -24.1 deg. The galactic latitude b = -44 deg., longitude l = 12 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2784950 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 78578 | 2025-02-22 02:24:07 | MASTER-SAAO | (20h 37m 17.51s , -38d 45m 28.5s) | C | 60 | 17.8 | 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/39416. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37427] Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39415 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 761867337/250221909 is not a GRB DATE: 25/02/22 01:10:05 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 761867337/250221909 at 21:48:52.46 UT on 21 February 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/39415. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37426] GRB 250221A: Swift-XRT refined Analysis
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39414 SUBJECT: GRB 250221A: Swift-XRT refined Analysis DATE: 25/02/22 00:09:17 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), R. Brivio (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.0 ks of XRT data for GRB 250221A, from 107 s to 66.9 ks after the BAT trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=1.06 (+/-0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.09 (+0.24, -0.23). The best-fitting absorption column is 1.4 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 3.7 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 3.3 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 3.7 x 10^20 cm^-2 Excess significance: 2.7 sigma Photon index: 2.09 (+0.24, -0.23) If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 2.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x 10^-14 (1.1 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01290305. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39414. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37425] GRB 250221A: NOT optical observations
by GCN Circulars 22 Feb '25

22 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39413 SUBJECT: GRB 250221A: NOT optical observations DATE: 25/02/22 00:06:03 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> L. Cotter (UCD), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. Palmerio (CEA/Irfu), A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the optical afterglow (Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412) of the Swift GRB 250221A (Caputo et al., GCN 39396), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the griz filters. The afterglow is well detected in all filters. In a single r-band observation with mid-time 2025 Feb 21.86 UT (17.07 hr after the trigger), we measure for the afterglow r = 22.0 +- 0.15 AB, calibrated against nearby Pan-STARRS objects. Our measurement is affected by the presence of a nearby object about 1" to the NW, visible in the Legacy Survey (Watson et al., GCN 39397). More accurate photometry can be attained via template subtraction. The nearby object has a photometric redshift z = 0.34 +- 0.08 (Zhou et al. 2021, doi:10.1093/mnras/staa3764). The relationship between this object and the GRB is unclear at the moment. We thank Alan Watson (UNAM) for providing us with accurate coordinates of the afterglow. We also thank the observers at the NOT for securing our data, in particular Linda Lombardo, Annika Schichtel, Clara Peter, Diego Mederos Leber, Svenja Heil, and Nina Caviziel (all Goethe University Frankfurt). View this GCN Circular online at https://gcn.nasa.gov/circulars/39413. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37424] GRB 250221A: 1.6m Mephisto optical detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39412 SUBJECT: GRB 250221A: 1.6m Mephisto optical detection DATE: 25/02/21 18:35:37 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Helong Guo, Guowang Du, Xinlei Chen, Xiaotong Chen, Yiheng Xie, Brajesh Kumar, Yuan Fang, Xingzhu Zou, Yu Pan (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Yuanpei Yang, Jinghua Zhang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of Mephisto Team: Simultaneous multi-band photometric observations of the Swift GRB 250221A (Caputo et al., GCN 39396; Beardmore et al., GCN 39404) was performed with 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. The observations were started from 11:55:52 2025-02-21 UT (~8.35 hr after the trigger) and several frames with different exposure time were obtained in uvgr bands. The afterglow candidate (Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409) is clearly detected in the stacked images of g and r band but not in u and v bands. The preliminary magnitudes and 3-sigma upper limits are below: Start_Time(UT) Filter Exp(sec) Mag/LimMag(AB) 2025-02-21T11:55:53 u 120*4, 300*3 >22.20 2025-02-21T12:05:54 v 120*3, 300*3 >22.61 2025-02-21T11:55:52 g 120*4, 300*3 21.57 +/- 0.26 2025-02-21T12:05:54 r 120*3, 300*3 20.87 +/- 0.13 ---------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ---------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39412. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37423] LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39411 SUBJECT: LIGO/Virgo/KAGRA S250221gb: Retraction of GW compact binary merger candidate DATE: 25/02/21 18:19:53 GMT FROM: Isaac McMahon at University of Zurich <isaac.mcmahon(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250221gb is no longer considered to be a candidate of interest: there was a transient noise glitch in the LIGO Hanford detector. View this GCN Circular online at https://gcn.nasa.gov/circulars/39411. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37422] GRB 250221A: AKO Optical Upper Limit
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39410 SUBJECT: GRB 250221A: AKO Optical Upper Limit DATE: 25/02/21 16:45:15 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi, Nuha Manal Pattani, and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of GRB 240221A (Swift BAT and XRT team, Caputo et al. GCN 39396, Beardmore et al., GCN 39404; Shilling et al., GCN 39409; COLIBRÍ/DDRAGO, Watson et al. GCN 39397; REM, Melandri et al. GCN 39406) with our 0.36m f/7.7 robotic telescope. The observation was performed on 21 February 2025 at 15:53: 37 UTC (mid-time), 12.32 hours after the trigger. We obtained 11x180s images using Ic filter at the position given by Swift/XRT: RA (J2000): 03h 57m 51.09s Dec (J2000): -15d 08' 00.6" We did not detect an afterglow candidate at the above position down to a magnitude of Ic = 19.7 for the stacked images. The magnitude was estimated using the Atlas catalogue as a reference. The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39410. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37421] GCN Announcement: New SVOM Notices, Planned Retirement of VOEvent Brokers
by GCN Announcements 21 Feb '25

21 Feb '25

The GCN Team is pleased to announce new features on https://gcn.nasa.gov. SVOM VOEvent Notices Available Over Kafka The SVOM Team and the GCN team are pleased to announce the availability of SVOM notice types via the new GCN in VOEvent format. These notices can be streamed via Kafka. They are not available via GCN Classic. The SVOM Team plans to add JSON format notices at a later date. SVOM Mission Summary: The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese mission, result of a collaboration between the two national space agencies, China National Space Administration (CNSA) and Centre national d'études spatiales (CNES). SVOM mission is dedicated to the study of the most powerful transient phenomena, with a particular emphasis on gamma-ray bursts (GRBs). The SVOM spacecraft carries four multi-wavelength instruments: ECLAIRs, Gamma Ray burst Monitor (GRM), Microchannel X-ray Telescope (MXT) and Visual Telescope (VT). Notice topics: new SVOM notices provide GRB detection and follow-up observation details. Each of the four instruments has its own dedicated topic to stream notices with their related information, see table below: - gcn.notices.svom.voevent.grm - gcn.notices.svom.voevent.eclairs - gcn.notices.svom.voevent.mxt - gcn.notices.svom.voevent.vt A more extensive description of the information provided in these new notices is available at https://gcn.nasa.gov/missions/svom. Planned Retirement of GCN Classic VOEvent Brokers The result of the November 2024 user survey of those utilizing the GCN VOEvent Brokers to receive VOEvent-format Notices with the VOEvent Transport Protocol is overwhelmingly in favor of retiring the brokers and users migrating to receive VOEvent Notices over Kafka. This service is already available for all GCN Classic Notice types with self-subscription via the Start Streaming Notices Guide. The GCN Classic VOEvent brokers will be retired shortly after the conclusion of the O4 gravitational wave network observing run, currently scheduled for October 7, 2025. We recommend the following actions for users currently utilizing VOEvent via GCN Classic. - Sign up to receive VOEvent format Notices via Kafka or email - Let the GCN Team know when you're ready to unsubscribe from receiving them via the GCN Classic brokers. All GCN Classic VOEvent subscribers will be unsubscribed after the end of O4 and the brokers will be taken offline. For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37420] GRB 250221A: Swift/UVOT Detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39409 SUBJECT: GRB 250221A: Swift/UVOT Detection DATE: 25/02/21 15:27:39 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S.P.R. Shilling (Lancaster U.), A.A. Breeveld (UCL-MSSL) and R. Caputo (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250221A 107 s after the BAT trigger (Caputo et al., GCN Circ. 39396). A source consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 39404) is detected in the initial UVOT exposures and appears to be fading. An optical candidate in this field is also detected by Watson et al., (GCN Circ. 39397) and by Melandri et al., (GCN Circ. 39406). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 127 277 147 17.52 +/- 0.04 white 620 639 19 18.41 +/- 0.17 v 107 118 10 17.10 +/- 0.32 v 4484 4683 197 >18.8 b 595 615 19 >18.7 u 340 590 245 17.78 +/- 0.07 w1 4894 5041 144 >19.0 m2 4689 4889 197 >18.6 w2 4279 4479 197 >18.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.332 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39409. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37419] EP250220a: Liverpool Telescope upper limits
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39408 SUBJECT: EP250220a: Liverpool Telescope upper limits DATE: 25/02/21 14:53:53 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of the fast X-ray transient EP250220a (Wang et al., GCN 39387) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x90s exposures in the SDSS r’ and i’ filters starting at 2025-02-20 21:40:49.049 UT, approximately 19.5 hours after the trigger. The images were stacked and the background was subtracted relative to Pan-STARRS-1, as well as Legacy Sky Survey reference imaging using PSF matching with the help of PSFEx. We do not detect any new object at the EP/WXT error region of the transient: the 3-sigma limiting magnitudes on the stacked images are r > 21.7 mag and i > 21.8 mag, in line with Zhang et al. (GCN 39393), Fan et al. (GCN 39400), Eyles-Ferris et al. (GCN 394001) and Guo et al. (GCN 394002). However, we note that there is a bright, saturated star inside the error region, impacting our observations as well as the reference fields. View this GCN Circular online at https://gcn.nasa.gov/circulars/39408. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37418] GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39407 SUBJECT: GRB 250219A: GRANDMA/Kilonova-Catcher upper limits DATE: 25/02/21 14:08:21 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA-Saclay/Irfu), D. Marchais (KNC), M. Freeberg (KNC), C. Andrade(UMN), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250219A (Daigne et al., GCN 39376) detected by SVOM/ECLAIRs with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the T-CAT 0.4m telescope at Crous des Gats Observatory (Cintegabelle, France) and the 0.43m CDK telescope at Alnitak Observatory (Spain) starting from TGRB + 5.8hr. In our stacked frames, we do not detect any optical afterglow at the position reported by Swift/XRT (Kennea et al., GCN 39379), SVOM/VT (Xin et al., GCN 39380) and COLIBRÍ (Magnani et al., GCN 39382). We obtain the following 5-sigma (Vega) upper limits: +---------------+-----------+--------+---------+-----------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Mag U.L.| Instrument| +===============+===========+========+=========+===========+ | 6.6 | 119 x 32s | Rc | 20.7 | T-CAT | | 6.6 | 119 x 32s | V | 21.3 | T-CAT | | 6.8 | 10 x 180s | Rc | 20.9 | 0.43m CDK | | 8.5 | 102 x 32s | Rc | 20.8 | T-CAT | | 8.5 | 102 x 32s | V | 21.4 | T-CAT | +---------------+-----------+--------+---------+-----------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/39407. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37417] GRB 250221A: REM optical/NIR afterglow detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39406 SUBJECT: GRB 250221A: REM optical/NIR afterglow detection DATE: 25/02/21 13:50:48 GMT FROM: Andrea Melandri at INAF-OAR <andrea.melandri(a)inaf.it> A. Melandri (INAF-OAR), 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 250221A detected by Swift (Caputo et al., GCN 39396; Beardmore et al., GCN 39404) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 February 21 at 03:35:39 UT (i.e. ~60 s after the Swift trigger), and lasting for about 2 hours. From preliminary photometry we detect the counterpart in the optical and NIR images at the position of the optical afterglow (Watson et al., GCN 39397) with the following early-time magnitudes: r = 16.5 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 70 s after the trigger. H = 14.8 +/- 0.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time t - t0 = 87 s after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39406. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37416] IceCube-250207A: MASTER flaring blazar QSOJ0854+2006
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39405 SUBJECT: IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 DATE: 25/02/21 11:20:59 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> with Zhirkov effect K. Labzina, K.Zhirkov, V.Lipunov, E.Gorbovskoy, G.Antipov, D.Vlasenko, A.Kuznetsov, N.Tyurina, P.Balanutsa, A.Chasovnikov, D.Kuvshinov, V.Topolev,Ya.Kechin,Yu.Tselik, K.Minkina (Lomonosov Moscow State University, SAI, Physics Department), O.Gress, N.Budnev, O.Ershova (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), 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) MASTER600-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University; Lipunov, Kornilov, Gorbovskoy, Tiurina & Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591, pp.http://www.pereplet.ru/lipunov/625.html#625) started IceCube-250207A (IceCube GCN#39203)of the Ice Cube Alert 250207.09 error box ~11h after trigger time at 2025-02-07 13:53:05 UT, with upper limit up to 19.2 mag. (see cover map: https://master.sai.msu.ru/site/master2/observ.php?id=2770114) We analyzed MASTER archive images since 2010 of the source, that can be related with this event. Global MASTER Net detected QSOJ0854+2006 inside 1 sigma. QSOJ0854+2006 (https://simbad.u-strasbg.fr/simbad/sim-coo) fading to 16.6m during last nights observations. Fortunately, data from the ATLAS network (Tonry et al., 2018, PASP, 13, 164505) are available, which show that ~24 hours before the neutrino alert (05.13 feb 2025.) the blazar QSOJ0854+2006 was at its local standard brightness, it was 1 magnitude brighter: 15.1 . After a few days, the blazar returned to its original bright state. Thus, we report the observation of an Zhirkov effect discovered earlier (The Astrophysical Journal Letters, 896, L19, 2020) . The MASTER archive light curve from 2010 year is available at http://www.pereplet.ru/lipunov/images/ATbbo_galaxy_arhive_midi.jpg View this GCN Circular online at https://gcn.nasa.gov/circulars/39405. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37415] GRB 250221A: Enhanced Swift-XRT position
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39404 SUBJECT: GRB 250221A: Enhanced Swift-XRT position DATE: 25/02/21 10:38:49 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1504 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250221A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 59.46290, -15.13349 which is equivalent to: RA (J2000): 03h 57m 51.09s Dec (J2000): -15d 08' 00.6" with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39404. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37414] LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39403 SUBJECT: LIGO/Virgo/KAGRA S250221eb: Retraction of GW compact binary merger candidate DATE: 25/02/21 10:30:20 GMT FROM: Lorenzo Lunghini <lorenzo.lunghini(a)na.infn.it> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250221eb is no longer considered to be a candidate of interest: there was a transient noise glitch in the LIGO Hanford detector. View this GCN Circular online at https://gcn.nasa.gov/circulars/39403. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37413] EP250220a: 1.6m Mephisto observations
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39402 SUBJECT: EP250220a: 1.6m Mephisto observations DATE: 25/02/21 09:36:39 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Helong Guo, Guowang Du, Xinlei Chen, Xiangkun Liu, Xiaotong Chen, Yiheng Xie, Brajesh Kumar, Yuan Fang, Edoardo P. Lagioia, Yu Pan, Xingzhu Zou, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP250220a detected by EP Team (Wang et al., GCN 39387) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgr band photometric observations were conducted starting from 13:08:36 2025-02-20 UT (~10.93 hr after the trigger) and 3 frames with 300s exposure times were taken. No reliable uncatalogued source was detected in our stacked images, consistent with Zhang et al. (GCN 39393) and Fan et al. (GCN 39400). The 3 sigma upper limits are listed below. Start_Time(UT) | Band | Exp(s)| LimMag (AB) --------------------|------|-------|------------ 2025-02-20T13:33:57 | u | 300*3 | >22.85 2025-02-20T13:08:36 | v | 300*3 | >22.85 2025-02-20T13:33:57 | g | 300*3 | >23.10 2025-02-20T13:08:36 | r | 300*3 | >23.04 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39402. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37412] EP250220a: Liverpool Telescope optical upper limits
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39401 SUBJECT: EP250220a: Liverpool Telescope optical upper limits DATE: 25/02/21 09:31:44 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris, P. T. O’Brien and R. L. C. Starling (U of Leicester) report: We observed the field of the X-ray transient EP250220a (Wang et al., GCN 39387) with the 2m Liverpool Telescope using the IO:O instrument. We obtained 4x100s exposures in the SDSS g’ filter starting at 2025-02-20 22:14:10 UT and 6x100s exposures in the SDSS r’ filter starting at 2025-02-20 22:22:20 UT, approximately 20 hours after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and, due to the crowded field and therefore extensive subtraction artefacts, compared the stacked and reference images manually. Consistent with Zhang et al. (GCN 39393) and Fan et al. (GCN 39400), we identify no new sources within the error region of the EP/FXT candidate. We derive 3-sigma upper limits of g’ > 21.5 and r’ > 21.8 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39401. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37411] EP250220a: Optical upper limit with Kinder observations
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39400 SUBJECT: EP250220a: Optical upper limit with Kinder observations DATE: 25/02/21 08:46:24 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> L. L. Fan (HNAS), A. Aryan (NCU), A. K. H. Kong (NTHU), T.-W. Chen, W.-J. Hou (both NCU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, H.-Y. Hsiao, C.-S. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP250220a (Wang et al., GCN 39387) using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2024, arXiv:2406.09270). The first LOT epoch of observations started at 11:23:50 UTC on the 20th of February 2025 (MJD = 60726.475), about 9.20 hr after the EP WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We do not find any evidence of a new and uncataloged source in the stacked images within the 2.81 arcminute error circle of EP-WXT localization. Moreover, we employed the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction using the "sfft" (Hu, 2022, ApJ, 936, 157) and "hotpants" (Becker A., 2015, ascl.soft. ascl:1504.004) algorithms using a template from Pan-STARRS1 (Chambers et al. 2016, arXiv:1612.05560). We found no evidence of any prominent candidate optical counterpart in the difference image as well. We further employed AutoPhOT to perform the PSF photometry. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 60726.475 | 9.20 | 300 * 6 | > 22.65| 1".12 | 1.13 The non-detection of any optical counterpart in our observations is consistent with Xinglong observations, as reported by Zhang et al. (GCN 39393). The presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.12 mag in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/39400. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37410] SVOM trigger sb25022102 is not an astrophysical event
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39399 SUBJECT: SVOM trigger sb25022102 is not an astrophysical event DATE: 25/02/21 08:39:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), Y. Wang (PMO, CAS), J.-X. Cao, D.-F. Kong (GXU), W.-J. Xie, D.-H. Zhao (NAOC), M. Moita (CEA), L. Zhang (IHEP) report on behalf of the SVOM mission team. At 2025-02-21T02:57:58 SVOM issued an alert with the burst_id sb25022102, see also (Li et al, GCN 39398). This event is no longer considered as an astrophysical event and is likely a false detection due to the presence of Sco X-1 in the edge (partially coded) of the ECLAIRs field of view. We apologize for any inconvenience this may have caused. The Burst Advocate (BA) on shift for this event is R.-Z. Li (YNAO, CAS): liruizhi(a)ynao.ac.cn. Please contact the BA by email if you require any additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/39399. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37409] SVOM/sb25022102: SVOM detection of an X-ray transient
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39398 SUBJECT: SVOM/sb25022102: SVOM detection of an X-ray transient DATE: 25/02/21 04:52:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> R.-Z. Li (YNAO, CAS), Y. Wang (PMO, CAS), J.-X. Cao, D.-F. Kong (GXU), W.-J. Xie, D.-H. Zhao (NAOC), M. Moita (CEA), L. Zhang (IHEP) report on behalf of the SVOM mission team: The SVOM/ECLAIRs telescope triggered and located a soft X-ray transient (SVOM burst-id sb25022102) starting at 2025-02-21T02:57:58.938 UTC (Tb). The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. The burst was detected by the Count-Rate Trigger (CRT) mode and 2 alerts were produced with a best signal-to-noise ratio of 9.66 in the 8-120 keV energy band over a time window of 20.48 second starting at Tb. The localization of the alert is R.A., Dec = 231.472, -17.950 degrees: RA (J2000) = 15:25:53.18 Dec (J2000) = -17:56:58.32 with a 90% C.L. radius of 8.22 arcmin (including systematic error of 2 arcmin added in quadrature). We notice that this error-box contains an X-ray source which could produce such a transient, which is 1RXS J152553.0-174943 in Simbad, located at 7.3 arcmin distance. The SVOM/GRM lightcurve could be find the link below: https://www.bursthub.cn//admin/static/svgrb20250221A.png This trigger reached the slew threshold, hence automatic slew was performed. No X-ray sources were found in the VHF data of SVOM/MXT at 1.22 hours after the trigger. A SVOM ToO has been scheduled. 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. The Burst Advocate (BA) on shift for this burst is R.-Z. Li (YNAO, CAS): liruizhi(a)ynao.ac.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/39398. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37408] GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39397 SUBJECT: GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart DATE: 25/02/21 04:03:03 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Camila Angulo (UNAM), William H. Lee (UNAM), Enrique Moreno Méndez (UNAM), Stéphane Basa (UAR Pytheas), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of Swift/BAT GRB 250221A (Caputo et al., GCN Circ. 39396) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We started observing at 2025-02-21 03:35:56 UTC (80 seconds after the trigger). The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction. In our first two 60 second exposure, we detect a source with i = 17.04 +/- 0.01 There is a much fainter source visible in the Pan-STARRS DR2 at this position. This might be the host galaxy. 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/39397. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37407] GRB 250221A: Swift detection of a burst with an optical counterpart
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39396 SUBJECT: GRB 250221A: Swift detection of a burst with an optical counterpart DATE: 25/02/21 03:53:15 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> R. Caputo (GSFC), C. Gronwall (PSU), R. Gupta (NASA GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. M. Parsotan (GSFC) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 03:34:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250221A (trigger=1290305). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 59.477, -15.139 which is RA(J2000) = 03h 57m 54s Dec(J2000) = -15d 08' 18" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 5 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 03:36:39.9 UT, 122.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 59.46251, -15.13379 which is equivalent to: RA(J2000) = 03h 57m 51.00s Dec(J2000) = -15d 08' 01.6" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 53 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.73 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.1 (+2.63/-2.31) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 340 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 03:57:51.06 = 59.46274 DEC(J2000) = -15:07:59.2 = -15.13311 with a 90%-confidence error radius of about 0.76 arc sec. This position is 2.4 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.82 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.046. Burst Advocate for this burst is R. Caputo (regina.caputo AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37406] Swift GRB250221.15: Global MASTER-Net OT detection
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39395 SUBJECT: Swift GRB250221.15: Global MASTER-Net OT detection DATE: 25/02/21 03:43:44 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina (Lomonosov MSU), O.Gress, N.Budnev(ISU), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), 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 GRB250221.15 60 sec after notice time and 93 sec after trigger time at 2025-02-21 03:36:10 UT. On our first (20s exposure) set we found 1 optical transient within Swift error-box (ra=59.475 dec=-15.1383 r=0.05) brighter than 18.4. T-Tmid Date Time Expt. Ra Dec Mag ---------|---------------------|-------|-----------------|-----------------|------- 103 2025-02-21 03:36:10 20 (03h 57m 51.13s , -15d 08m 00.7s) 16.5 The 5-sigma upper limit has been about 18.4mag The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39395. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37405] Swift GRB250221.15: Global MASTER-Net observations report
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39394 SUBJECT: Swift GRB250221.15: Global MASTER-Net observations report DATE: 25/02/21 03:42:25 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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 Swift GRB250221.15 (trigger No 1290305,03h 57m 54.48s , -15d 08m 20.4s, R=0.05) errorbox 57 sec after notice time and 93 sec after trigger time at 2025-02-21 03:36:10 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 71 deg. The sun altitude is -44.9 deg. The galactic latitude b = -45 deg., longitude l = 207 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2784839 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 103 | MASTER-OAFA | C | 20 | 18.9 | 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/39394. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37404] EP250220a: Xinglong optical upper limit
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39393 SUBJECT: EP250220a: Xinglong optical upper limit DATE: 25/02/21 02:21:20 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Yu-Zhang(NAOC), Junjie-Jin(NAOC), Haiyang-Mu(NAOC), Feng-Xiao(NAOC), Qi-Zhao(NAOC), Zhou-Fan(NAOC), Hong-Wu(NAOC) report on behalf of a large collaboration: Following the detection of EP250220a by EP-WXT (Y. L. Wang et al., GCN 39387), we observed the field of EP250220a using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 6x600s clear-band frames with a median time of 2025-02-20T12:10:32 i.e., 10 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 2.81 arcmin EP/WXT error circle (Y. L. Wang et al., GCN 39387), down to 5-sigma limiting magnitudes of clear ~ 22.6, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/39393. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37403] Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39392 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 761788229/250220993 is not a GRB DATE: 25/02/21 01:29:45 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 761788229/250220993 at 23:50:24.20 UT on 20 February 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/39392. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37402] GRB 250220B: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Feb '25

21 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39391 SUBJECT: GRB 250220B: Fermi GBM Final Real-time Localization DATE: 25/02/21 00:00:55 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 23:50:24 UT on 20 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250220B (trigger 761788229.197974 / 250220993). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 39.3, Dec = 45.6 (J2000 degrees, equivalent to J2000 02h 37m, 45d 36'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 3.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220993/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220993/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220993/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37401] Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39390 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 761782146/250220923 is not a GRB DATE: 25/02/20 22:35:43 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 761782146/250220923 at 22:09:01.82 UT on 20 February 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/39390. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37400] GRB 250220A: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39389 SUBJECT: GRB 250220A: Fermi GBM Final Real-time Localization DATE: 25/02/20 22:19:28 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 22:09:01 UT on 20 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250220A (trigger 761782146.820828 / 250220923). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 194.6, Dec = -60.9 (J2000 degrees, equivalent to J2000 12h 58m, -60d 53'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 171.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220923/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220923/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250220923/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39389. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37399] EP250220a: Global MASTER-Net observations report
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39388 SUBJECT: EP250220a: Global MASTER-Net observations report DATE: 25/02/20 16:18:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP250220a ( EP Team et al., GCN 39387) errorbox 228 sec after notice time and 49332 sec after trigger time at 2025-02-20 15:54:11 UT, with upper limit up to 12.9 mag. The observations began at zenith distance = 17 deg. The sun altitude is -46.1 deg. The galactic latitude b = 25 deg., longitude l = 179 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2784319 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 49363 | 2025-02-20 15:54:11 | MASTER-Tunka | (07h 33m 25.59s , +40d 01m 57.1s) | C | 60 | 12.9 | 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/39388. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37398] EP250220a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39387 SUBJECT: EP250220a: EP-WXT detection of a fast X-ray transient DATE: 25/02/20 15:47:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. L. Wang (NAOC, CAS), D. F. Hu (PMO, CAS), B. B. Zhang (BNU), P. Y. Han, C. X. Zhang (HUST), Y. Liu (NAOC, CAS) report on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient by EP-WXT, designated EP250220a. The WXT position of the source is R.A. = 113.400 deg, DEC = 39.795 deg (J2000) with an uncertainty of 2.81 arcmin in radius (90% C.L. statistical and systematic). The flare starts from 2025-02-20T02:11:59 (UTC), lasting for about 150 seconds. The average 0.5-4 keV spectrum can be fitted with an absorbed powerlaw model, with NH fixed at the Galactic value of 7.13 x 10^20 cm^-2 and a photon index of 1.8 (-0.9/+1.0). The unabsorbed average 0.5-4 keV flux is estimated to be 5.8 (-2.2/+3.3) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above 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/39387. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37397] Konus-Wind detection of GRB 250217C (short)
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39386 SUBJECT: Konus-Wind detection of GRB 250217C (short) DATE: 25/02/20 14:18:00 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The short-duration GRB 250217C (Fermi-GBM detection: The Fermi GBM team, GCN 39357; Smith, GCN 39367; AstroSat-CZTI detection: Tembhurnikar et al., GCN 39359; IPN triangulation: Kozyrev et al., GCN 39365; SVOM-GRM detection: Wang et al., GCN 39369) triggered Konus-Wind at T0=86086.280 s UT (23:54:46.280). The burst light curve shows a multipeaked structure which starts at ~T0 and has a total duration of ~0.3 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250217_T86086/ As observed by Konus-Wind, the burst had a fluence of 2.76(-0.35,+0.38)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.190 s, of 2.38(-0.47,+0.49)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 4 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.27(-0.49,+0.70), the high energy photon index beta = -1.93(-0.11,+0.09), the peak energy Ep = 116(-26,+40) keV (chi2 = 47/37 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39386. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37396] GRB 250219A: Swift/UVOT Upper Limits
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39385 SUBJECT: GRB 250219A: Swift/UVOT Upper Limits DATE: 25/02/20 10:56:47 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of the SVOM/ECLAIRS-detected burst GRB 250219A (Daigne et al., GCN Circ. 39376) 5.1 ks after the trigger. The afterglow reported by Kennea et al. (GCN Circ. 39379), Xin et al. (GCN Circ. 39380), Magnani et al. (GCN Circ. 39382) and Fu et al. (GCN Circ. 39383) is not detected in the U-band exposures. Preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial summed exposure is: Filter T_start(s) T_stop(s) Exp(s) Mag u 5097 11297 330 >20.1 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.016 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39385. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37395] GRB 250219A: OHP/T193 optical upper limit
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39384 SUBJECT: GRB 250219A: OHP/T193 optical upper limit DATE: 25/02/20 10:49:09 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), M. Dennefeld (IAP/CNRS/Sorbonne U.), J. P. Palmerio (CEA/Irfu), E. Le Floc'h (CEA/Irfu), D. Turpin (CEA/Irfu), S. Basa (UAR Pytheas) report on behalf of a larger collaboration: We observed the field of the GRB 250219A (Daigne et al., GCN 39376) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 7 exposures (1x360s, 1x720s and 5x600s) in the r-band starting at 01:11:32 UT on 2025-02-20 (9.3h after the trigger). In the stacked image, we do not detect any new source at the XRT source #1 position (Evans et al., GCN 39377) down to the following 3-sigma limit: r > 22.68 mag AB This value is consistent with previously reported detections or upper limits on the optical afterglow (Xin et al., GCN 39380; Lagioia et al., GCN 39381; Magnani et al., GCN 39382; Fu et al., GCN 39383). The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard, Yasmine Davis and Alix Freckelton for the MISTRAL observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39384. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37394] GRB 250219A: NOT optical observations
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39383 SUBJECT: GRB 250219A: NOT optical observations DATE: 25/02/20 08:48:49 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> S. Y. Fu (NAOC), J. T. Palmerio (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud Univ.), L. Cotter (UCD), D. Xu (NAOC), B. Schneider (LAM), B. N. Hauptmann (NOT and DTU Space), A. M. Kadela (NOT and NBI), report on behalf of a larger collaboration: We observed the optical afterglow candidate (Xin et al., GCN 39380; Magnani et al., GCN 39382; see also Kennea et al., GCN 39379) of the SVOM/ECLAIRs GRB 250219A (Daigne et al., GCN 39376). Observations were carried out using the ALFOSC instrument mounted on the Nordic Optical Telescope (NOT). We obtained 3 x 300 s Sloan r-band frames at a median time of 10.16 hr post-burst and 5 x 200 s Sloan z-band frames at a median time of 10.46 hr post-burst. In the stacked r-band image, the afterglow is weakly detected, at coordinates R.A. (J2000) = 11:33:29.18 Dec. (J2000) = +22:42:21.85 with an uncertainty of ~0.3 arcsec, which is consistent with the SVOM/VT counterpart position (Xin et al, GCN 39380). The source had r ~ 23.6 +/- 0.3 mag (AB), calibrated against nearby objects from the Pan-STARRS catalog. The decay between the NOT and the SVOM/VT epochs (see also Magnani et al., GCN 39382) confirms the source is the afterglow of the burst. The source is not detected in the stacked z-band image, down to a limiting magnitude of z ~ 22.2 mag (AB), again calibrated against Pan-STARRS. View this GCN Circular online at https://gcn.nasa.gov/circulars/39383. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37393] GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39382 SUBJECT: GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart DATE: 25/02/20 08:17:18 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Francesco Magnani (CPPM), Alan M. Watson (UNAM), Sarah Antier (OCA), Jean-Grégoire Ducoin (CPPM), Diego López-Cámara (UNAM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the SVOM/ECLAIRs GRB 250219A (Daigne et al., GCN Circ. 39376) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-20 05:19 to 07:41 UTC (13.47 to 15.85 hours after the trigger) and obtained 90 minutes of exposure in the i filter. The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. At the position of the optical afterglow found by Xin et al. (GCN Circ. 39380), close to the uncataloged Swift/XRT source reported by Kennea et al. (GCN Circ. 39379), we detect a source with i = 23.53 +/- 0.21 We cannot yet confirm fading, as none of the previously reported photometry is in the i filter (Xin et al., GCN Circ. 39380; Lagioia et al., GCN Circ. 39381). 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/39382. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37392] GRB 250219A: 1.6m Mephisto optical upper limits
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39381 SUBJECT: GRB 250219A: 1.6m Mephisto optical upper limits DATE: 25/02/20 05:23:35 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Edoardo P. Lagioia, Yu Pan, Xiangkun Liu, Yaosong Yu, Guowang Du, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xinlei Chen, Xingzhu Zou, Yuanpei Yang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu, Jianyan Wei (all NAOC), Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team: The field of GRB 250219A detected by SVOM/ECLAIRs (Daigne et al., GCN 39376) and followed-up by Swift-XRT (Kennea et al. GCN 39379) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgr band photometric observations were conducted starting from 17:08:52 2025-02-19 UT (~1.26 hr after the trigger) and 4 frames with 120s exposure times were taken. There is no detection of the optical candidate (Xin et al. GCN 39380) in the stacked images of uvgr bands. The preliminary photometry and 3 sigma upper limits are listed below. Start_Time(UT) | Band | Exp(s) | LimMag (AB) ---------------------------|--------|------------ 2025-02-19T17:18:46 | u | 120*4 | >22.4 2025-02-19T17:08:52 | v | 120*4 | >22.2 2025-02-19T17:18:46 | g | 120*4 | >22.8 2025-02-19T17:08:52 | r | 120*4 | >22.8 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39381. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37391] GRB 250219A: SVOM/VT optical counterpart
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39380 SUBJECT: GRB 250219A: SVOM/VT optical counterpart DATE: 25/02/20 04:10:03 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, Y. N. Ma, X.H. Han, H.B. Cai, J. Wang, Y. Xu, J.Y. Wei (NAOC), R.Z. Li(YNAO), F. Daigne, M. Gnaoui (IAP) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observations of the GRB 250219A (Daigne et al., GCN 39376) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. With the X band downlinked data, an uncatalogued optical source was clearly detected within the errorbox of Swift/XRT (Kennea et al., GCN 39379) in VT_R and VT_B stacked images, compared to the DESI catalogues. The position is RA= 173.37166 deg, DEC= 22.70598 deg, J2000, corresponds to RA = 11:33:29.2 DEC = +22:42:21.5 Error=0.5 arcsec The source is brightening at the first phase during our observations and the brightness was estimated to be 22.1+/-0.2 mag in AB magnitude in VT_R, and 23.3+/-0.3 mag in AB magnitude in VT_B, at the mid time of 6.71 hours post the burst, with an exposure time of 16*100 seconds. More deep follow-ups are encouraged. 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/39380. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37390] GRB 250219A: Swift-XRT observations
by GCN Circulars 20 Feb '25

20 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39379 SUBJECT: GRB 250219A: Swift-XRT observations DATE: 25/02/20 01:07:10 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J. A. Kennea (PSU), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 250219A, collecting 323 s of Photon Counting (PC) mode data between T0+4.9 ks and T0+11.3 ks. One uncatalogued X-ray source has been detected within the estimated 3-sigma SVOM/ECLAIRs error region (557 arcsec), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 173.3707 = 11:33:28.97 Dec (J2000.0): +22.7056 = +22:42:20.2 Error: 5.2 arcsec (radius, 90% conf.) Count-rate: 0.072 +/- 0.018 ct s^-1 Distance: 317 arcsec from SVOM/ECLAIRs position. Flux: (2.19 +/- 0.54)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021785. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39379. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37389] LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
by GCN Circulars 19 Feb '25

19 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39378 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations DATE: 25/02/19 22:58:12 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov. on behalf of the MSU “Sozvezdie-270” team, report: At the event time (2025-02-06 21:25:30 UTC) of S250206dm (GCN circulars #39175; #39178; #39231) two cubesats of the Moscow University project “Constellation-270” [1] were operating. These are Avion (the DeCoR-1 and DeCoR-2 instruments) and Arcticsat (the DeCoR-2 instrument). The analysis of monitoring data with the available time resolution of ~1 s did not reveal a significant increase in the count rate of all detectors in the time interval 21:22-21:30 UTC. The following 3-sigma upper limits on the flux were obtained (in units of 10^-7 erg/s/cm^2) for the timescales 1s and 5s. Satellite Energy Range Upper Limit(1s) Upper Limit(5s) Avion 30-500 keV 2.3 1.0 Arcticsat 50-500 keV 1.1 0.5 In the calculations we assumed the following source coordinates: RA=38°, Dec=53° (see GCN circulars #39231, #39261) Avion and Arcticsat are the cubesats of the Moscow University project “Constellation-270” [1] launched on 2023 June 27 (Avion) and on 2024 November 5 (Arcticsat). The payload of both cubesats is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV (Avion) and >50 keV (Arcticsat), the time resolution is 0.5s (Avion) and 1 s (Arcticsat). [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/39378. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37388] GRB 250219A: Swift ToO observations
by GCN Circulars 19 Feb '25

19 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39377 SUBJECT: GRB 250219A: Swift ToO observations DATE: 25/02/19 17:16:31 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250219A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021785 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39377. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37387] GRB 250219A: SVOM detection of a burst
by GCN Circulars 19 Feb '25

19 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39376 SUBJECT: GRB 250219A: SVOM detection of a burst DATE: 25/02/19 16:56:22 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> F. Daigne, M. Gnaoui (IAP), N. Dagoneau (CEA), S. Guillot, M. Brunet (IRAP), C.W. Wang (IHEP) on behalf of the SVOM mission team. At 2025-02-19T15:52:48 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250219A (SVOM burst-id sb25021904). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), from which we received 2 alerts. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 14.57 in the [5-8] keV energy band over a time window of 40.96 seconds starting at Tb. The light curve showed a first episode of about 10 s, followed by a possibly related second episode 130 s later, with a duration of about 50 s. The localization of the best alert is R.A., Dec 173.278, 22.684 degrees: RA (J2000) = 11h33m06.69s Dec (J2000) = 22d41m01.24s with a 90% C.L. radius of 5.65 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this burst. A SVOM ToO has been requested. 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 Frédéric Daigne: daigne(a)iap.fr. 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/39376. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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