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

[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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